OX-201-0006-10M00 - VECTRON INTERNATIONAL

DATA SHEET

FemtoClock® NG Octal 

Universal Frequency Translator 8T49N287

General Description

The 8T49N287 has two independent, fractional-feedback PLLs that

can be used as jitter attenuators and frequency translators. It is

equipped with six integer and two fractional output dividers, allowing

the generation of up to 8 different output frequencies, ranging from

8kHz to 1GHz. Four of these frequencies are completely independent

of each other and the inputs. The other four are related frequencies.

The eight outputs may select among LVPECL, LVDS, HCSL or

LVCMOS output levels.

This makes it ideal to be used in any frequency translation

application, including 1G, 10G, 40G and 100G Synchronous

Ethernet, OTN, and SONET/SDH, including ITU-T G.709 (2009) FEC

rates. The device may also behave as a frequency synthesizer.

The 8T49N287 accepts up to two differential or single-ended input

clocks and a crystal input. Each of the two internal PLLs can lock to

different input clocks which may be of independent frequencies. Each

PLL can use the other input for redundant backup of the primary

clock, but in this case, both input clocks must be related in frequency.

The device supports hitless reference switching between input clocks.

The device monitors all input clocks for Loss of Signal (LOS), and

generates an alarm when an input clock failure is detected. Automatic

and manual hitless reference switching options are supported. LOS

behavior can be set to support gapped or un-gapped clocks.

The 8T49N287 supports holdover for each PLL. The holdover has an

initial accuracy of ±50ppB from the point where the loss of all

applicable input reference(s) has been detected. It maintains a

historical average operating point for each PLL that may be returned

to in holdover at a limited phase slope.

The device places no constraints on input to output frequency conver-

sion, supporting all FEC rates, including the new revision of ITU-T Rec-

ommendation G.709 (2009), most with 0ppm conversion error.

Each PLL has a register-selectable loop bandwidth from 1.4Hz to

360Hz.

Each output supports individual phase delay settings to allow

output-output alignment.

The device supports Output Enable inputs and Lock, Holdover and

LOS status outputs.

The device is programmable through an I2C interface. It also

supports I2C master capability to allow the register configuration to

be read from an external EEPROM.

Applications

•OTN or SONET / SDH equipment Line cards (up to OC-192, and

supporting FEC ratios)

•OTN de-mapping (Gapped Clock and DCO mode)

•Gigabit and Terabit IP switches / routers including support of

Synchronous Ethernet

•SyncE (G.8262) applications

•Wireless base station baseband

•Data communications

•100G Ethernet

Features

•Supports SDH/SONET and Synchronous Ethernet clocks

including all FEC rate conversions

• <0.3ps RMS Typical jitter (including spurs), 12kHz to 20MHz

•Operating modes: locked to input signal, holdover and free-run

•Initial holdover accuracy of ±50ppb

•Accepts up to two LVPECL, LVDS, LVHSTL, HCSL or LVCMOS

input clocks

•Accepts frequencies ranging from 8kHz up to 875MHz

•Auto and manual input clock selection with hitless switching

•Clock input monitoring, including support for gapped clocks

•Phase-Slope Limiting and Fully Hitless Switching options to

control output phase transients

•Operates from a 10MHz to 40MHz fundamental-mode crystal

•Generates 8 LVPECL / LVDS / HCSL or 16 LVCMOS output clocks

•Output frequencies ranging from 8kHz up to 1.0GHz (diff)

•Output frequencies ranging from 8kHz to 250MHz (LVCMOS)

•Four General Purpose I/O pins with optional support for status &

control:

•Four Output Enable control inputs may be mapped to any of the

eight outputs

•Lock, Holdover & Loss-of-Signal status outputs

•Open-drain Interrupt pin

•Nine programmable loop bandwidth settings for each PLL from

1.4Hz to 360Hz.

•Optional Fast Lock function

•Programmable output phase delays in steps as small as 16ps

•Register programmable through I2C or via external I2C EEPROM

•Bypass clock paths for system tests

•Power supply modes

VCC / VCCA / VCCO

3.3V / 3.3V / 3.3V

3.3V / 3.3V / 2.5V

3.3V / 3.3V / 1.8V (LVCMOS)

2.5V / 2.5V / 3.3V

2.5V / 2.5V / 2.5V

2.5V / 2.5V / 1.8V (LVCMOS)

•-40°C to 85°C ambient operating temperature

•Package: 56QFN, lead-free (RoHS 6)

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 2 REVISION 5 07/09/15

8T49N287 Block Diagram

IntN Output

Divider

IntN Output

Divider

FracN Output

Divider

FracN Output

Divider

Fractional

Feedback

APLL 0

Fractional

Feedback

APLL 1

Input Clock

Monitoring,

Priority,

Selection

Status Registers

Control Registers

GPIO

Logic

Lock 0

Holdover 0

Lock 1

Holdover 1

OSC

XTAL

÷P0

CLK0

OTP

I2C Master

I2C Slave

Reset

Logic

SCLK

SDATA

Serial EEPROM

LOS

÷P1

CLK1

nINT

IntN

SA0 PLL_BYP

GPIO

nRST

Figure 1. 8T49N287 Functional Block Diagram

8T49N287 DATA SHEET

REVISION 5 07/09/15 3 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Pin Assignment

Figure 2. Pinout Drawing

56-pin, 8mm x 8mm VFQFN Package

nQ1

VCCO1

nRST

nQ0

VCCO0

nINT

VCCA

CAP0_REF

CAP0

PLL_BYP

VCCA

nQ2

VCCO2

GPIO[0]

VCCO3

GPIO[1]

VCCA

CAP1_REF

CAP1

VCC

VCCA

OSCI

OSCO

S_A0

VEE

CLK0

nCLK0

CLK1

nCLK1

VCC

SDATA

SCLK

VCCA

nQ3

GPIO[2]

VCCO4

nQ4

VCCO5

nQ5

VCCO6

nQ6

VCCO7

nQ7

GPIO[3]

8T49N287

123456789

10 11 12 13 14

42 41 40 39 38 37 36 35 34 33 32 31 30 29

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 4 REVISION 5 07/09/15

Pin Description and Pin Characteristic Tables

Table 1. Pin Descriptions

Number Name Type Description

3OSCI ICrystal Input. Accepts a 10MHz-40MHz reference from a clock oscillator or a

12pF fundamental mode, parallel-resonant crystal.

4OSCOO Crystal Output. This pin should be connected to a crystal. If an oscillator is

connected to OSCI, then this pin must be left unconnected.

5 S_A0 I Pulldown I2C lower address bit A0.

12 SDATA I/O Pullup I2C interface bi-directional Data.

13 SCLK I/O Pullup I2C interface bi-directional Clock.

7 CLK0 I Pulldown Non-inverting differential clock input.

8nCLK0I

Pullup /

Pulldown

Inverting differential clock input. VCC/2 when left floating (set by the internal

pullup and pulldown resistors.)

9 CLK1 I Pulldown Non-inverting differential clock input.

10 nCLK1 I Pullup /

Pulldown

Inverting differential clock input. VCC/2 when left floating (set by the internal

pullup and pulldown resistors.)

48, 47 Q0, nQ0 O Universal Output Clock 0. Please refer to the Output Drivers section for more details.

44, 43 Q1, nQ1 O Universal Output Clock 1. Please refer to the Output Drivers section for more details.

27, 28 Q2, nQ2 O Universal Output Clock 2. Please refer to the Output Drivers section for more details.

23, 24 Q3, nQ3 O Universal Output Clock 3. Please refer to the Output Drivers section for more details.

40, 39 Q4, nQ4 O Universal Output Clock 4. Please refer to the Output Drivers section for more details.

37, 36 Q5, nQ5 O Universal Output Clock 5. Please refer to the Output Drivers section for more details.

34, 33 Q6, nQ6 O Universal Output Clock 6. Please refer to the Output Drivers section for more details.

31, 30 Q7, nQ7 O Universal Output Clock 7. Please refer to the Output Drivers section for more details.

46 nRST I Pullup

Master Reset input. LVTTL / LVCMOS interface levels:

0 = All registers and state machines are reset to their default values

1 = Device runs normally

50 nINT OOpen-drain

with pullup Interrupt output.

29, 42, 21, 25 GPIO[3:0] I/O Pullup General-purpose input-outputs. LVTTL / LVCMOS Input levels Open-drain

output. Pulled-up with 5.1k resistor to VCC.

54 PLL_BYP IPulldown

Bypass Selection. Allow input references to bypass both PLLs. 

LVTTL / LVCMOS interface levels.

6, ePad VEE Power Negative supply voltage. All VEE pins and EPAD must be connected before any

positive supply voltage is applied.

11 VCC Power Core and digital functions supply voltage.

17 VCC Power Core and digital functions supply voltage.

2VCCA Power Analog functions supply voltage for core analog functions.

14, 15, 16, 20 VCCA Power Analog functions supply voltage for analog functions associated with PLL1.

1, 51, 55, 56 VCCA Power Analog functions supply voltage for analog functions associated with PLL0.

49 VCCO0 Power High-speed output supply voltage for output pair Q0, nQ0.

45 VCCO1 Power High-speed output supply voltage for output pair Q1, nQ1.

26 VCCO2 Power High-speed output supply voltage for output pair Q2, nQ2.

22 VCCO3 Power High-speed output supply voltage for output pair Q3, nQ3.

8T49N287 DATA SHEET

REVISION 5 07/09/15 5 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

NOTE: Pullup and Pulldown refer to internal input resistors. See Ta bl e 2 , Pin Characteristics, for typical values.

Table 2. Pin Characteristics, VCC = VCCOX = 3.3V±5% or 2.5V±5%

NOTE: VCCOX denotes: VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE 1: This specification does not apply to OSCI and OSCO pins.

41 VCCO4 Power High-speed output supply voltage for output pair Q4, nQ4.

38 VCCO5 Power High-speed output supply voltage for output pair Q5, nQ5.

35 VCCO6 Power High-speed output supply voltage for output pair Q6, nQ6.

32 VCCO7 Power High-speed output supply voltage for output pair Q7, nQ7.

CAP0,

CAP0_REF Analog PLL0 External Capacitance.

CAP1,

CAP1_REF Analog PLL1 External Capacitance.

Symbol Parameter Test Conditions Minimum Typical Maximum Units

CIN Input Capacitance; NOTE 1 3.5 pF

RPULLUP

Internal

Pullup

Resistor

nRST,

SDATA, SCLK 51 k

nINT 50 k

GPIO[3:0] 5.1 k

RPULLDOWN Internal Pulldown Resistor 51 k

CPD

Power

Dissipation

Capacitance

(per output

pair)

LVC M O S;

Q[0:1], Q[4:7] VCCOX = 3.465V 14.5 pF

LVCMOS Q[2:3] VCCOX = 3.465V 18.5 pF

LVC M O S;

Q[0:1], Q[4:7] VCCOX = 2.625V 13 pF

LVCMOS; Q[2:3] VCCOX = 2.625V 17.5 pF

LVC M O S;

Q[0:1], Q[4:7] VCCOX = 1.89V 12.5 pF

LVCMOS; Q[2:3] VCCOX = 1.89V 17 pF

LVDS, HCSL or

LVPECL; 

Q[0:1], Q[4:7]

VCCOx = 3.465V or 2.625V 2 pF

LVDS, HCSL or

LVPECL; Q[2:3] VCCOx = 3.465V or 2.625V 4.5 pF

ROUT

Output

Impedance

GPIO [3:0] Output HIGH 5.1 k

Output LOW 25 

LVC M O S;

Q[0:7], nQ[0:7] 20 

Number Name Type Description

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 6 REVISION 5 07/09/15

Principles of Operation

The 8T49N287 has two PLLs that can each independently be locked

to any of the input clocks and generate a wide range of synchronized

output clocks.

It incorporates two completely independent PLLs. These could be

used for example in the transmit and receive path of Synchronous

Ethernet equipment. Either of the input clocks can be selected as the

reference for either PLL. From the output of the two PLLs a wide

range of output frequencies can be simultaneously generated.

The 8T49N287 accepts up to two differential input clocks ranging

from 8kHz up to 875MHz. It generates up to eight output clocks

ranging from 8kHz up to 1.0GHz.

Each PLL path within the 8T49N287 supports three states: Lock,

Holdover and Free-run. Lock & holdover status may be monitored on

hitless reference switching. In the locked state, the PLL locks to a

valid clock input and its output clocks have a frequency accuracy

equal to the frequency accuracy of the input clock. In the Holdover

state, the PLL will output a clock which is based on the selected

holdover behavior. Each of the PLL paths within the 8T49N287 has

an initial holdover frequency offset of ±50ppb. In the Free-run state,

the PLL outputs a clock with the same frequency accuracy as the

external crystal.

Upon power up, each PLL will enter Free-run state, in this state it

generates output clocks with the same frequency accuracy as the

external crystal. The 8T49N287 continuously monitors each input for

activity (signal transitions).

In automatic reference switching, when an input clock has been

validated the PLL will transition to the locked state. If the selected

input clock fails and there are no other valid input clocks, the PLL will

quickly detect that and go into holdover. In the Holdover state, the

PLL will output a clock which is based on the selected holdover

behavior. If the selected input clock fails and another input clock is

available then the 8T49N287 will hitlessly switch to that input clock.

The reference switch can be either revertive or non-revertive.

The device supports conversion of any input frequency to four

different, independent output frequencies on the Q[0:3]outputs.

Additionally, a further four output frequencies may be generated that

are integer-related to the four independent frequencies. These

additional four frequencies are on the Q[4:7] outputs.

The 8T49N287 has a programmable loop bandwidth from 1.4Hz to

360Hz.

The device monitors all input clocks and generates an alarm when an

input clock failure is detected.

The device supports programmable individual output phase

adjustments in order to allow control of input to output phase

adjustments and output to output phase alignment.

The device is programmable through an I2C and may also

autonomously read its register settings from an internal One-Time

Programmable (OTP) memory or an external serial I2C EEPROM.

Crystal Input

The crystal input on the 8T49N287 is capable of being driven by a

parallel-resonant, fundamental mode crystal with a frequency range

of 10MHz - 40MHz.

The oscillator input also supports being driven by a single-ended

crystal oscillator or reference clock.

The initial holdover frequency offset is set by the device, but the long

term drift depends on the quality of the crystal or oscillator attached

to this port.

Bypass Path

For system test purposes, each of PLL0 and PLL1 may be bypassed.

When PLL_BYP is asserted the CLK0 input reference will be

presented directly on the Q4 output. The CLK1 input reference will be

presented directly on the Q5 output.

Additionally, CLK0 or CLK1 may be used as a clock source for the

output dividers of Q[4:7]. This may only be done for input frequencies

of 250MHz or less.

Input Clock Selection

The 8T49N287 accepts up to two input clocks with frequencies

ranging from 8kHz up to 875MHz. Each input can accept LVPECL,

LVDS, LVHSTL, HCSL or LVCMOS inputs using 1.8V, 2.5V or 3.3V

logic levels. To use LVCMOS inputs, refer to the Application Note,

Wiring the Differential Input to Accept Single-Ended Levels for

biasing instructions.

The device has independent input clock selection control for each

PLL. In Manual mode, only one of these inputs may be chosen per

PLL and if that input fails that PLL will enter holdover.

Manual mode may be operated by directly selecting the desired input

reference in the REFSEL register field. It may also operate via

pin-selection of the desired input clock by selecting that mode in the

REFSEL register field. In that case, GPIOs must be used as Clock

Select inputs (CSELn). CSEL0 = 0 will select the CLK0 input and

CSEL0 = 1 will select the CLK1 input for PLL0. CSEL1 will perform

the same function for PLL1.

In addition, the crystal frequency may be passed directly to the output

dividers for Q[4:7] for use as a reference.

Inputs do not support transmission of spread-spectrum clocking

sources. Since this family is intended for high-performance

applications, it will assume input reference sources to have stabilities

of +100ppm or better, except where gapped clock inputs are used.

If the PLL is working in automatic mode, then each of the input

reference sources is assigned a priority of 1-2. At power-up or if the

currently selected input reference fails, the PLL will switch to the

highest priority input reference that is valid at that time (see section

Input Clock Monitor for details).

8T49N287 DATA SHEET

REVISION 5 07/09/15 7 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Automatic mode has two sub-options: revertive or non-revertive. In

revertive mode, the PLL will switch to a reference with a higher

priority setting whenever one becomes valid. In non-revertive mode

the PLL remains with the currently selected source as long as it

remains valid.

The clock input selection is based on the input clock priority set by the

Clock Input Priority control registers. It is recommended that all input

references for a PLL be given different priority settings in the Clock

Input Priority control registers for that PLL.

Input Clock Monitor

Each clock input is monitored for Loss of Signal (LOS). If no activity

has been detected on the clock input within a user-selectable time

period then the clock input is considered to be failed and an internal

Loss-of-Signal status flag is set, which may cause an input

switchover depending on other settings. The user-selectable time

period has sufficient range to allow a gapped clock missing many

consecutive edges to be considered a valid input.

User-selection of the clock monitor time-period is based on a counter

driven by a monitor clock. The monitor clock is fixed at the frequency

of PLL0’s VCO divided by 8. With a VCO range of 3GHz - 4GHz, the

monitor clock has a frequency range of 375MHz to 500MHz.

The monitor logic for each input reference will count the number of

monitor clock edges indicated in the appropriate Monitor Control

monitored, then the count resets and begins again. If the target edge

count is reached before an input reference edge is received, then an

internal soft alarm is raised and the count re-starts. During the soft

alarm period, the PLL(s) tracking this input will not be adjusted. If an

input reference edge is received before the count expires for the

second time, then the soft alarm status is cleared and the PLL(s) will

resume adjustments. If the count expires again without any input

reference edge being received, then a Loss-of-Signal alarm is

declared.

It is expected that for normal (non-gapped) clock operation, users will

set the monitor clock count for each input reference to be slightly

longer than the nominal period of that input reference. A margin of 2-3

monitor clock periods should give a reasonably quick reaction time

and yet prevent false alarms.

For gapped clock operation, the user will set the monitor clock count

to a few monitor clock periods longer than the longest expected clock

gap period. The monitor count registers support 17-bit count values,

which will support at least a gap length of two clock periods for any

supported input reference frequency, with longer gaps being

supported for faster input reference frequencies. Since gapped

clocks usually occur on input reference frequencies above 100MHz,

gap lengths of thousands of periods can be supported.

Using this configuration for a gapped clock, the PLL will continue to

adjust while the normally expected gap is present, but will freeze

once the expected gap length has been exceeded and alarm after

twice the normal gap length has passed.

Once a LOS on any of the input clocks is detected, the appropriate

internal LOS alarm will be asserted and it will remain asserted until

that input clock returns and will be validated by the receipt of 8 rising

clock edges on that input reference. If another error condition on the

same input clock is detected during the validation time then the alarm

remains asserted and the validation time starts over.

Each LOS flag may also be reflected on one of the GPIO[3:0] outputs.

Changes in status of any reference can also generate an interrupt if

not masked.

Holdover

8T49N287 supports a small initial holdover frequency offset for each

PLL path in non-gapped clock mode. When the input clock monitor is

set to support gapped clock operation, this initial holdover frequency

offset is indeterminate since the desired behavior with gapped clocks

is for the PLL to continue to adjust itself even if clock edges are

missing. In gapped clock mode, the PLL will not enter holdover until

the input is missing for two LOS monitor periods.

The holdover performance characteristics of a clock are referred as

its accuracy and stability, and are characterized in terms of the

fractional frequency offset. The 8T49N287 can only control the initial

frequency accuracy. Longer-term accuracy and stability are

determined by the accuracy and stability of the external oscillator.

When a PLL loses all valid input references, it will enter the holdover

state. In non-gapped clock mode, the PLL will initially maintain its

most recent frequency offset setting and then transition at a rate

dictated by its selected phase-slope limit setting to a frequency offset

setting that is based on historical settings.

This behavior is intended to compensate for any frequency drift that

may have occurred on the input reference before it was detected to

be lost.

The historical holdover value will have three options:

• Return to center of tuning range within the VCO band.

• Instantaneous mode - the holdover frequency will use the

DPLL current frequency 100msec before it entered

holdover. The accuracy is shown in the AC Electrical

Characteristics, Table 11A.

• Fast average mode - an internal IIR (Infinite Impulse

Response) filter is employed to get the frequency offset.

The IIR filter gives a 3 dB attenuation point corresponding to

a nominal period of 20 minutes. The accuracy is shown in

the AC Electrical Characteristics, Table 11A.

When entering holdover, each PLL will set a separate internal HOLD

alarm internally. This alarm may be read from internal status register,

appear on the appropriate GPIO pin and/or assert the nINT output.

While a PLL is in holdover, its frequency offset is now relative to the

crystal input and so the output clocks derived from that PLL will be

tracing their accuracy to the local oscillator or crystal. At some point

in time, depending on the stability & accuracy of that source, the

clock(s) derived from that PLL will have drifted outside of the limits of

the holdover state and the system will be considered to be in a

free-run state. Since this borderline is defined outside the PLL and

dictated by the accuracy and stability of the external local crystal or

oscillator, the 8T49N287 cannot know or influence when that

transition occurs. As a result, the 8T49N287 will remain in the

holdover state internally.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 8 REVISION 5 07/09/15

Input to Output Clock Frequency

The 8T49N287 is designed to accept any frequency in its input range

and generate eight different output frequencies that are independent

from each other and from the input frequencies. The internal

architecture of the device ensures that most such translations will

result in the exact output frequency specified. Where exact frequency

translation is not possible, the frequency translation error will be

minimized.Please contact IDT for configuration software or other

assistance in determining if a desired configuration will be supported

exactly.

Synthesizer Mode Operation

The device may also act as a frequency synthesizer with either or

both PLL's generating their operating frequency from just the crystal

input. By setting the SYN_MODEn register bit and setting the

STATEn[1:0] field to Freerun, no input clock references are required

to generate the desired output frequencies.

Loop Filter and Bandwidth

When operating in Synthesizer Mode as described above, the

8T49N287 has a fixed loop bandwidth of approximately 200kHz.

When operating in all other modes, the following information applies:

The 8T49N287 uses no external components to support a range of

loop bandwidths: 1.40625Hz, 2.8125Hz, 5.625Hz, 11.25Hz, 22.5Hz,

45Hz, 90Hz, 180Hz or 360Hz. Each PLL shall support separate loop

filter settings.

The device supports two different loop bandwidth settings for each

PLL: acquisition and locked. These loop bandwidths are selected

from the list of options described above. If enabled, the acquisition

bandwidth is used while lock is being acquired to allow the PLL to

“fast-lock”. Once locked the PLL will use the locked bandwidth

setting. If the acquisition bandwidth setting is not used, the PLL will

use the locked bandwidth setting at all times.

Output Dividers and Mapping to PLLs

The 8T49N287 will support eight output dividers that may be mapped

to either PLL. Six of the output dividers will have IntN capability only

(see Ta b l e 3 ) and the other two will support FracN division.

Integer Output Divider Programming (Q[0:1], Q[4:7] only)

Each integer output divider block consists of two divider stages in a

series to achieve the desired total output divider ratio. The first stage

divider may be set to divide by 4, 5 or 6. The second stage of the

divider may be bypassed (i.e. divide-by-1) or programmed to any

even divider ratio from 2 to 131,070. The total divide ratios, settings

and possible output frequencies are shown in Table 3.

In addition, the first divider stage for the Q[4:7] outputs supports a

bypass (i.e. divide-by-1) operation for some clock sources.

Table 3. Q[0:1], Q[4:7] Output Divide Ratios

NOTE: Above frequency ranges for Q[4:7] apply when driven directly

from PLL0 or PLL1.

Fractional Output Divider Programming (Q[2:3] only)

For the FracN output dividers Q[2:3], the output divide ratio is given

by:

Output Divide Ratio = (N.F)x2

N = Integer Part: 4, 5, ...(218-1)

F = Fractional Part: [0, 1, 2, ...(228-1)]/(228)

For integer operation of these outputs dividers, N = 3 is also

supported.

Output Divider Frequency Sources

Output dividers associated with the Q[0:3] outputs can take their

input frequencies from either PLL0 or PLL1.

Output dividers associated with the Q[4:7] outputs can take their

input frequencies from PLL0, PLL1, Q2 or Q3 output dividers, CLK0

or CLK1 input frequencies or the crystal frequency.

Output Banks

Outputs of the 8T49N287 are divided into three banks for purposes

of output skew measurement:

• Q0, nQ0, Q1, nQ1

• Q4, nQ4, Q5, nQ5

• Q6, nQ6, Q7, nQ7

1st-Stage

Divide

2nd-Stage

Divide

Total

Divide

Minimum

FOUT MHz

Maximum

FOUT MHz

4 1 4 750 1000

5 1 5 600 800

6 1 6 500 666.7

4 2 8 375 500

5 2 10 300 400

6 2 12 250 333.3

4 4 16 187.5 250

5 4 20 150 200

6 4 24 125 166.7

...

4 131,070 524,280 0.0057 0.0076

5 131,070 655,350 0.0046 0.0061

6 131,070 786,420 0.0038 0.0051

8T49N287 DATA SHEET

REVISION 5 07/09/15 9 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Output Phase Control on Switchover

When the 8T49N287 switches between input references, enters or

leaves the holdover state for either PLL, there are two options on how

the output phase can be controlled in these events: phase-slope

limiting or fully hitless switching (sometimes called phase build-out)

may be selected. The SWMODEn bit selects which behavior is to be

followed for PLLn.

If fully hitless switching is selected, then the output phase will remain

unchanged under any of these conditions. Note that fully hitless

switching is not supported when external loopback is being used.

Fully hitless switching should not be used unless all input references

are in the same clock domain. Note that use of this mode may prevent

an output frequency and phase from being able to trace its alignment

back to a primary reference source.

If phase-slope limiting is selected, then the output phase will adjust

from its previous value until it is tracking the new condition at a rate

dictated by the SLEWn[1:0] bits. Phase-slope limiting should be used

if all input references are not in the same clock domain or users wish

to retain traceability to a primary reference source.

Input-Output Delay Control

When using the 8T49N285 in external loopback or in a situation

where input-output delay needs to be known and controlled, it is

necessary to examine the exact signal path through the device. Due

to the flexibility of the device, there are a large number of potential

signal paths from input to output through it that depend on the desired

configuration. Each of those potential paths may include or exclude

logic blocks from the path and change the absolute value of the delay

(Static Phase Offset or SPO) through the device. Considering the

range of SPO values to cover all those potential paths would not be

useful in achieving the target delays for any specific user

configuration. Please contact IDT for the specific SPO value

associated with a desired input-output path. Note that events such as

switchovers, entering or leaving holdover or re-configuring the signal

path can result in one-time changes to the SPO due to that path

re-configuration. The AC Electrical Characteristics, (Table 11A)

indicates the maximum variation in SPO that could be expected for a

particular path through the device.

Output Phase Alignment

The device has a programmable output to output phase alignment for

each of the eight output dividers. After power-up and the PLLs have

achieved lock, the device will be in a state where the outputs are

synchronized with a deterministic offset relative to each other.After

synchronization, the output alignment will depend on the particular

configuration of each output according to the following rules. The

step size is defined as the period of the clock to that divider:

1) Only outputs derived from the same source will be aligned with

each other. 'Source' means the reference selected to drive the output

divider as controlled by the CLK_SELn bit for each output.

2) For integer dividers (Q[0:1], Q[4:7]) when both divider stages are

active, edges are aligned. This case is used as a baseline to compare

the other cases here.

3) For integer dividers where the 1st-stage divider is bypassed (only

Q[4:7] support this), coarse delay adjustments can’t be performed.

The output phase will be one step earlier than in Case 2.

4) Fractional output dividers (Q2 or Q3) do not guarantee any specific

phase on power-up or after a synchronization event.

5) Integer dividers using Q2 or Q3 as a source (Q[4:7] support this

option) will be aligned to their source divider's output (Q2 or Q3).

Note that the output skews described above are not included in any

of the phase adjustments described here.

Once the device is in operation, the outputs associated with each

PLL may have their phase adjustments re-synced in one of two ways:

1) If the PLL becomes unlocked, the coarse phase adjustments will

be reset and the fine phase adjustments will be re-loaded once it

becomes locked again.

2) Toggling of a register bit for either PLL (PLLn_SYN bits in register

00A8h) may also be used to force a re-sync / re-load for outputs

associated with that PLL.

The user may apply adjustments that are proportional to the period

of the clock source each output divider is operating from. For

example, if the divider associated with Output Q3 is running off PLL0,

which has a VCO frequency of 4GHz, then the appropriate period

would be 250ps. The output phase may be adjusted in these steps

across the full period of the output.

•Coarse Adjustment: all Output Dividers may have their phase

adjusted in steps of the source clock period. For example a 4GHz

VCO gives a step size of 250ps. The user may request an

adjustment of phase of up to 31 steps using a single register write.

The phase will be adjusted by lengthening the period of the output

by 250ps at a time. This process will be repeated every four output

clock periods until the full requested adjustment has been

achieved. A busy signal will remain asserted in the phase delay

adjustment may be setup and triggered by toggling the trigger bit.

•Fine Adjustment: For the Fractional Output Dividers associated

with the Q2 and Q3 outputs, the phase of those outputs may be

further adjusted with a granularity of 1/16th of the VCO period. For

example a 4GHz VCO frequency gives a granularity of 16ps. This

is performed by directly writing the required offset (from the

nominal rising edge position) in units of 1/16th of the output period

into a register. Then the appropriate PLLn_SYN bit must be

toggled to load the new value. Note that toggling this bit will clear

all Coarse Delays for all outputs associated with that PLL, so Fine

Delays should be set first, before Coarse Delays. The output will

then jump directly to that new offset value. For this reason, this

adjustment should be made as the input is initially programmed or

in High-Impedance.

Each output has the capability of being inverted (180° phase shift).

Jitter and Wander Tolerance

The 8T49N287 can be used as a line card device and therefore is

expected to tolerate the jitter and wander output of a timing card PLL

(e.g 82P33714).

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 10 REVISION 5 07/09/15

Output Drivers

The Q0 to Q7 clock outputs are provided with register-controlled

output drivers. By selecting the output drive type in the appropriate

or LVDS logic levels.

The operating voltage ranges of each output is determined by its

independent output power pin (VCCO) and thus each can have

different output voltage levels. Output voltage levels of 2.5V or 3.3V

are supported for differential operation and LVCMOS operation. In

addition, LVCMOS output operation supports 1.8V VCCO.

Each output may be enabled or disabled by register bits and/or GPIO

pins configured as Output Enables. The outputs will be enabled if the

disabled an output will be in a high impedance state.

LVCMOS Operation

When a given output is configured to provide LVCMOS levels, then

both the Q and nQ outputs will toggle at the selected output

frequency. All the previously described configuration and control

apply equally to both outputs. Frequency, phase alignment, voltage

levels and enable / disable status apply to both the Q and nQ pins.

When configured as LVCMOS, the Q and nQ outputs can be selected

to be phase-aligned with each other or inverted relative to one

another. Phase-aligned outputs will have increased simultaneous

switching currents which can negatively affect phase noise

performance and power consumption. It is recommended that use of

this selection be kept to a minimum.

Power-Saving Modes

To allow the device to consume the least power possible for a given

application, the following functions are included under register

control:

• PLL1 may be shut down.

• Any unused output, including all output divider and phase

adjustment logic, can be individually powered-off.

• Clock gating on logic that is not being used.

Status / Control Signals and Interrupts

General-Purpose I/Os & Interrupts

The 8T49N287 provides 4 General Purpose Input / Output (GPIO)

pins for miscellaneous status & control functions. Each GPIO may be

configured as an input or an output. Each GPIO may be directly

controlled from register bits or be used as a predefined function as

shown in Tab l e 4 . Note that the default state prior to configuration

being loaded from internal OTP or external EEPROM will be to set

each GPIO to function as an Output Enable.

Table 4. GPIO Configuration

If used in the Fixed Function mode of operation, the GPIO bits will

reflect the real-time status of their respective status bits as shown in

Ta b l e 4 . Note that the LOL signal represents the lock status of the

PLL. It does not account for the process of synchronization of the

output dividers associated with that PLL. The output dividers

programmed to operate from that PLL will automatically go through a

re-synchronization process when the PLL locks or re-locks, or if the

user triggers a re-sync manually via register bit PLLn_SYN. This

synchronization process may result in a period of instability on the

affected outputs for a duration of up to 350ns after the re-lock (LOL

de-asserts) or the PLLn_SYN bit is de-asserted.

Interrupt Functionality

Interrupt functionality includes an interrupt status flag for each of PLL

Loss-of-Lock Status (LOL[1:0]), PLL Holdover Status (HOLD[1:0])

and Input Reference Status (LOS[1:0]) that is set whenever there is

an alarm on any of those signals. The Status Flag will remain set until

the alarm has been cleared and a ‘1’ has been written to the Status

Flag’s register location or if a reset occurs. Each Status Flag will also

have an Interrupt Enable bit that will determine if that Status Flag is

allowed to cause the Interrupt Status to be affected (enabled) or not

(disabled). All Interrupt Enable bits will be in the disabled state after

reset. The Device Interrupt Status flag and nINT output pin are

asserted if any of the enabled Interrupt Status flags are set.

Device Hardware Configuration

The 8T49N287 supports an internal One-Time Programmable (OTP)

memory that can be pre-programmed at the factory with 1 complete

device configuration. If the device is set to read a configuration from

an external, serial EEPROM, then the values read will overwrite the

OTP-defined values.

This configuration can be over-written using the serial interface once

reset is complete. Any configuration written via the programming

interface needs to be re-written after any power cycle or reset. Please

contact IDT if a specific factory-programmed configuration is desired.

GPIO

Configured as Input Configured as Output

Fixed Function

General

Purpose

Fixed Function

General

Purpose

Output

Enable

(default)

Output

Enable

Clock

Select

3 OE[3] OE[7] CSEL1 GPI[3] - - GPO[3]

2 OE[2] OE[6] CSEL0 GPI[2] LOS[0] LOS[1] GPO[2]

1 OE[1] OE[5] - GPI[1] HOLD[0] HOLD[1] GPO[1]

0 OE[0] OE[4] - GPI[0] LOL[0] LOL[1] GPO[0]

8T49N287 DATA SHEET

REVISION 5 07/09/15 11 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Device Start-up & Reset Behavior

The 8T49N287 has an internal power-up reset (POR) circuit and a

Master Reset input pin nRST. If either is asserted, the device will be

in the Reset State.

For highly programmable devices, it’s common practice to reset the

device immediately after the initial power-on sequence. IDT

recommends connecting the nRST input pin to a programmable logic

source for optimal functionality. It is recommended that a minimum

pulse width of 10ns be used to drive the nRST input pin.

While in the reset state (nRST input asserted or POR active), the

device will operate as follows:

• All registers will return to & be held in their default states as

indicated in the applicable register description.

• All internal state machines will be in their reset conditions.

• The serial interface will not respond to read or write cycles.

• The GPIO signals will be configured as General-Purpose inputs.

• All clock outputs will be disabled.

• All interrupt status and Interrupt Enable bits will be cleared,

negating the nINT signal.

Upon the later of the internal POR circuit expiring or the nRST input

negating, the device will exit reset and begin self-configuration.

The device will load an initial block of its internal registers using the

configuration stored in the internal One-Time Programmable (OTP)

memory. Once this step is complete, the 8T49N287 will check the

configuration from an external I2C EEPROM at a defined address or

continue loading from OTP. See the section on I2C Boot Initialization

for details on how this is performed.

Once the full configuration has been loaded, the device will respond

to accesses on the serial port and will attempt to lock both PLLs to

the selected sources and begin operation. Once the PLLs are locked,

all the outputs derived from a given PLL will be synchronized and

output phase adjustments can then be applied if desired.

Serial Control Port Description

Serial Control Port Configuration Description

The device has a serial control port capable of responding as a slave

in an I2C compatible configuration, to allow access any of the internal

registers for device programming or examination of internal status. All

registers are configured to have default values. See the specifics for

each register for details.

The device has the additional capability of becoming a master on the

I2C bus only for the purpose of reading its initial register

configurations from a serial EEPROM on the I2C bus. Writing of the

configuration to the serial EEPROM must be performed by another

device on the same I2C bus or pre-programmed into the device prior

to assembly.

I2C Mode Operation

The I2C interface is designed to fully support v1.2 of the I2C

Specification for Normal and Fast mode operation. The device acts

as a slave device on the I2C bus at 100kHz or 400kHz using the

address defined in the Status Interface Control register (0006h), as

modified by the S_A0 input pin setting. The interface accepts

byte-oriented block write and block read operations. Two address

bytes specify the register address of the byte position of the first

sequential order from the lowest to the highest byte (most significant

bit first). Read and write block transfers can be stopped after any

complete byte transfer. During a write operation, data will not be

moved into the registers until the STOP bit is received, at which point,

all data received in the block write will be written simultaneously.

For full electrical I2C compliance, it is recommended to use external

pull-up resistors for SDATA and SCLK. The internal pull-up resistors

have a size of 51k typical.

Figure 3. I2C Slave Read and Write Cycle Sequencing

CurrentRead

SDevAddr+R A Data0 A Data1 A A Datan A P

SequentialRead

SDevAddr+W A Data0 A Data1 A A Datan A POffsetAddrMSB ASr DevAddr+R A

SequentialWrite

SDevAddr+W A Data0 PA Data1 A A Datan A

frommastertoslave

fromslavetomaster

OffsetAddrLSB A

OffsetAddrMSB AOffsetAddrLSB A

S=start

Sr=repeatedstart

A=acknowledge

A=noneacknowledge

P=stop

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 12 REVISION 5 07/09/15

I2C Master Mode

When operating in I2C mode, the 8T49N287 has the capability to

become a bus master on the I2C bus for the purposes of reading its

configuration from an external I2C EEPROM. Only a block read cycle

will be supported.

As an I2C bus master, the 8T49N287 will support the following

functions:

• 7-bit addressing mode

• Base address register for EEPROM

• Validation of the read block via CCITT-8 CRC check against value

stored in last byte (E0h) of EEPROM

• Support for 100kHz and 400kHz operation with speed negotiation.

If bit d0 is set at Byte address 05h in the EEPROM, this will shift

from 100kHz operation to 400kHz operation.

• Support for 1 or 2-byte addressing mode

• Master arbitration with programmable number of retries

• Fixed-period cycle response timer to prevent permanently hanging

the I2C bus.

• Read will abort with an alarm (BOOTFAIL) if any of the following

conditions occur: Slave NACK, Arbitration Fail, Collision during

Address Phase, CRC failure, Slave Response time-out

• The 8T49N287 will not support the following functions:

•I

2C General Call

• Slave clock stretching

•I

2C Start Byte protocol

• EEPROM Chaining

• CBUS compatibility

• Responding to its own slave address when acting as a master

• Writing to external I2C devices including the external EEPROM

used for booting

Figure 4. I2C Master Read Cycle Sequencing

I2C Boot-up Initialization Mode

If enabled (via the BOOT_EEP bit in the Startup register), once the

nRST input has been deasserted (high) and its internal power-up

reset sequence has completed, the device will contend for ownership

of the I2C bus to read its initial register settings from a memory

location on the I2C bus. The address of that memory location is kept

in non-volatile memory in the Startup register. During the boot-up

process, the device will not respond to serial control port accesses.

Once the initialization process is complete, the contents of any of the

device’s registers can be altered. It is the responsibility of the user to

make any desired adjustments in initial values directly in the serial

bus memory.

If a NACK is received to any of the read cycles performed by the

device during the initialization process, or if the CRC does not match

the one stored in address E0h of the EEPROM the process will be

aborted and any uninitialized registers will remain with their default

values. The BOOTFAIL bit (021Eh) in the Global Interrupt Status

If the BOOTFAIL bit is set, then both LOL[n] indicators will be set.

Contents of the EEPROM should be as shown in Table 5 .

SequentialRead(1‐byteoffsetaddress)

SDevAddr+W A Data0 A Data1 A A Datan A PSr DevAddr+R AOffsetAddr A

SequentialRead(2‐byteoffsetaddress)

SDevAddr+W A Data0 A Data1 A A Datan A POffsetAddrMSB ASr DevAddr+R A

OffsetAddrLSB A

frommastertoslave

fromslavetomaster

S=start

Sr=repeatedstart

A=acknowledge

A=noneacknowledge

P=stop

8T49N287 DATA SHEET

REVISION 5 07/09/15 13 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 5. External Serial EEPROM Contents

EEPROM Offset

(Hex)

Contents

D7 D6 D5 D4 D3 D2 D1 D0

00 1111111 1

01 1111111 1

02 1111111 1

03 1111111 1

04 1111111 1

05 1111111

Serial EEPROM

Speed Select

0 = 100kHz

1 = 400kHz

06 1 8T49N287 Device I2C Address [6:2] 0 1

07 0000000 0

08 - DF Desired contents of Device Registers 08h - DFh

E0 Serial EEPROM CRC

E1 - FF Unused

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 14 REVISION 5 07/09/15

Table 6A.Register Blocks

0000 - 0001 Startup Control Registers

0002 - 0005 Device ID Control Registers

0006 - 0007 Serial Interface Control Registers

0008 - 003A Digital PLL0 Control Registers

003B - 006D Digital PLL1 Control Registers

006E - 0076 GPIO Control Registers

0077 - 00AB Output Clock Control Registers

00AC - 00AF Analog PLL0 Control Registers

00B0 - 00B3 Analog PLL1 Control Registers

00B4 - 00B8 Power-Down Control Registers

00B9 - 00C6 Input Monitor Control Registers

00C7 Interrupt Enable Register

00C8 - 00CB Digital Phase Detector Control Registers

00CC - 01FF Reserved1

NOTE 1: Reserved. Always write 0 to this bit location. Read values are not defined.

0200 - 0203 Interrupt Status Registers

0204 Output Phase Adjustment Status Register

0205 - 020E Digital PLL0 Status Registers

020F - 0218 Digital PLL1 Status Registers

0219 General-Purpose Input Status Register

021A - 21F Global Interrupt and Boot Status Register

0220 - 3FF Reserved1

8T49N287 DATA SHEET

REVISION 5 07/09/15 15 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6B. Startup Control Register Bit Field Locations and Descriptions

NOTE 1: These values are specific to the device configuration and can be customized when ordering. Refer to the FemtoClock NG Universal

Frequency Translator Ordering Product Information guide for more details.

Table 6C. Device ID Control Register Bit Field Locations and Descriptions

NOTE 1: These values are specific to the device configuration and can be customized when ordering. Refer to the FemtoClock NG Universal

Frequency Translator Ordering Product Information guide or custom datasheet addendum for more details.

Startup Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

0000 EEP_RTY[4:0] Rsvd nBOOT_OTP nBOOT_EEP

0001 EEP_A15 EEP_ADDR[6:0]

Startup Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

EEP_RTY[4:0] R/W 00001b Select number of times arbitration for the I2C bus to read the serial EEPROM will be

retried before being aborted. Note that this number does not include the original try.

nBOOT_OTP R/W NOTE 1

Internal One-Time Programmable (OTP) memory usage on power-up:

0 = Load power-up configuration from OTP

1 = Only load 1st eight bytes from OTP

nBOOT_EEP R/W NOTE 1

External EEPROM usage on power-up:

0 = Load power-up configuration from external serial EEPROM (overwrites OTP

values)

1 = Don’t use external EEPROM

EEP_A15 R/W NOTE 1 Serial EEPROM supports 15-bit addressing mode (multiple pages).

EEP_ADDR[6:0] R/W NOTE 1 I2C base address for serial EEPROM.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Device ID Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

0002 REV_ID[3:0] DEV_ID[15:12]

0003 DEV_ID[11:4]

0004 DEV_ID[3:0] DASH_CODE [10:7]

0005 DASH_CODE [6:0] 1

Device ID Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

REV_ID[3:0] R/W 0000b Device revision.

DEV_ID[15:0] R/W 605h Device ID code.

DASH CODE [10:0] R/W NOTE 1

Device Dash Code:

Decimal value assigned by IDT to identify the configuration loaded at the factory. 

May be over-written by users at any time. Refer to FemtoClock NG Universal

Frequency Translator Ordering Product Information guide to identify major

configuration parameters associated with this Dash Code value.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 16 REVISION 5 07/09/15

Table 6D. Serial Interface Control Register Bit Field Locations and Descriptions

NOTE 1: These values are specific to the device configuration and can be customized when ordering. Generic dash codes -900 through -908,

-998 and-999 are available and programmed with the default I2C address of 1111100b. Please refer to the FemtoClock NG Universal

Frequency Translator Ordering Product Information guide for more details.

Serial Interface Control Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

0006 Rsvd UFTADD[6:2] UFTADD[1] UFTADD[0]

0007 Rsvd 1

Serial Interface Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

UFTADD[6:2] R/W NOTE 1 Configurable portion of I2C Base Address (bits 6:2) for this device.

UFTADD[1] R/O 0b I2C Base Address bit 1. This bit is fixed at 0.

UFTADD[0] R/O 0b I2C base address bit 0. This address bit reflects the status of the S_A0 external input

pin. See Ta bl e 1 , Pin Description.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

REVISION 5 07/09/15 17 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6E. Digital PLL0 Input Control Register Bit Field Locations and Descriptions

Digital PLL0 Input Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

0008 REFSEL0[2:0] FBSEL0[1:0] RVRT0 SWMODE0

0009 11 10 PRI0_1[1:0] PRI0_0[1:0]

000A 1 1 REFDIS0_1 REFDIS0_0 Rsvd Rsvd STATE0[1:0]

000B Rsvd PRE0_0[20:16]

000C PRE0_0[15:8]

000D PRE0_0[7:0]

000E Rsvd PRE0_1[20:16]

000F PRE0_1[15:8]

0010 PRE0_1[7:0]

0011 Rsvd Rsvd

0012 Rsvd

0013 Rsvd

0014 Rsvd Rsvd

0015 Rsvd

0016 Rsvd

Digital PLL0 Input Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

REFSEL0[2:0] R/W 000b

Input reference selection for Digital PLL0:

000 = Automatic selection

001 = Manual selection by GPIO inputs

010 through 011 = Reserved

100 = Force selection of Input Reference 0

101 = Force selection of Input Reference 1

110 = Do not use

111 = Do not use

FBSEL0[2:0] R/W 000b

Feedback mode selection for Digital PLL0:

000 through 011 = internal feedback divider

100 = external feedback from Input Reference 0

101 = external feedback from Input Reference 1

110 = do not use

111 = do not use

RVRT0 R/W 1b

Automatic switching mode for Digital PLL0:

0 = non-revertive switching

1 = revertive switching

SWMODE0 R/W 1b

Controls how Digital PLL0 adjusts output phase when switching between input references:

0 = Absorb any phase differences between old and new input references at the PLL output.

Recommended for use when both input references are in the same clock domain.

1 = Limit the maximum rate of phase change at the PLL output when adjusting to a new

input reference’s phase/frequency using phase-slope limiting as set in the SLEWn bits.

Recommended for use when the input references are not in the same clock domain.

PRI0_0[1:0] R/W 00b

Switchover priority for Input Reference 0 when used by Digital PLL0:

00 = 1st priority

01 = 2nd priority

10 = do not use

11 = do not use

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 18 REVISION 5 07/09/15

PRI0_1[1:0] R/W 01b

Switchover priority for Input Reference 1 when used by Digital PLL0:

00 = 1st priority

01 = 2nd priority

10 = do not use

11 = do not use

REFDIS0_0 R/W 0b

Input Reference 0 Switching Selection Disable for Digital PLL0:

0 = Input Reference 0 is included in the switchover sequence for Digital PLL0

1 = Input Reference 0 is not included in the switchover sequence for Digital PLL0

REFDIS0_1 R/W 0b

Input Reference 1 Switching Selection Disable for Digital PLL0:

0 = Input Reference 1 is included in the switchover sequence for Digital PLL0

1 = Input Reference 1 is not included in the switchover sequence for Digital PLL0

STATE0[1:0] R/W 00b

Digital PLL0 State Machine Control:

00 = Run automatically

01 = Force FREERUN state - set this if in Synthesizer Mode for PLL0

10 = Force NORMAL state

11 = Force HOLDOVER state

PRE0_0[20:0] R/W 000000h Pre-divider ratio for Input Reference 0 when used by Digital PLL0.

PRE0_1[20:0] R/W 000000h Pre-divider ratio for Input Reference 1 when used by Digital PLL0.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Digital PLL0 Input Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

8T49N287 DATA SHEET

REVISION 5 07/09/15 19 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6F. Digital PLL0 Feedback Control Register Bit Field Locations and Descriptions

Digital PLL0 Feedback Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1 D0

0017 M1_0_0[23:16]

0018 M1_0_0[15:8]

0019 M1_0_0[7:0]

001A M1_0_1[23:16]

001B M1_0_1[15:8]

001C M1_0_1[7:0]

001D Rsvd

001E Rsvd

001F Rsvd

0020 Rsvd

0021 Rsvd

0022 Rsvd

0023 LCKBW0[3:0] ACQBW0[3:0]

0024 LCKDAMP0[2:0] ACQDAMP0[2:0] PLLGAIN0[1:0]

0025 Rsvd Rsvd Rsvd Rsvd

0026 Rsvd

0027 Rsvd

0028 Rsvd Rsvd

0029 Rsvd

002A Rsvd

002B FFh

002C FFh

002D FFh

002E FFh

002F SLEW0[1:0] Rsvd HOLD0[1:0] Rsvd HOLDAVG0 FASTLCK0

0030 LOCK0[7:0]

0031 Rsvd DSM_INT0[8]

0032 DSM_INT0[7:0]

0033 Rsvd DSMFRAC0[20:16]

0034 DSMFRAC0[15:8]

0035 DSMFRAC0[7:0]

0036 Rsvd

0037 01h

0038 Rsvd

0039 Rsvd

003A DSM_ORD0[1:0] DCXOGAIN0[1:0] Rsvd DITHGAIN0[2:0]

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 20 REVISION 5 07/09/15

Digital PLL0 Feedback Configuration Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

M1_0_0[23:0] R/W 070000h M1 Feedback divider ratio for Input Reference 0 when used by Digital PLL0.

M1_0_1[23:0] R/W 070000h M1 Feedback divider ratio for Input Reference 1 when used by Digital PLL0.

LCKBW0[3:0] R/W 0111b

Digital PLL Loop Bandwidth while locked:

0000 = Reserved

0001 = Reserved

0010 = Reserved

0011 = 1.40625Hz

0100 = 2.8125Hz

0101 = 5.625Hz

0110 = 11.25Hz

0111 = 22.5Hz

1000 = 45Hz

1001 = 90Hz

1010 = 180Hz

1011 = 360Hz

1100 through 1111 = Reserved

ACQBW0[3:0] R/W 0111b

Digital PLL0 Loop Bandwidth while in acquisition (not-locked):

0000 = Reserved

0001 = Reserved

0010 = Reserved

0011 = 1.40625Hz

0100 = 2.8125Hz

0101 = 5.625Hz

0110 = 11.25Hz

0111 = 22.5Hz

1000 = 45Hz

1001 = 90Hz

1010 = 180Hz

1011 = 360Hz

1100 through 1111 = Reserved

LCKDAMP0[2:0] R/W 011b

Damping factor for Digital PLL0 while locked:

000 = Reserved

001 = 1

010 = 2

011 = 5

100 = 10

101 = 20

110 = Reserved

111 = Reserved

ACQDAMP0[2:0] R/W 011b

Damping factor for Digital PLL0 while in acquisition (not locked):

000 = Reserved

001 = 1

010 = 2

011 = 5

100 = 10

101 = 20

110 = Reserved

111 = Reserved

PLLGAIN0[1:0] R/W 01b

Digital Loop Filter Gain Settings for Digital PLL0:

00 = 0.5

01 = 1

10 = 1.5

11 = 2

8T49N287 DATA SHEET

REVISION 5 07/09/15 21 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

NOTE 1: Settings other than “00” may result in a significant increase in initial lock time.

SLEW0[1:0] R/W 00b

Phase-slope control for Digital PLL0:

00 = no limit - controlled by loop bandwidth of Digital PLL0 (NOTE 1)

01 = 83 µsec/sec

10 = 13 µsec/sec

11 = Reserved

HOLD0[1:0] R/W 00b

Holdover Averaging mode selection for Digital PLL0:

00 = Instantaneous mode - uses historical value 100ms prior to entering holdover

01 = Fast Average Mode

10 = Reserved

11 = Set VCO control voltage to VCC/2

HOLDAVG0 R/W 0b

Holdover Averaging Enable for Digital PLL0:

0 = Holdover averaging disabled

1 = Holdover averaging enabled as defined in HOLD0[1:0]

FASTLCK0 R/W 0b

Enables Fast Lock operation for Digital PLL0:

0 = Normal locking using LCKBW0 & LCKDAMP0 fields in all cases

1 = Fast Lock mode using ACQBW0 & ACQDAMP0 when not phase locked and

LCKBW0 & LCKDAMP0 once phase locked

LOCK0[7:0] R/W 3Fh Lock window size for Digital PLL0. Unsigned 2’s complement binary number in steps

of 2.5ns, giving a total range of 640ns. Do not program to 0.

DSM_INT0[8:0] R/W 02Dh

Integer portion of the Delta-Sigma Modulator value. Do not set higher than FFh. This

implies that for crystal frequencies lower than 16MHz, the doubler circuit must be

enabled.

DSMFRAC0[20:0] R/W 000000h Fractional portion of Delta-Sigma Modulator value. Divide this number by 221 to

determine the actual fraction.

DSM_ORD0[1:0] R/W 11b

Delta-Sigma Modulator Order for Digital PLL0:

00 = Delta-Sigma Modulator disabled

01 = 1st order modulation

10 = 2nd order modulation

11 = 3rd order modulation

DCXOGAIN0[1:0] R/W 01b

Multiplier applied to instantaneous frequency error before it is applied to the Digitally

Controlled Oscillator in Digital PLL0:

00 = 0.5

01 = 1

10 = 2

11 = 4

DITHGAIN0[2:0] R/W 000b

Dither Gain setting for Digital PLL0:

000 = no dither

001 = Least Significant Bit (LSB) only

010 = 2 LSBs

011 = 4 LSBs

100 = 8 LSBs

101 = 16 LSBs

110 = 32 LSBs

111 = 64 LSBs

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Digital PLL0 Feedback Configuration Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 22 REVISION 5 07/09/15

Table 6G. Digital PLL1 Input Control Register Bit Field Locations and Descriptions

Digital PLL1 Input Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

003B REFSEL1[2:0] FBSEL1[1:0] RVRT1 SWMODE1

003C 11 10 PRI1_1[1:0] PRI1_0[1:0]

003D 1 1 REFDIS1_1 REFDIS1_0 Rsvd Rsvd STATE1[1:0]

003E Rsvd PRE1_0[20:16]

003F PRE1_0[15:8]

0040 PRE1_0[7:0]

0041 Rsvd PRE1_1[20:16]

0042 PRE1_1[15:8]

0043 PRE1_1[7:0]

0044 Rsvd Rsvd

0045 Rsvd

0046 Rsvd

0047 Rsvd Rsvd

0048 Rsvd

0049 Rsvd

Digital PLL1 Input Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

REFSEL1[2:0] R/W 000b

Input reference selection for Digital PLL1:

000 = Automatic selection

001 = Manual selection by GPIO inputs

010 through 011 = Reserved

100 = Force selection of Input Reference 0

101 = Force selection of Input Reference 1

110 = do not use

111 = do not use

FBSEL1[2:0] R/W 000b

Feedback mode selection for Digital PLL1:

000 through 011 = internal feedback divider

100 = external feedback from Input Reference 0

101 = external feedback from Input Reference 1

110 = do not use

111 = do not use

RVRT1 R/W 1b

Automatic switching mode for Digital PLL1:

0 = non-revertive switching

1 = revertive switching

SWMODE1 R/W 1b

Controls how Digital PLL1 adjusts output phase when switching between input references:

0 = Absorb any phase differences between old and new input references at the PLL output.

Recommended for use when both input references are in the same clock domain.

1 = Limit the maximum rate of phase change at the PLL output when adjusting to a new

input reference’s phase/frequency using phase-slope limiting as set in the SLEWn bits.

Recommended for use when the input references are not in the same clock domain.

PRI1_0[1:0] R/W 00b

Switchover priority for Input Reference 0 when used by Digital PLL1:

00 = 1st priority

01 = 2nd priority

10 = do not use

11 = do not use

8T49N287 DATA SHEET

REVISION 5 07/09/15 23 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

PRI1_1[1:0] R/W 01b

Switchover priority for Input Reference 1 when used by Digital PLL1:

00 = 1st priority

01 = 2nd priority

10 = do not use

11 = do not use

REFDIS1_0 R/W 0b

Input Reference 0 Switching Selection Disable for Digital PLL1:

0 = Input Reference 0 is included in the switchover sequence for Digital PLL1

1 = Input Reference 0 is not included in the switchover sequence for Digital PLL1

REFDIS1_1 R/W 0b

Input Reference 1 Switching Selection Disable for Digital PLL1:

0 = Input Reference 1 is included in the switchover sequence for Digital PLL1

1 = Input Reference 1 is not included in the switchover sequence for Digital PLL1

STATE1[1:0] R/W 00b

Digital PLL1 State Machine Control:

00 = Run automatically

01 = Force FREERUN state - set this if in Synthesizer Mode for PLL1

10 = Force NORMAL state

11 = Force HOLDOVER state

PRE1_0[20:0] R/W 000000h Pre-divider ratio for Input Reference 0 when used by Digital PLL1.

PRE1_1[20:0] R/W 000000h Pre-divider ratio for Input Reference 1 when used by Digital PLL1.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Digital PLL1 Input Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 24 REVISION 5 07/09/15

Table 6H. Digital PLL1 Feedback Control Register Bit Field Locations and Descriptions

Digital PLL1 Feedback Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

004A M1_1_0[23:16]

004B M1_1_0[15:8]

004C M1_1_0[7:0]

004D M1_1_1[23:16]

004E M1_1_1[15:8]

004F M1_1_1[7:0]

0050 Rsvd

0051 Rsvd

0052 Rsvd

0053 Rsvd

0054 Rsvd

0055 Rsvd

0056 LCKBW1[3:0] ACQBW1[3:0]

0057 LCKDAMP1[2:0] ACQDAMP1[2:0] PLLGAIN1[1:0]

0058 Rsvd Rsvd Rsvd Rsvd

0059 Rsvd

005A Rsvd

005B Rsvd Rsvd

005C Rsvd

005D Rsvd

005E FFh

005F FFh

0060 FFh

0061 FFh

0062 SLEW1[1:0] Rsvd HOLD1[1:0] Rsvd HOLDAVG1 FASTLCK1

0063 LOCK1[7:0]

0064 Rsvd DSM_INT1[8]

0065 DSM_INT1[7:0]

0066 Rsvd DSMFRAC1[20:16]

0067 DSMFRAC1[15:8]

0068 DSMFRAC1[7:0]

0069 Rsvd

006A 01h

006B Rsvd

006C Rsvd

006D DSM_ORD1[1:0] DCXOGAIN1[1:0] Rsvd DITHGAIN1[2:0]

8T49N287 DATA SHEET

REVISION 5 07/09/15 25 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Digital PLL1 Feedback Configuration Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

M1_1_0[23:0] R/W 070000h M1 Feedback divider ratio for Input Reference 0 when used by Digital PLL1.

M1_1_1[23:0] R/W 070000h M1 Feedback divider ratio for Input Reference 1 when used by Digital PLL1.

LCKBW1[3:0] R/W 0111b

Digital PLL1 Loop Bandwidth while locked:

0000 = Reserved

0001 = Reserved

0010 = Reserved

0011 = 1.40625Hz

0100 = 2.8125Hz

0101 = 5.625Hz

0110 = 11.25Hz

0111 = 22.5Hz

1000 = 45Hz

1001 = 90Hz

1010 = 180Hz

1011 = 360Hz

1100 through 1111 = Reserved

ACQBW1[3:0] R/W 0111b

Digital PLL1 Loop Bandwidth while in acquisition (not-locked):

0000 = Reserved

0001 = Reserved

0010 = Reserved

0011 = 1.40625Hz

0100 = 2.8125Hz

0101 = 5.625Hz

0110 = 11.25Hz

0111 = 22.5Hz

1000 = 45Hz

1001 = 90Hz

1010 = 180Hz

1011 = 360Hz

1100 through 1111 = Reserved

LCKDAMP1[2:0] R/W 011b

Damping factor for Digital PLL1 while locked:

000 = Reserved

001 = 1

010 = 2

011 = 5

100 = 10

101 = 20

110 = Reserved

111 = Reserved

ACQDAMP1[2:0] R/W 011b

Damping factor for Digital PLL1 while in acquisition (not locked):

000 = Reserved

001 = 1

010 = 2

011 = 5

100 = 10

101 = 20

110 = Reserved

111 = Reserved

PLLGAIN1[1:0] R/W 01b

Digital Loop Filter Gain Settings for Digital PLL1:

00 = 0.5

01 = 1

10 = 1.5

11 = 2

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 26 REVISION 5 07/09/15

NOTE 1: Settings other than “00” may result in a significant increase in initial lock time.

SLEW1[1:0] R/W 00b

Phase-slope control for Digital PLL1:

00 = no limit - controlled by loop bandwidth of Digital PLL0 (NOTE 1)

01 = 83 µsec/sec

10 = 13 µsec/sec

11 = Reserved

HOLD1[1:0] R/W 00b

Holdover Averaging mode selection for Digital PLL1:

00 = Instantaneous mode - uses historical value 100ms prior to entering holdover

01 = Fast Average Mode

10 = Reserved

11 = Set VCO control voltage to VCC/2

HOLDAVG1 R/W 0b

Holdover Averaging Enable for Digital PLL1:

0 = Holdover averaging disabled

1 = Holdover averaging enabled as defined in HOLD1[1:0]

FASTLCK1 R/W 0b

Enables Fast Lock operation for Digital PLL1:

0 = Normal locking using LCKBW1 & LCKDAMP1 fields in all cases

1 = Fast Lock mode using ACQBW1 & ACQDAMP1 when not phase locked and

LCKBW1 & LCKDAMP1 once phase locked

LOCK1[7:0] R/W 3Fh Lock window size for Digital PLL1. Unsigned 2’s complement binary number in steps of

2.5ns, giving a total range of 640ns. Do not program to 0.

DSM_INT1[8:0] R/W 02Dh

Integer portion of the Delta-Sigma Modulator value. Do not set higher than FFh. This

implies that for crystal frequencies lower than 16MHz, the doubler circuit must be

enabled.

DSMFRAC1[20:0] R/W 000000h Fractional portion of Delta-Sigma Modulator value. Divide this number by 221 to

determine the actual fraction.

DSM_ORD1[1:0] R/W 11b

Delta-Sigma Modulator Order for Digital PLL1:

00 = Delta-Sigma Modulator disabled

01 = 1st order modulation

10 = 2nd order modulation

11 = 3rd order modulation

DCXOGAIN1[1:0] R/W 01b

Multiplier applied to instantaneous frequency error before it is applied to the Digitally

Controlled Oscillator in Digital PLL1:

00 = 0.5

01 = 1

10 = 2

11 = 4

DITHGAIN1[2:0] R/W 000b

Dither Gain setting for Digital PLL1:

000 = no dither

001 = Least Significant Bit (LSB) only

010 = 2 LSBs

011 = 4 LSBs

100 = 8 LSBs

101 = 16 LSBs

110 = 32 LSBs

111 = 64 LSBs

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Digital PLL1 Feedback Configuration Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

REVISION 5 07/09/15 27 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6I. GPIO Control Register Bit Field Locations and Descriptions

The values observed on any GPIO pins that are used as general purpose inputs are visible in the GPI[3:0] register that is located at location

0219h near a number of other read-only registers.

006E Rsvd GPIO_DIR[3:0]

006F Rsvd GPI3SEL[2] GPI2SEL[2] GPI1SEL[2] GPI0SEL[2]

0070 Rsvd GPI3SEL[1] GPI2SEL[1] GPI1SEL[1] GPI0SEL[1]

0071 Rsvd GPI3SEL[0] GPI2SEL[0] GPI1SEL[0] GPI0SEL[0]

0072 Rsvd GPO3SEL[2] GPO2SEL[2] GPO1SEL[2] GPO0SEL[2]

0073 Rsvd GPO3SEL[1] GPO2SEL[1] GPO1SEL[1] GPO0SEL[1]

0074 Rsvd GPO3SEL[0] GPO2SEL[0] GPO1SEL[0] GPO0SEL[0]

0075 Rsvd

0076 Rsvd GPO[3:0]

GPIO Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

GPIO Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

GPIO_DIR[3:0] R/W 00h

Direction control for General-Purpose I/O Pins GPIO[3:0]:

0 = input mode

1 = output mode

GPI0SEL[2:0] R/W 000b

Function of GPIO[0] pin when set to input mode by GPIO_DIR[0] register bit:

000 = General Purpose Input (value on GPIO[0] pin directly reflected in GPI[0] register bit)

001 = Output Enable control for output Q0

010 = Output Enable control for output Q4

011 = reserved

100 through 111 = reserved

GPI1SEL[2:0] R/W 000b

Function of GPIO[1] pin when set to input mode by GPIO_DIR[1] register bit:

000 = General Purpose Input (value on GPIO[1] pin directly reflected in GPI[1] register bit)

001 = Output Enable control for output Q1

010 = Output Enable control for output Q5

011 through 111 = reserved

GPI2SEL[2:0] R/W 000b

Function of GPIO[2] pin when set to input mode by GPIO_DIR[2] register bit:

000 = General Purpose Input (value on GPIO[2] pin directly reflected in GPI[2] register bit)

001 = Output Enable control for output Q2

010 = Output Enable control for output Q6

011 = reserved

100 = reserved

101 = CSEL0: Manual Clock Select Input for PLL0

110 through 111 = reserved

GPI3SEL[2:0] R/W 000b

Function of GPIO[3] pin when set to input mode by GPIO_DIR[3] register bit:

000 = General Purpose Input (value on GPIO[3] pin directly reflected in GPI[3] register bit)

001 = Output Enable control for output Q3

010 = Output Enable control for output Q7

011 = reserved

101 = CSEL1: Manual Clock Select Input for PLL1

100, 110, 111 = reserved

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 28 REVISION 5 07/09/15

GPO0SEL[2:0] R/W 000b

Function of GPIO[0] pin when set to output mode by GPIO_DIR[0] register bit:

000 = General Purpose Output (value in GPO[0] register bit driven on GPIO[0] pin

001 = Loss-of-Lock Status Flag for Digital PLL0 reflected on GPIO[0] pin

010 = Loss-of-Lock Status Flag for Digital PLL1 reflected on GPIO[0] pin

011 = reserved

100 = reserved

101 = reserved

110 through 111 = reserved

GPO1SEL[2:0] R/W 000b

Function of GPIO[1] pin when set to output mode by GPIO_DIR[1] register bit:

000 = General Purpose Output (value in GPO[1] register bit driven on GPIO[1] pin

001 = Holdover Status Flag for Digital PLL0 reflected on GPIO[1] pin

010 = Holdover Status Flag for Digital PLL1 reflected on GPIO[1] pin

011 = reserved

100 = reserved

101 = reserved

110 = reserved

111 = reserved

GPO2SEL[2:0] R/W 000b

Function of GPIO[2] pin when set to output mode by GPIO_DIR[2] register bit:

000 = General Purpose Output (value in GPO[2] register bit driven on GPIO[2] pin

001 = Loss-of-Signal Flag for Input Reference 0 reflected on GPIO[2] pin

010 = Loss-of-Signal Flag for Input Reference 1 reflected on GPIO[2] pin

011 = reserved

100 = reserved

101 through 111 = reserved

GPO3SEL[2:0] R/W 000b

Function of GPIO[3] pin when set to output mode by GPIO_DIR[3] register bit:

000 = General Purpose Output (value in GPO[3] register bit driven on GPIO[3] pin

001 = Loss-of-Lock Status Flag for Digital PLL1 reflected on GPIO[3] pin

010 = Loss-of-Signal Status Flag for Input Reference 1 reflected on GPIO[3] pin

011 = reserved

100 = reserved

101 through 111 = reserved

GPO[3:0] R/W 00h Output Values reflect on pin GPIO[3:0] when General-Purpose Output Mode selected.

Rsvd R/W -Reserved. Always write 0 to this bit location. Read values are not defined.

GPIO Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

8T49N287 DATA SHEET

REVISION 5 07/09/15 29 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6J. Output Driver Control Register Bit Field Locations and Descriptions

Output Driver Control Register Block Field Locations

Address (Hex)D7D6D5 D4 D3D2D1 D0

0077 OUTEN[7:0]

0078 POL_Q[7:0]

0079 OUTMODE7[2:0] SE_MODE7 OUTMODE6[2:0] SE_MODE6

007A OUTMODE5[2:0] SE_MODE5 OUTMODE4[2:0] SE_MODE4

007B OUTMODE3[2:0] SE_MODE3 OUTMODE2[2:0] SE_MODE2

007C OUTMODE1[2:0] SE_MODE1 OUTMODE0[2:0] SE_MODE0

Output Driver Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

OUTEN[7:0] R/W 00h

Output Enable control for Clock Outputs Q[7:0], nQ[7:0]:

0 = Qn is in a high-impedance state

1 = Qn is enabled as indicated in appropriate OUTMODEn[2:0] register field

POL_Q[7:0] R/W 00h

Polarity of Clock Outputs Q[7:0], nQ[7:0]:

0 = normal polarity

1 = inverted polarity

OUTMODEm[2:0] R/W 001b

Output Driver Mode of Operation for Clock Output Pair Qm, nQm:

000 = High-impedance

001 = LVPECL

010 = LVDS

011 = LVCMOS

100 = HCSL

101 - 111 = reserved

SE_MODEm R/W 0b

Behavior of Output Pair Qm, nQm when LVCMOS operation is selected:

(Must be 0 if LVDS, HCSL or LVPECL output style is selected)

0 = Qm and nQm are both the same frequency but inverted in phase

1 = Qm and nQm are both the same frequency and phase

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 30 REVISION 5 07/09/15

Table 6K. Output Divider Control Register Bit Field Locations and Descriptions

Output Divider Control Register Block Field Locations

Address (Hex)D7 D6 D5D4D3D2D1D0

007D Rsvd NS1_Q0[1:0]

007E NS2_Q0[15:8]

007F NS2_Q0[7:0]

0080 Rsvd NS1_Q1[1:0]

0081 NS2_Q1[15:8]

0082 NS2_Q1[7:0]

0083 Rsvd N_Q2[17:16]

0084 N_Q2[15:8]

0085 N_Q2[7:0]

0086 Rsvd N_Q3[17:16]

0087 N_Q3[15:8]

0088 N_Q3[7:0]

0089 Rsvd NS1_Q4[1:0]

008A NS2_Q4[15:8]

008B NS2_Q4[7:0]

008C Rsvd NS1_Q5[1:0]

008D NS2_Q5[15:8]

008E NS2_Q5[7:0]

008F Rsvd NS1_Q6[1:0]

0090 NS2_Q6[15:8]

0091 NS2_Q6[7:0]

0092 Rsvd NS1_Q7[1:0]

0093 NS2_Q7[15:8]

0094 NS2_Q7[7:0]

0095 Rsvd NFRAC_Q2[27:24]

0096 NFRAC_Q2[23:16]

0097 NFRAC_Q2[15:8]

0098 NFRAC_Q2[7:0]

0099 Rsvd NFRAC_Q3[27:24]

009A NFRAC_Q3[23:16]

009B NFRAC_Q3[15:8]

009C NFRAC_Q3[7:0]

8T49N287 DATA SHEET

REVISION 5 07/09/15 31 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Output Divider Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

NS1_Qm[1:0]

(m = 0, 1) R/W 10b

1st Stage Output Divider Ratio for Output Clock Qm, nQm: (m = 0, 1):

00 = /5

01 = /6

10 = /4

11 = Output Qm, nQm not switching

NS1_Qm[1:0]

(m = 4, 5, 6, 7) R/W 10b

1st Stage Output Divider Ratio for Output Clock Qm, nQm (m = 4, 5, 6, 7):

00 = /5

01 = /6

10 = /4

11 = /1 (Do not use this selection if PLL0 or PLL1 are the source since the 2nd-stage

divider has a limit of 1GHz.)

NS2_Qm[15:0] R/W 0002h

2nd Stage Output Divider Ratio for Output Clock Qm, nQm (m = 0, 1, 4, 5, 6, 7):

Actual divider ratio is 2x the value written here.

A value of 0 in this register will bypass the second stage of the divider.

N_Qm[17:0] R/W 00008h

Integer Portion of Output Divider Ratio for Output Clock Qm, nQm (m = 2, 3):

Values of 0, 1 or 2 cannot be written to this register.

Actual divider ratio is 2x the value written here.

NFRAC_Qm[27:0] R/W 0000000h

Fractional Portion of Output Divider Ratio for Output Clock Qm, nQm (m = 2, 3):

Actual fractional portion is 2x the value written here.

Fraction = (NFRAC_Qm * 2) * 2-28

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 32 REVISION 5 07/09/15

Table 6L. Output Clock Phase Adjustment Control Register Bit Field Locations and Descriptions

Output Clock Phase Adjustment Control Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

009D CRSE_TRG[7:0]

009E Rsvd COARSE0[4:0]

009F Rsvd COARSE1[4:0]

00A0 Rsvd COARSE2[4:0]

00A1 Rsvd COARSE3[4:0]

00A2 Rsvd COARSE4[4:0]

00A3 Rsvd COARSE5[4:0]

00A4 Rsvd COARSE6[4:0]

00A5 Rsvd COARSE7[4:0]

00A6 Rsvd FINE2[3:0]

00A7 Rsvd FINE3[3:0]

Output Clock Phase Adjustment Control Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

CRSE_TRG[7:0] R/W 00h

Trigger Coarse Phase Adjustment for output Qm, nQm by amount specified in

COARSEm[4:0] register upon 01 transition of this Trigger register bit. Please ensure the

PA_BUSYm status bit is 0 before triggering another adjustment cycle on that particular

output. Trigger bit must be returned to 0 before another delay cycle can be triggered.

COARSEm[4:0] R/W 00000b Number of periods to be inserted when Trigger happens. Relevant clock period is

determined by the clock source selected for output Qm, nQm in its CLK_SELm register field.

FINEm[3:0] R/W 0000b

Number of 1/16ths of the relevant clock period to add to the phase of output Qm, nQm (m =

2,3). Relevant clock period is determined by the clock source selected for output Qm, nQm

in its CLK_SELm register field. The PLLn_SYN bit for the PLL driving the output divider for

the output in question must be toggled to make this value take effect. Note that toggling the

PLLn_SYN bit will clear all Coarse delay values and so Fine delay should be set first.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

REVISION 5 07/09/15 33 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6M. Output Clock Source Control Register Bit Field Locations and Descriptions

Output Clock Source Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

00A8 Rsvd PLL1_SYN PLL0_SYN CLK_SEL3 CLK_SEL2 CLK_SEL1 CLK_SEL0

00A9 Rsvd CLK_SEL5[2:0] Rsvd CLK_SEL4[2:0]

00AA Rsvd CLK_SEL7[2:0] Rsvd CLK_SEL6[2:0]

00AB 11 11 Rsvd Rsvd

Output Clock Source Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

PLL1_SYN R/W 0b

Output Synchronization Control for Outputs Derived from PLL1:

Setting this bit from 01 will cause the output divider(s) for the affected outputs to be

held in reset.

Setting this bit from 10 will release all the output divider(s) for the affected outputs to

run from the same point in time with the coarse output phase adjustment reset to 0.

PLL0_SYN R/W 0b

Output Synchronization Control for Outputs Derived from PLL0:

Setting this bit from 01 will cause the output divider(s) for the affected outputs to be

held in reset.

Setting this bit from 10 will release all the output divider(s) for the affected outputs to

run from the same point in time with the coarse output phase adjustment reset to 0.

CLK_SEL0 R/W 0b

Clock Source Selection for output Q0, nQ0:

0 = PLL0

1 = PLL1

CLK_SEL1 R/W 1b

Clock Source Selection for output Q1, nQ1:

0 = PLL0

1 = PLL1

CLK_SEL2 R/W 0b

Clock Source Selection for output Q2, nQ2:

0 = PLL0

1 = PLL1

CLK_SEL3 R/W 1b

Clock Source Selection for output Q3, nQ3:

0 = PLL0

1 = PLL1

CLK_SEL4[2:0] R/W 000b

Clock Source Selection for output Q4, nQ4: Do not select Input Reference 0 or 1 if that

input is faster than 250MHz:

000 = PLL0

001 = PLL1

010 = Output Q2, nQ2

011 = Output Q3, nQ3

100 = Input Reference 0 (CLK0)

101 = Input Reference 1 (CLK1)

110 = Reserved

111 = Crystal input

CLK_SEL5[2:0] R/W 010b

Clock Source Selection for output Q5, nQ5: Do not select Input Reference 0 or 1 if that

input is faster than 250MHz:

000 = PLL0

001 = PLL1

010 = Output Q2, nQ2

011 = Output Q3, nQ3

100 = Input Reference 0 (CLK0)

101 = Input Reference 1 (CLK1)

110 = Reserved

111 = Crystal input

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 34 REVISION 5 07/09/15

CLK_SEL6[2:0] R/W 000b

Clock Source Selection for output Q6, nQ6: Do not select Input Reference 0 or 1 if that

input is faster than 250MHz:

000 = PLL0

001 = PLL1

010 = Output Q2, nQ2

011 = Output Q3, nQ3

100 = Input Reference 0 (CLK0)

101 = Input Reference 1 (CLK1)

110 = Reserved

111 = Crystal input

CLK_SEL7[2:0] R/W 101b

Clock Source Selection for output Q7, nQ7: Do not select Input Reference 0 or 1 if that

input is faster than 250MHz:

000 = PLL0

001 = PLL1

010 = Output Q2, nQ2

011 = Output Q3 nQ3

100 = Input Reference 0 (CLK0)

101 = Input Reference 1 (CLK1)

110 = Reserved

111 = Crystal input

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Output Clock Source Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

REVISION 5 07/09/15 35 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6N. Analog PLL0 Control Register Bit Field Locations and Descriptions

Please contact IDT through one of the methods listed on the last page of this datasheet for details on how to set these fields for a particular

user configuration.

00AC CPSET_0[2:0] RS_0[1:0] CP_0[1:0] WPOST_0

00AD Rsvd SYN_MODE0 Rsvd DLCNT_0 DBITM_0

00AE Rsvd VCOMAN_0 DBIT1_0[4:0]

00AF Rsvd DBIT2_0[4:0]

CPSET_0[2:0] R/W 100b

Charge Pump Current Setting for Analog PLL0:

000 = 110µA

001 = 220µA

010 = 330µA

011 = 440µA

100 = 550µA

101 = 660µA

110 = 770µA

111 = 880µA

RS_0[1:0] R/W 01b

Internal Loop Filter Series Resistor Setting for Analog PLL0:

00 = 330

01 = 640

10 = 1.2k

11 = 1.79k

CP_0[1:0] R/W 01b

Internal Loop Filter Parallel Capacitor Setting for Analog PLL0:

00 = 40pF

01 = 80pF

10 = 140pF

11 = 200pF

WPOST_0 R/W 1b

Internal Loop Filter 2nd-Pole Setting for Analog PLL0:

0 = Rpost = 497, Cpost = 40pF

1 = Rpost = 1.58k, Cpost = 40pF

DLCNT_0 R/W 1b

Digital Lock Count Setting for Analog PLL0:

Value should be set to 0 (1ppm accuracy) if external capacitor value is >95nF,

otherwise set to 1.

0 = 1ppm accuracy

1 = 16ppm accuracy

DBITM_0 R/W 0b

Digital Lock Manual Override Setting for Analog PLL0:

0 = Automatic Mode

1 = Manual Mode

VCOMAN_0 R/W 1b

Manual Lock Mode VCO Selection Setting for Analog PLL0:

0 = VCO2

1 = VCO1

DBIT1_0[4:0] R/W 01011b Manual Mode Digital Lock Control Setting for VCO1 in Analog PLL0.

DBIT2_0[4:0] R/W 00000b Manual Mode Digital Lock Control Setting for VCO2 in Analog PLL0.

SYN_MODE0 R/W 0b

Frequency Synthesizer Mode Control for PLL0:

0 = PLL0 jitter attenuates and translates one or more input references

1 = PLL0 synthesizes output frequencies using only the crystal as a reference

Note that the STATE0[1:0] field in the Digital PLL0 Control Register must be set to

Force Freerun state.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Analog PLL0 Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

Analog PLL0 Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 36 REVISION 5 07/09/15

Table 6O. Analog PLL1 Control Register Bit Field Locations and Descriptions

Please contact IDT through one of the methods listed on the last page of this datasheet for details on how to set these fields for a particular

user configuration.

00B0 CPSET_1[2:0] RS_1[1:0] CP_1[1:0] WPOST_1

00B1 Rsvd SYN_MODE1 Rsvd DLCNT_1 DBITM_1

00B2 Rsvd VCOMAN_1 DBIT1_1[4:0]

00B3 Rsvd DBIT2_1[4:0]

CPSET_1[2:0] R/W 100b

Charge Pump Current Setting for Analog PLL1:

000 = 110µA

001 = 220µA

010 = 330µA

011 = 440µA

100 = 550µA

101 = 660µA

110 = 770µA

111 = 880µA

RS_1[1:0] R/W 01b

Internal Loop Filter Series Resistor Setting for Analog PLL1:

00 = 330

01 = 640

10 = 1.2k

11 = 1.79k

CP_1[1:0] R/W 01b

Internal Loop Filter Parallel Capacitor Setting for Analog PLL1:

00 = 40pF

01 = 80pF

10 = 140pF

11 = 200pF

WPOST_1 R/W 1b

Internal Loop Filter 2nd-Pole Setting for Analog PLL1:

0 = Rpost = 497, Cpost = 40pF

1 = Rpost = 1.58k, Cpost = 40pF

DLCNT_1 R/W 1b

Digital Lock Count Setting for Analog PLL1:

Value should be set to 0 (1ppm accuracy) if external capacitor value is >95nF,

otherwise set to 1.

0 = 1ppm accuracy

1 = 16ppm accuracy

DBITM_1 R/W 0b

Digital Lock Manual Override Setting for Analog PLL1:

0 = Automatic Mode

1 = Manual Mode

VCOMAN_1 R/W 1b

Manual Lock Mode VCO Selection Setting for Analog PLL1:

0 = VCO2

1 = VCO1

DBIT1_1[4:0] R/W 01011b Manual Mode Digital Lock Control Setting for VCO1 in Analog PLL1.

DBIT2_1[4:0] R/W 00000b Manual Mode Digital Lock Control Setting for VCO2 in Analog PLL1.

SYN_MODE1 R/W 0b

Frequency Synthesizer Mode Control for PLL1:

0 = PLL1 jitter attenuates and translates one or more input references

1 = PLL1 synthesizes output frequencies using only the crystal as a reference

Note that the STATE1[1:0] field in the Digital PLL1 Control Register must be set to

Force Freerun state.

Rsvd R/W -Reserved. Always write 0 to this bit location. Read values are not defined.

Analog PLL1 Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

Analog PLL1 Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

REVISION 5 07/09/15 37 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6P. Power Down Control Register Bit Field Locations and Descriptions

Power Down Control Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

00B4 Rsvd DBL_DIS

00B5 Rsvd 1 1 CLK1_DIS CLK0_DIS

00B6 Rsvd PLL1_DIS Rsvd

00B7 Q7_DIS Q6_DIS Q5_DIS Q4_DIS Q3_DIS Q2_DIS Q1_DIS Q0_DIS

00B8 Rsvd DPLL1_DIS DPLL0_DIS CALRST1 CALRST0

Power Down Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

DBL_DIS R/W 0b

Controls whether Crystal Input Frequency is Doubled before Being used in PLL0 or PLL1:

0 = 2x Actual Crystal Frequency Used

1 = Actual Crystal Frequency Used

CLKm_DIS R/W 0b

Disable Control for Input Reference m:

0 = Input Reference m is Enabled

1 = Input Reference m is Disabled

PLL1_DIS R/W 0b

Disable Control for Analog PLL1:

0 = PLL1 Enabled

1 = Analog PLL1 Disabled

Qm_DIS R/W 0b

Disable Control for Output Qm, nQm:

0 = Output Qm, nQm functions normally

1 = All logic associated with Output Qm, nQm is Disabled & Driver in High-Impedance

state

DPLLm_DIS R/W 0b

Disable Control for Digital PLLm:

0 = Digital PLLm Enabled

1 = Digital PLLm Disabled

CALRSTm R/W 0b

Reset Calibration Logic for APLLm:

0 = Calibration Logic for APLLm Enabled

1 = Calibration Logic for APLLm Disabled

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 38 REVISION 5 07/09/15

Table 6Q. Input Monitor Control Register Bit Field Locations and Descriptions

Table 6R. Interrupt Enable Control Register Bit Field Locations and Descriptions

Input Monitor Control Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

00B9 Rsvd LOS_0[16]

00BA LOS_0[15:8]

00BB LOS_0[7:0]

00BC Rsvd LOS_1[16]

00BD LOS_1[15:8]

00BE LOS_1[7:0]

00BF Rsvd Rsvd

00C0 Rsvd

00C1 Rsvd

00C2 Rsvd Rsvd

00C3 Rsvd

00C4 Rsvd

00C5 Rsvd

00C6 Rsvd

Input Monitor Control Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

LOS_m[16:0] R/W 1FFFFh Number of Input Monitoring clock periods before Input Reference m is considered to be

missed (soft alarm). Minimum setting is 3.

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Interrupt Enable Control Register Block Field Locations

Address (Hex)D7D6 D5 D4D3D2D1D0

00C7 LOL1_EN LOL0_EN HOLD1_EN HOLD0_EN Rsvd Rsvd LOS1_EN LOS0_EN

Interrupt Enable Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

LOLm_EN R/W 0b

Interrupt Enable Control for Loss-of-Lock Interrupt Status Bit for PLLm:

0 = LOLm_INT register bit will not affect status of nINT output signal

1 = LOLm_INT register bit will affect status of nINT output signal

HOLDm_EN R/W 0b

Interrupt Enable Control for Holdover Interrupt Status Bit for PLLm:

0 = HOLDm_INT register bit will not affect status of nINT output signal

1 = HOLDm_INT register bit will affect status of nINT output signal

LOSm_EN R/W 0b

Interrupt Enable Control for Loss-of-Signal Interrupt Status Bit for Input Reference m:

0 = LOSm_INT register bit will not affect status of nINT output signal

1 = LOSm_INT register bit will affect status of nINT output signal

8T49N287 DATA SHEET

REVISION 5 07/09/15 39 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6S. Digital Phase Detector Control Register Bit Field Locations and Descriptions

Table 6T. Interrupt Status Register Bit Field Locations and Descriptions

This register contains “sticky” bits for tracking the status of the various alarms. Whenever an alarm occurs, the appropriate Interrupt Status bit

will be set. The Interrupt Status bit will remain asserted even after the original alarm goes away. The Interrupt Status bits remain asserted until

explicitly cleared by a write of a ‘1’ to the bit over the serial port. This type of functionality is referred to as Read / Write-1-to-Clear (R/W1C).

0200 LOL1_INT LOL0_INT HOLD1_INT HOLD0_INT Rsvd Rsvd LOS1_INT LOS0_INT

0201 Rsvd

0202 Rsvd

0203 Rsvd

LOLm_INT R/W1C 0b

Interrupt Status Bit for Loss-of-Lock on PLLm:

0 = No Loss-of-Lock alarm flag on PLLm has occurred since the last time this register

bit was cleared

1 = At least one Loss-of-Lock alarm flag on PLLm has occurred since the last time this

HOLDm_INT R/W1C 0b

Interrupt Status Bit for Holdover on PLLm:

0 = No Holdover alarm flag on PLLm has occurred since the last time this register bit

was cleared

1 = At least one Holdover alarm flag on PLLm has occurred since the last time this

LOSm_INT R/W1C 0b

Interrupt Status Bit for Loss-of-Signal on Input Reference m:

0 = No Loss-of-Signal alarm flag on Input Reference m has occurred since the last time

this register bit was cleared

1 = At least one Loss-of-Signal alarm flag on Input Reference m has occurred since the

last time this register bit was cleared

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Digital Phase Detector Control Register Block Field Locations

ddress (Hex)D7D6D5D4D3D2D1D0

00C8 27h

00C9 Rsvd 1 Rsvd 1 Rsvd Rsvd

00CA 27h

00CB Rsvd 1 Rsvd 1 Rsvd Rsvd

Digital Phase Detector Control Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Interrupt Status Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

Interrupt Status Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 40 REVISION 5 07/09/15

Table 6U. Output Phase Adjustment Status Register Bit Field Locations and Descriptions

Table 6V. Digital PLL0 Status Register Bit Field Locations and Descriptions

Output Phase Adjustment Status Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

0204 PA_BUSY7 PA_BUSY6 PA_BUSY5 PA_BUSY4 PA_BUSY3 PA_BUSY2 PA_BUSY1 PA_BUSY0

Output Phase Adjustment Status Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

PA_BUSYm R/O -

Phase Adjustment Event Status for output Qm, nQm:

0 = No phase adjustment is currently in progress on output Qm, nQm

1 = Phase adjustment still in progress on output Qm, nQm. Do not initiate any new

phase adjustment at this time

Digital PLL0 Status Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1 D0

0205 Rsvd EXTLOS0 Rsvd CURR_REF0[2:0]

0206 Rsvd Rsvd Rsvd Rsvd Rsvd

0207 Rsvd Rsvd

0208 Rsvd

0209 Rsvd

020A Rsvd Rsvd

020B Rsvd

020C Rsvd

020D Rsvd

020E Rsvd

Digital PLL0 Status Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

CURR_REF0[2:0] R/O -

Currently Selected Reference Status for Digital PLL0:

000 - 011 = No reference currently selected

100 = Input Reference 0 (CLK0, nCLK0) selected

101 = Input Reference 1 (CLK1, nCLK1) selected

110 = Reserved

111 = Reserved

EXTLOS0 R/O -

External Loopback signal lost for PLL0:

0 = PLL0 has a valid feedback reference signal

1 = PLL0 has lost the external feedback reference signal and is no longer locked

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

REVISION 5 07/09/15 41 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 6W. Digital PLL1 Status Register Bit Field Locations and Descriptions

Table 6X. General Purpose Input Status Register Bit Field Locations and Descriptions

Digital PLL1 Status Register Block Field Locations

Address (Hex)D7D6D5 D4 D3 D2 D1 D0

020F Rsvd EXTLOS1 Rsvd CURR_REF1[2:0]

0210 Rsvd Rsvd Rsvd Rsvd Rsvd

0211 Rsvd Rsvd

0212 Rsvd

0213 Rsvd

0214 Rsvd Rsvd

0215 Rsvd

0216 Rsvd

0217 Rsvd

0218 Rsvd

Digital PLL1 Status Register Block Field Descriptions

Bit Field Name

Field

Type Default Value Description

CURR_REF1[2:0] R/O -

Currently Selected Reference Status for Digital PLL1:

000 - 011 = No reference currently selected

100 = Input Reference 0 (CLK0, nCLK0) selected

101 = Input Reference 1 (CLK1, nCLK1) selected

110 = Reserved

111 = Reserved

EXTLOS1 R/O -

External Loopback signal lost for PLL1:

0 = PLL1 has a valid feedback reference signal

1 = PLL1 has lost the external feedback reference signal and is no longer locked

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

Global Interrupt Status Register Block Field Locations

Address (Hex)D7D6D5D4D3D2D1D0

0219 Rsvd GPI[3] GPI[2] GPI[1] GPI[0]

General Purpose Input Status Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

GPI[3:0] R/O -

Shows current values on GPIO[3:0] pins that are configured as General-Purpose Inputs.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 42 REVISION 5 07/09/15

Table 6Y. Global Interrupt Status Register Bit Field Locations and Descriptions

Global Interrupt Status Register Block Field Locations

Address (Hex) D7 D6 D5 D4 D3 D2 D1 D0

021A Rsvd Rsvd INT

021B Rsvd

021C Rsvd CALI_DBIT0[5:0]

021D Rsvd CALI_DBIT1[5:0]

021E Rsvd Rsvd Rsvd BOOTFAIL

021F Rsvd Rsvd Rsvd Rsvd nEEP_CRC Rsvd Rsvd EEPDONE

Global Interrupt Status Register Block Field Descriptions

Bit Field Name Field Type Default Value Description

INT R/O -

Device Interrupt Status:

0 = No Interrupt Status bits that are enabled are asserted (nINT pin released)

1 = At least one Interrupt Status bit that is enabled is asserted (nINT pin asserted low)

BOOTFAIL R/O - Reading of Serial EEPROM failed. Once set this bit is only cleared by reset.

nEEP_CRC R/O -

EEPROM CRC Error (Active Low):

0 = EEPROM was detected and read, but CRC check failed - please reset the device

via the nRST pin to retry (serial port is locked)

1 = No EEPROM CRC Error

EEPDONE R/O - Serial EEPROM Read cycle has completed. Once set this bit is only cleared by reset.

CALI_DBITn[5:0] R/O - Indicates current digital bit setting for PLLn

Rsvd R/W - Reserved. Always write 0 to this bit location. Read values are not defined.

8T49N287 DATA SHEET

REVISION 5 07/09/15 43 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Absolute Maximum Ratings

NOTE: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These ratings are stress

specifications only. Functional operation of product at these conditions or any conditions beyond those listed in the DC Characteristics or AC

Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods may affect product reliability.

Supply Voltage, VCC 3.63V

Inputs, VI

OSCI

Other Input

0V to 2V

-0.5V to VCC + 0.5V

Outputs, VO (Q[0:7], nQ[0:7]) -0.5V to VCCOX + 0.5V

Outputs, VO (GPIO[0:3], SDATA, SCLK, nINT) -0.5V to VCC + 0.5V

Outputs, IO (Q[0:7], nQ[0:7])

Continuous Current

Surge Current



40mA

65mA

Outputs, IO (GPIO[0:3], SDATA, SCLK, nINT)

Continuous Current

Surge Current



8mA

13mA

Junction Temperature, TJ125C

Storage Temperature, TSTG -65C to 150C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

Supply Voltage Characteristics

Table 7A. Power Supply Characteristics, VCC = 3.3V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE 1: ICC and ICCA are included in IEE when Q[0:7] configured for LVPECL logic levels.

NOTE 2: Internal dynamic switching current at maximum fOUT is included.

Item Rating

Symbol Parameter Test Conditions Minimum Typical Maximum Units

VCC Core Supply Voltage 3.135 3.3 3.465 V

VCCA Analog Supply Voltage VCC – 0.13 3.3 VCC V

ICC Core Supply Current; 

NOTE 1 74 100 mA

ICCA

Analog Supply Current;

NOTE 1

PLL0 and PLL1 Enabled 206 265 mA

Analog PLL1, Digital PLL1, and

Calibration Logic for analog PLL1 Disabled 122 187 mA

IEE

Power Supply Current;

NOTE 2

Q[0:7] Configured for LVPECL Logic Levels,

Outputs Unloaded 562 735 mA

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 44 REVISION 5 07/09/15

Table 7B. Power Supply Characteristics, VCC = 2.5V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE 1: ICC and ICCA are included in IEE when Q[0:7] configured for LVPECL logic levels.

NOTE 2: Internal dynamic switching current at maximum fOUT is included.

Table 7C. Maximum Output Supply Current, VCC = 3.3V ±5% or 2.5V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE: Internal dynamic switching current at maximum fOUT is included.

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

Symbol Parameter Test Conditions Minimum Typical Maximum Units

VCC Core Supply Voltage 2.375 2.5 2.625 V

VCCA Analog Supply Voltage VCC – 0.13 2.5 VCC V

ICC

Core Supply Current; 

NOTE 1 72 95 mA

ICCA

Analog Supply Current;

NOTE 1

PLL0 and PLL1 Enabled 201 260 mA

Analog PLL1, Digital PLL1, and

Calibration Logic for analog PLL1 Disabled 119 182 mA

IEE

Power Supply Current;

NOTE 2

Q[0:7] Configured for LVPECL Logic Levels,

Outputs Unloaded 533 695 mA

Symbol Parameter

Test

Conditions

VCCOx = 3.3V ±5% VCCOx = 2.5V ±5% VCCOx = 1.8V ±5%

UnitsLVPECL LVDS HCSL LVCMOS LVPECL LVDS HCSL LVCMOS LVCMOS

ICCO0

Q0, nQ0 Output 

Supply Current

Outputs

Unloaded 50 60 50 55 40 50 40 45 35 mA

ICCO1

Q1, nQ1 Output 

Supply Current

Outputs

Unloaded 50 60 50 55 40 50 40 45 35 mA

ICCO2

Q2, nQ2 Output 

Supply Current

Outputs

Unloaded 80 90 80 80 70 80 70 70 60 mA

ICCO3

Q3, nQ3 Output 

Supply Current

Outputs

Unloaded 80 90 80 80 70 80 70 70 60 mA

ICCO4

Q4, nQ4 Output 

Supply Current

Outputs

Unloaded 55 65 55 55 45 55 45 45 40 mA

ICCO5

Q5, nQ5 Output 

Supply Current

Outputs

Unloaded 55 65 55 55 45 55 45 45 40 mA

ICCO6

Q6, nQ6 Output 

Supply Current

Outputs

Unloaded 55 65 55 55 45 55 45 45 40 mA

ICCO7

Q7, nQ7 Output 

Supply Current

Outputs

Unloaded 55 65 55 55 45 55 45 45 40 mA

8T49N287 DATA SHEET

REVISION 5 07/09/15 45 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

DC Electrical Characteristics

Table 8A. LVCMOS/LVTTL DC Characteristics, VEE = 0V, TA = -40°C to 85°C

NOTE 1: Use of external pull-up resistors is recommended.

Table 8B. Differential Input DC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE: CLKx denotes CLK0, CLK1. nCLKx denotes nCLK0, nCLK1.

NOTE 1: VIL should not be less than -0.3V. VIH should not be higher than VCC.

NOTE 2: Common mode voltage is defined as the cross-point.

Symbol Parameter Test Conditions Minimum Typical Maximum Units

VIH Input High Voltage VCC = 3.3V 2 VCC +0.3 V

VCC = 2.5V 1.7 VCC +0.3 V

VIL Input Low Voltage VCC = 3.3V -0.3 0.8 V

VCC = 2.5V -0.3 0.7 V

IIH Output

High Voltage

PLL_BYP, S_A0 VCC = VIN = 3.465V or 2.625V 150 µA

nRST, SDATA, SCLK VCC = VIN = 3.465V or 2.625V 5 µA

GPIO[3:0] VCC = VIN = 3.465V or 2.625V 1 mA

IIL

PLL_BYP, S_A0 VCC = 3.465V or 2.625V, VIN = 0V -5 µA

Output

Low Voltage

nRST, SDATA, SCLK VCC = 3.465V or 2.625V, VIN = 0V -150 µA

GPIO[3:0] VCC = 3.465V or 2.625V, VIN = 0V -1 mA

VOH

Output

High Voltage

nINT, 

SDATA,SCLK; NOTE 1 VCC = 3.3V ±5%, IOH = -5µA 2.6 V

GPIO[3:0] VCC = 3.3V ±5%, IOH = -50µA 2.6 V

nINT, 

SDATA,SCLK; NOTE 1 VCC = 2.5V ±5%, IOH = -5µA 1.8 V

GPIO[3:0] VCC = 2.5V ±5%, IOH = -50µA 1.8 V

VOL

Output

Low Voltage

nINT, SDATA,

SCLK; NOTE 1 VCC = 3.3V ±5% or 2.5V±5%, IOL = 5mA 0.5 V

GPIO[3:0] VCC = 3.3V ±5% or 2.5V±5%, IOL = 5mA 0.5 V

Symbol Parameter Test Conditions Minimum Typical Maximum Units

IIH Input High Current CLKx,

nCLKx VCC = VIN = 3.465V or 2.625V 150 µA

IIL Input Low Current CLKx VCC = 3.465V or 2.625V, VIN = 0V -5 µA

nCLKx VCC = 3.465V or 2.625V, VIN = 0V -150 µA

VPP Peak-to-Peak Voltage; NOTE 1 0.15 1.3 V

VCMR

Common Mode Input Voltage;

NOTE 1, 2 VEE VCC -1.2 V

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 46 REVISION 5 07/09/15

Table 8C. LVPECL DC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Qx denotes Q0, Q1, Q2, Q3, Q4, Q5, Q6, Q7. nQx denotes nQ0, nQ1, nQ2, nQ3, nQ4, nQ5, nQ6, nQ7.

NOTE 1: Outputs terminated with 50 to VCCOx – 2V.

Table 8D. LVDS DC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5% or 2.5V ±5%, VEE = 0V,

TA = -40°C to 85°C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Qx denotes Q0, Q1, Q2, Q3, Q4, Q5, Q6, Q7. nQx denotes nQ0, nQ1, nQ2, nQ3, nQ4, nQ5, nQ6, nQ7.

NOTE: Terminated 100 across Qx and nQx.

Table 8E. LVCMOS DC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VEE = 0V, TA = -40°C to 85°C

NOTE: Qx denotes Q0, Q1, Q2, Q3, Q4, Q5, Q6, Q7. nQx denotes nQ0, nQ1, nQ2, nQ3, nQ4, nQ5, nQ6, nQ7.

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

Symbol Parameter Test Conditions

VCCOx = 3.3V±5% VCCOx = 2.5V±5%

UnitsMinimum Typical Maximum Minimum Typical Maximum

VOH

Output 

High Voltage; 

NOTE 1

Qx,

nQx VCCOx - 1.3 VCCOx - 0.8 VCCOx - 1.4 VCCOx - 0.9 V

VOL

Output 

Low Voltage; 

NOTE 1

Qx,

nQx VCCOx - 1.95 VCCOx - 1.75 VCCOx - 1.95 VCCOx - 1.75 V

Symbol Parameter Test Conditions Minimum Typical Maximum Units

VOD Differential Output Voltage Qx, nQx 195 454 mV

VOD VOD Magnitude Change Qx, nQx 50 mV

VOS Offset Voltage Qx, nQx 1.1 1.375 V

VOS VOS Magnitude Change Qx, nQx 50 mV

Symbol Parameter

Test

Conditions

VCCOx = 3.3V±5% VCCOx = 2.5V±5% VCCOx = 1.8V ±5%

UnitsMinimum Typical Maximum Minimum Typical Maximum Minimum Typical Maximum

VOH

Output 

High Voltage

Qx, 

nQx IOH = -8mA 2.6 1.8 1.1 V

VOL

Output 

Low Voltage

Qx, 

nQx IOL = 8mA 0.5 0.5 0.5 V

8T49N287 DATA SHEET

REVISION 5 07/09/15 47 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 9. Input Frequency Characteristics, VCC = 3.3V±5% or 2.5V±5%, TA = -40°C to 85°C

NOTE: CLKx denotes CLK0, CLK1. nCLKx denotes nCLK0, nCLK1.

NOTE 1: For the input reference frequency, the divider values must be set for the VCO to operate within its supported range.

NOTE 2. For optimal noise performance, the use of a quartz crystal is recommended. Refer to Applications Information, Overdriving the XTAL

Interface.

Table 10. Crystal Characteristics

Symbol Parameter Test Conditions Minimum Typical Maximum Units

fIN

Input Frequency;

NOTE 1

OSCI, OSCO

Using a crystal (See Table 10,

Crystal Characteristics) 10 40 MHz

Overdriving Crystal Input, Doubler

Logic Enabled; NOTE 2 10 62.5 MHz

Overdriving Crystal Input, Doubler

Logic Disabled; NOTE 2 16 125 MHz

CLKx, nCLKx 0.008 875 MHz

fSCLK Serial Port Clock SCLK Slave Mode 100 400 kHz

Parameter Test Conditions Minimum Typical Maximum Units

Mode of Oscillation Fundamental

Frequency 10 40 MHz

Equivalent Series Resistance (ESR) 15 

Load Capacitance (CL)12 pF

Frequency Stability (total) -100 100 ppm

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 48 REVISION 5 07/09/15

AC Electrical Characteristics

Table 11A. AC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5%, 2.5V ±5% or 1.8V ±5% (1.8V only

supported for LVCMOS outputs), TA = -40°C to 85°C

Symbol Parameter Test Conditions Minimum Typical Maximum Units

fVCO VCO Operating Frequency 3000 4000 MHz

fOUT

Output

Frequency

LVPECL, LVDS, HCSL

Q0, Q1, Q4, Q5, Q6, Q7 Outputs 0.008 1000 MHz

Q2, Q3 Outputs Integer Divide

Ratio & No Added Phase Delay 0.008 666.67 MHz

Q2, Q3 Outputs Non-integer

Divide and/or Added Phase Delay 0.008 400 MHz

LVCMOS 0.008 250 MHz

tR / tF

Output 

Rise and

Fall Times

LVPECL 20% to 80% 145 360 600 ps

LVDS 20% to 80% 100 230 400 ps

HCSL 20% to 80% 150 300 600 ps

LVCMOS; NOTE 1, 2

20% to 80%, VCCOx = 3.3V 180 350 600 ps

20% to 80%, VCCOx = 2.5V 200 350 550 ps

20% to 80%, VCCOx = 1.8V 200 410 650 ps

Output 

Slew Rate; 

NOTE 3

LVPECL

Measured on

Differential Waveform,

±150mV from Center

15V/ns

LVDS

Measured on

Differential Waveform,

±150mV from Center

0.5 4 V/ns

HCSL

VCCOx = 2.5V, fOUT  125MHz;

Measured on

Differential Waveform,

±150mV from Center

1.5 4 V/ns

VCCOx = 3.3V, fOUT  125MHz;

Measured on

Differential Waveform,

±150mV from Center

2.5 5.5 V/ns

tsk(b) Bank

Skew

LVPECL

Q0, nQ0, Q1, nQ1 NOTE 4, 5, 6, 7 75 ps

Q4, nQ4, Q5, nQ5 NOTE 4, 5, 6, 7 75 ps

Q6, nQ6, Q7, nQ7 NOTE 4, 5, 6, 7 75 ps

LVDS

Q0, nQ0, Q1, nQ1 NOTE 4, 5, 6, 7 75 ps

Q4, nQ4, Q5, nQ5 NOTE 4, 5, 6, 7 75 ps

Q6, nQ6, Q7,nQ7 NOTE 4, 5, 6, 7 75 ps

HCSL

Q0, nQ0, Q1, nQ1 NOTE 4, 5, 6, 7 75 ps

Q4, nQ4, Q5, nQ5 NOTE 4, 5, 6, 7 75 ps

Q6, nQ6, Q7, nQ7 NOTE 4, 5, 6, 7 75 ps

LVCMOS

Q0, nQ0, Q1, nQ1 NOTE 1, 4, 5, 7, 8 80 ps

Q4, nQ4, Q5, nQ5 NOTE 1, 4, 5, 7, 8 115 ps

Q6, nQ6, Q7, nQ7 NOTE 1, 4, 5, 7, 8 115 ps

8T49N287 DATA SHEET

REVISION 5 07/09/15 49 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is

mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium

has been reached under these conditions.

NOTE 1: Appropriate SE_MODE bit must be configured to select phase-aligned or phase-inverted operation.

NOTE 2: All Q and nQ outputs in phase-inverted operation

NOTE 3: Measured from -150mV to +150mV on the differential waveform (derived from Qx minus nQx). The signal must be monotonic through

the measurement region for rise and fall time. The 300mV measurement window is centered on the differential zero crossing.

NOTE 4: This parameter is guaranteed by characterization. Not tested in production.

NOTE 5: This parameter is defined in accordance with JEDEC Standard 65.

NOTE 6: Measured at the output differential cross point.

NOTE 7: Defined as skew within a bank of outputs at the same supply voltage and with equal load conditions running off the same PLL.

NOTE 8: Measured at VCCOx/2 of the rising edge. All Qx and nQx outputs phase-aligned.

NOTE 9:

Characterized in synthesizer mode. Duty cycle of bypassed signals (input reference clocks or crystal input) is not adjusted by the device.



NOTE 10: Tested in fast-lock operation after >20 minutes of locked operation to ensure holdover averaging logic is stable.

NOTE 11: This parameter is guaranteed by design.

NOTE 12: Using internal feedback mode configuration.

NOTE 13: Device programmed with SWMODEn = 0 (absorbs phase differences).

NOTE 14: Characterized with 8T49N287B-901 units (synthesizer mode).

odc

Output 

Duty

Cycle; 

NOTE 9

LVPECL, LVDS, HCSL fOUT  666.667MHz 45 50 55 %

fOUT > 666.667MHz 40 50 60 %

LVCMOS 40 50 60 %

Initial Frequency Offset; 

NOTE 10, 11, 12

Switchover or Entering / Leaving

Holdover State -50 50 ppb

Output Phase Change in Fully Hitless

Switching; NOTE 11, 12, 13

Switchover or Entering / Leaving

Holdover State 5ns

SSB(1k)

Single Sideband 

Phase Noise;

NOTE 14

1kHz 122.88MHz Output -123 dBc/Hz

SSB(10k) 10kHz 122.88MHz Output -131 dBc/Hz

SSB(100k) 100kHz 122.88MHz Output -134 dBc/Hz

SSB(1M) 1MHz 122.88MHz Output -147 dBc/Hz

SSB(10M) 10MHz 122.88MHz Output -153 dBc/Hz

SSB(30M) 30MHz 122.88MHz Output -154 dBc/Hz

Spurious Limit at

Offset; NOTE 15 800kHz 122.88MHz Output -83 dBc

tstartup Startup Time

Internal

OTP Startup;

NOTE 11

from VCC >80% to

First Output Clock Edge 110 150 ms

External 

EEPROM

Startup;

NOTE 11, 16

from VCC >80% to First Output

Clock Edge (0 retries);

I2C Frequency = 100kHz

150 200 ms

from VCC >80% to First Output

Clock Edge (0 retries);

I2C Frequency = 400kHz

130 150 ms

from VCC >80% to First Output

Clock Edge (31 retries);

I2C Frequency = 100kHz

925 1200 ms

from VCC >80% to First Output

Clock Edge (31 retries);

I2C Frequency = 400kHz

360 500 ms

SPO Static Phase Offset Variation; NOTE 17 fIN = fOUT = 156.25MHz -175 175 ps

Symbol Parameter Test Conditions Minimum Typical Maximum Units

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 50 REVISION 5 07/09/15

NOTE 15: Tested with all outputs operating at 122.88MHz.

NOTE 16: Assuming a clear I2C bus.

NOTE 17:

This parameter was measured using CLK0 as the reference input and CLK1 as the external feedback input. Characterized with

8T49N287-908.



Table 11B. HCSL AC Characteristics, VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5% or 2.5V ±5%, TA = -40°C to 85°C

NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is

mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium

has been reached under these conditions.

NOTE 1: Measurement taken from differential waveform.

NOTE 2: TSTABLE is the time the differential clock must maintain a minimum ±150mV differential voltage after rising/falling edges before it is

allowed to drop back into the VRB ±100mV differential range.

NOTE 3: Measurement taken from single ended waveform.

NOTE 4: Defined as the maximum instantaneous voltage including overshoot. 

NOTE 5: Defined as the minimum instantaneous voltage including undershoot. 

NOTE 6: Measured at crossing point where the instantaneous voltage value of the rising edge of Qn equals the falling edge of nQn.

NOTE 7: Refers to the total variation from the lowest crossing point to the highest, regardless of which edge is crossing. Refers to all crossing

points for this measurement.

NOTE 8: Defined as the total variation of all crossing voltages of rising Qn and falling nQn. This is the maximum allowed variance in VCROSS

for any particular system.

Symbol Parameter Test Conditions Minimum Typical Maximum Units

VRB

Ring-back Voltage Margin; 

NOTE 1, 2 -100 100 mV

tSTABLE

Time before VRB is allowed; 

NOTE 1, 2 500 ps

VMAX

Absolute Max. Output Voltage;

NOTE 3, 4 1150 mV

VMIN

Absolute Min. Output Voltage;

NOTE 3, 5 -300 mV

VCROSS

Absolute Crossing Voltage; 

NOTE 6, 7 230 550 mV

VCROSS

Total Variation of VCROSS Over

all Edges; NOTE 6, 8 140 mV

8T49N287 DATA SHEET

REVISION 5 07/09/15 51 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Table 12A. Typical RMS Phase Jitter (Synthesizer Mode), VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5%, 2.5V ±5% or

1.8V ±5% (1.8V only supported for LVCMOS outputs), TA = -40°C to 85°C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Fox part numbers: 277LF-40-18 and 277LF-38.88-2 used for 40MHz and 38.88MHz crystals, respectively.

NOTE: All outputs configured for the specific output type, as shown in the table.

NOTE 1: Characterized with 8T49N287-901.

NOTE 2: Characterized with 8T49N287-902.

NOTE 3: Characterized with 8T49N287-903.

NOTE 4: Characterized with 8T49N287-900.

NOTE 5: This frequency is not supported for LVCMOS operation.

NOTE 6: Qx and nQx are 180° out of phase.

Table 12B. Typical RMS Phase Jitter (Jitter Attenuator Mode), VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5%, 2.5V ±5%

or 1.8V ±5% (1.8V only supported for LVCMOS outputs), TA = -40°C to 85°C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Measured using a Rohde & Schwarz SMA100A as the input source.

NOTE: Fox part numbers: 277LF-40-18 and 277LF-38.88-2 used for 40MHz and 38.88MHz crystals, respectively.

NOTE: All outputs configured for the specific output type, as shown in the table.

NOTE 1: Characterized with 8T49N287-905.

NOTE 2: Characterized with 8T49N287-906.

NOTE 3: Characterized with 8T49N287-907.

NOTE 4: Characterized with 8T49N287-904.

NOTE 5: This frequency is not supported for LVCMOS operation.

NOTE 6: Qx and nQx are 180° out of phase.

Symbol Parameter Test Conditions LVPECL LVDS HCSL LVCMOS

NOTE 6 Units

tjit()

RMS Phase

Jitter

(Random)

Q0, Q1

fOUT = 122.88MHz, Integration Range:

12kHz - 20MHz; NOTE 1 282 299 280 287 fs

fOUT = 156.25MHz, Integration Range:

12kHz - 20MHz; NOTE 2 265 264 263 270 fs

fOUT = 622.08MHz, Integration Range:

12kHz - 20MHz; NOTE 3 289 266 265 N/A

(NOTE 5)fs

Q2, Q3 Integer;

NOTE 1

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 312 326 304 318 fs

Q2, Q3

Fractional;

NOTE 4

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 269 280 261 263 fs

Q4, Q5, Q6, Q7; 

NOTE 1

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 302 321 295 301 fs

Symbol Parameter Test Conditions LVPECL LVDS HCSL LVCMOS

NOTE 6 Units

tjit()

RMS Phase

Jitter

(Random)

Q0, Q1

fOUT = 122.88MHz, Integration Range:

12kHz - 20MHz; NOTE 1 285 299 280 275 fs

fOUT = 156.25MHz, Integration Range:

12kHz - 20MHz; NOTE 2 261 252 264 274 fs

fOUT = 622.08MHz, Integration Range:

12kHz - 20MHz; NOTE 3 221 203 202 N/A

(NOTE 5)fs

Q2, Q3 Integer;

NOTE 1

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 312 327 306 306 fs

Q2, Q3

Fractional;

NOTE 4

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 271 282 263 267 fs

Q4, Q5, Q6, Q7; 

NOTE 1

fOUT = 122.88MHz,

Integration Range: 12kHz - 20MHz 308 320 295 288 fs

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 52 REVISION 5 07/09/15

Table 13. PCI Express Jitter Specifications, VCC = 3.3V ±5% or 2.5V ±5%, VCCOx = 3.3V ±5% or 2.5V ±5%,

TA = -40°C to 85°C

NOTE: VCCOx denotes VCCO0, VCCO1, VCCO2, VCCO3, VCCO4, VCCO5, VCCO6, VCCO7.

NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is

mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium

has been reached under these conditions.

NOTE 1: Peak-to-Peak jitter after applying system transfer function for the Common Clock Architecture. Maximum limit for PCI Express Gen 1

NOTE 2: RMS jitter after applying the two evaluation bands to the two transfer functions defined in the Common Clock Architecture and

reporting the worst case results for each evaluation band. Maximum limit for PCI Express Generation 2 is 3.1ps RMS for tREFCLK_HF_RMS

(High Band) and 3.0ps RMS for tREFCLK_LF_RMS (Low Band).

NOTE 3: RMS jitter after applying system transfer function for the common clock architecture. This specification is based on the PCI Express

Base Specification Revision 0.7, October 2009 and is subject to change pending the final release version of the specification. 

NOTE 4: This parameter is guaranteed by characterization. Not tested in production.

NOTE 5: Outputs configured for HCSL mode. Fox 277LF-40-18 crystal used with doubler logic enabled.

Symbol Parameter Test Conditions Minimum Typical Maximum

PCIe Industry

Specification Units

(PCIe Gen 1)

Phase Jitter

Peak-to-Peak; 

NOTE 1, 4, 5

ƒ = 100MHz, 40MHz Crystal Input,

Evaluation Band: 0Hz - Nyquist (Clock Frequency/2) 816 86 ps

tREFCLK_HF_RMS

(PCIe Gen 2)

Phase Jitter RMS; 

NOTE 2, 4, 5

ƒ = 100MHz, 40MHz Crystal Input,

High Band: 1.5MHz - Nyquist (Clock Frequency/2) 0.8 1.8 3.1 ps

tREFCLK_LF_RMS

(PCIe Gen 2)

Phase Jitter RMS; 

NOTE 2, 4, 5

ƒ = 100MHz, 40MHz Crystal Input,

Low Band: 10kHz - 1.5MHz 0.03 0.5 3.0 ps

tREFCLK_RMS

(PCIe Gen 3)

Phase Jitter RMS; 

NOTE 3, 4, 5

ƒ = 100MHz, 40MHz Crystal Input,

Evaluation Band: 0Hz - Nyquist (Clock Frequency/2) 0.2 0.5 0.8 ps

8T49N287 DATA SHEET

REVISION 5 07/09/15 53 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Typical Phase Noise at 156.25MHz



Noise PowerdBc/Hz

Offset Frequency (Hz)

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 54 REVISION 5 07/09/15

Applications Information

Overdriving the Crystal Interface

The OSCI input can be overdriven by an LVCMOS driver or by one

side of a differential driver through an AC coupling capacitor. The

OSCO pin can be left floating. The amplitude of the input signal

should be between 500mV and 1.8V and the slew rate should not be

less than 0.2V/ns. For 3.3V LVCMOS inputs, the amplitude must be

reduced from full swing to at least half the swing in order to prevent

signal interference with the power rail and to reduce internal noise.

Figure 5A shows an example of the interface diagram for a high

speed 3.3V LVCMOS driver. This configuration requires that the sum

of the output impedance of the driver (Ro) and the series resistance

(Rs) equals the transmission line impedance. In addition, matched

termination at the crystal input will attenuate the signal in half. This

can be done in one of two ways. First, R1 and R2 in parallel should

equal the transmission line impedance. For most 50 applications,

R1 and R2 can be 100. This can also be accomplished by removing

R1 and changing R2 to 50. The values of the resistors can be

increased to reduce the loading for a slower and weaker LVCMOS

driver. Figure 5B shows an example of the interface diagram for an

LVPECL driver. This is a standard LVPECL termination with one side

of the driver feeding the OSCI input. It is recommended that all

components in the schematics be placed in the layout. Though some

components might not be used, they can be utilized for debugging

purposes. The datasheet specifications are characterized and

guaranteed by using a quartz crystal as the input.

Figure 5A. General Diagram for LVCMOS Driver to XTAL Input Interface

Figure 5B. General Diagram for LVPECL Driver to XTAL Input Interface

LVCMOS_Driver

Zo = 50Ω

Zo = Ro + Rs

100

VCC OSCO

OSCI

0.1μF

LVPECL_Driver

Zo = 50Ω

0.1μF

OSCO

OSCI

Zo = 50Ω

8T49N287 DATA SHEET

REVISION 5 07/09/15 55 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Wiring the Differential Input to Accept Single-Ended Levels

Figure 6 shows how a differential input can be wired to accept single

ended levels. The reference voltage VREF = VCC/2 is generated by

the bias resistors R1 and R2. The bypass capacitor (C1) is used to

help filter noise on the DC bias. This bias circuit should be located as

close to the input pin as possible. The ratio of R1 and R2 might need

to be adjusted to position the VREF in the center of the input voltage

swing. For example, if the input clock swing is 2.5V and VCC = 3.3V,

R1 and R2 value should be adjusted to set VREF at 1.25V. The values

below are for when both the single ended swing and VCC are at the

same voltage. This configuration requires that the sum of the output

impedance of the driver (Ro) and the series resistance (Rs) equals

the transmission line impedance. In addition, matched termination at

the input will attenuate the signal in half. This can be done in one of

two ways. First, R3 and R4 in parallel should equal the transmission

line impedance. For most 50 applications, R3 and R4 can be 100.

The values of the resistors can be increased to reduce the loading for

slower and weaker LVCMOS driver. When using single-ended

signaling, the noise rejection benefits of differential signaling are

reduced. Even though the differential input can handle full rail

LVCMOS signaling, it is recommended that the amplitude be

reduced. The datasheet specifies a lower differential amplitude,

however this only applies to differential signals. For single-ended

applications, the swing can be larger, however VIL cannot be less

than -0.3V and VIH cannot be more than VCC + 0.3V. Suggest edge

rate faster than 1V/ns. Though some of the recommended

components might not be used, the pads should be placed in the

layout. They can be utilized for debugging purposes. The datasheet

specifications are characterized and guaranteed by using a

differential signal.

Figure 6. Recommended Schematic for Wiring a Differential Input to Accept Single-ended Levels

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 56 REVISION 5 07/09/15

3.3V Differential Clock Input Interface

CLKx/nCLKx accepts LVDS, LVPECL, LVHSTL, HCSL and other

differential signals. Both VSWING and VOH must meet the VPP and

VCMR input requirements. Figure 7A to Figure 7E show interface

examples for the CLKx/nCLKx input driven by the most common

driver types. The input interfaces suggested here are examples only.

Please consult with the vendor of the driver component to confirm the

driver termination requirements. For example, in Figure 7A, the input

termination applies for IDT open emitter LVHSTL drivers. If you are

using an LVHSTL driver from another vendor, use their termination

recommendation.

Figure 7A. CLKx/nCLKx Input Driven by an 

IDT Open Emitter LVHSTL Driver

Figure 7B. CLKx/nCLKx Input Driven by a 

3.3V LVPECL Driver

Figure 7C. CLKx/nCLKx Input Driven by a 

3.3V HCSL Driver

Figure 7D. CLKx/nCLKx Input Driven by a 

3.3V LVPECL Driver

Figure 7E. CLKx/nCLKx Input Driven by a 

3.3V LVDS Driver

50Ω

1.8V

Zo = 50Ω

CLK

nCLK

3.3V

LVHSTL

IDT

LVHSTL Driver

Differential

Input

CSL

Diff

nti

8T49N287 DATA SHEET

REVISION 5 07/09/15 57 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

2.5V Differential Clock Input Interface

CLKx/nCLKx accepts LVDS, LVPECL, LVHSTL and other differential

signals. Both VSWING and VOH must meet the VPP and VCMR input

requirements. Figure 8A to Figure 8D show interface examples for

the CLKx/nCLKx input driven by the most common driver types. The

input interfaces suggested here are examples only. Please consult

with the vendor of the driver component to confirm the driver

termination requirements. For example, in Figure 8A, the input

termination applies for IDT open emitter LVHSTL drivers. If you are

using an LVHSTL driver from another vendor, use their termination

recommendation.

Figure 8A. CLKx/nCLKx Input Driven by an 

IDT Open Emitter LVHSTL Driver

Figure 8B. CLKx/nCLKx Input Driven by a 

2.5V LVPECL Driver

Figure 8C. CLKx/nCLKx Input Driven by a 

2.5V LVPECL Driver

Figure 8D. CLKx/nCLKx Input Driven by a 

2.5V LVDS Driver



pen Emitte

TL Driv

Differential

nput

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 58 REVISION 5 07/09/15

Recommendations for Unused Input and Output Pins

Inputs:

CLKx/nCLKx Input

For applications not requiring the use one or more reference clock

inputs, both CLKx and nCLKx can be left floating. Though not

required, but for additional protection, a 1k resistor can be tied from

CLKx to ground. It is recommended that CLKx, nCLKx not be driven

with active signals when not enabled for use.

LVCMOS Control Pins

All control pins have internal pullups or pulldowns; additional

resistance is not required but can be added for additional protection.

A 1k resistor can be used.

Outputs:

LVP E C L Ou tp ut s

Any unused LVPECL output pairs can be left floating. We

recommend that there is no trace attached. Both sides of the

differential output pair should either be left floating or terminated.

LVDS Outputs

Any unused LVDS output pairs can be either left floating or

terminated with 100 across. If they are left floating there should be

no trace attached.

LVCMOS Outputs

Any LVCMOS output can be left floating if unused. There should be

no trace attached.

Termination for 3.3V LVPECL Outputs

The clock layout topology shown below is a typical termination for

LVPECL outputs. The two different layouts mentioned are

recommended only as guidelines.

The differential outputs generate ECL/LVPECL compatible outputs.

Therefore, terminating resistors (DC current path to ground) or

current sources must be used for functionality. These outputs are

designed to drive 50 transmission lines. Matched impedance

techniques should be used to maximize operating frequency and

minimize signal distortion. Figure 9A and Figure 9B show two

different layouts which are recommended only as guidelines. Other

suitable clock layouts may exist and it would be recommended that

the board designers simulate to guarantee compatibility across all

printed circuit and clock component process variations.

Figure 9A. 3.3V LVPECL Output Termination Figure 9B. 3.3V LVPECL Output Termination

84

3.3V

125

Zo = 50

Zo = 50Input

3.3V

8T49N287 DATA SHEET

REVISION 5 07/09/15 59 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Termination for 2.5V LVPECL Outputs

Figure 10A and Figure 10C show examples of termination for 2.5V

LVPECL driver. These terminations are equivalent to terminating 50

to VCCO – 2V. For VCCO = 2.5V, the VCCO – 2V is very close to ground

level. The R3 in Figure 10C can be eliminated and the termination is

shown in Figure 10B.

Figure 10A. 2.5V LVPECL Driver Termination Example

Figure 10B. 2.5V LVPECL Driver Termination Example

Figure 10C. 2.5V LVPECL Driver Termination Example

2.5V LVPECL Driver

CCO

= 2.5V

2.5V

50

250

62.5

–

2.5V LVPECL Driver

CCO

= 2.5V

2.5V

50

–

2.5V LVPECL Driver

VCCO = 2.5V

2.5V

50

–

8T49N287 DATA SHEET

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2.5V and 3.3V HCSL Recommended Termination

Figure 11A is the recommended source termination for applications

where the driver and receiver will be on a separate PCBs. This

termination is the standard for PCI Express™ and HCSL output types.

All traces should be 50Ω impedance single-ended or 100Ω

differential.

Figure 11A. Recommended Source Termination (where the driver and receiver will be on separate PCBs)

Figure 11B is the recommended termination for applications where a

point-to-point connection can be used. A point-to-point connection

contains both the driver and the receiver on the same PCB. With a

matched termination at the receiver, transmission-line reflections will

be minimized. In addition, a series resistor (Rs) at the driver offers

flexibility and can help dampen unwanted reflections. The optional

resistor can range from 0Ω to 33Ω. All traces should be 50Ω

impedance single-ended or 100Ω differential.

Figure 11B. Recommended Termination (where a point-to-point connection can be used)

0-0.2"

PCI Express

1-14"

Driver

0.5" Max

49. 9 +/ - 5%

22 t o 33 +/-5%

0.5 - 3.5"

Connector

PCI Express

Add- i n Card

PCI Express

0-0.2"

PCI Express

0-0.2"0-18"

Driver

0.5" Max

49.9 +/- 5%

0 to 33

8T49N287 DATA SHEET

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LVDS Driver Termination

For a general LVDS interface, the recommended value for the

termination impedance (ZT) is between 90 and 132. The actual

value should be selected to match the differential impedance (Z0) of

your transmission line. A typical point-to-point LVDS design uses a

100 parallel resistor at the receiver and a 100 differential

transmission-line environment. In order to avoid any

transmission-line reflection issues, the components should be

surface mounted and must be placed as close to the receiver as

possible. IDT offers a full line of LVDS compliant devices with two

types of output structures: current source and voltage source. The

standard termination schematic as shown in Figure 12A can be used

with either type of output structure. Figure 12B, which can also be

used with both output types, is an optional termination with center tap

capacitance to help filter common mode noise. The capacitor value

should be approximately 50pF. If using a non-standard termination, it

is recommended to contact IDT and confirm if the output structure is

current source or voltage source type. In addition, since these

outputs are LVDS compatible, the input receiver’s amplitude and

common-mode input range should be verified for compatibility with

the output.

LVDS

Driver

ZO  ZTZTLVDS

Receiver

Figure 12A.

LVDS

Driver

ZO  ZTLVDS

Receiver

Standard LVDS Termination

Figure 12B. Optional LVDS Termination

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VFQFN EPAD Thermal Release Path

In order to maximize both the removal of heat from the package and

the electrical performance, a land pattern must be incorporated on

the Printed Circuit Board (PCB) within the footprint of the package

corresponding to the exposed metal pad or exposed heat slug on the

package, as shown in Figure 13. The solderable area on the PCB, as

defined by the solder mask, should be at least the same size/shape

as the exposed pad/slug area on the package to maximize the

thermal/electrical performance. Sufficient clearance should be

designed on the PCB between the outer edges of the land pattern

and the inner edges of pad pattern for the leads to avoid any shorts.

While the land pattern on the PCB provides a means of heat transfer

and electrical grounding from the package to the board through a

solder joint, thermal vias are necessary to effectively conduct from

the surface of the PCB to the ground plane(s). The land pattern must

be connected to ground through these vias. The vias act as “heat

pipes”. The number of vias (i.e. “heat pipes”) are application specific

and dependent upon the package power dissipation as well as

electrical conductivity requirements. Thus, thermal and electrical

analysis and/or testing are recommended to determine the minimum

number needed. Maximum thermal and electrical performance is

achieved when an array of vias is incorporated in the land pattern. It

is recommended to use as many vias connected to ground as

possible. It is also recommended that the via diameter should be 12

to 13mils (0.30 to 0.33mm) with 1oz copper via barrel plating. This is

desirable to avoid any solder wicking inside the via during the

soldering process which may result in voids in solder between the

exposed pad/slug and the thermal land. Precautions should be taken

to eliminate any solder voids between the exposed heat slug and the

land pattern. Note: These recommendations are to be used as a

guideline only. For further information, please refer to the Application

Note on the Surface Mount Assembly of Amkor’s Thermally/

Electrically Enhance Lead frame Base Package, Amkor Technology.

Figure 13. P.C. Assembly for Exposed Pad Thermal Release Path – Side View (drawing not to scale)

Schematic and Layout Information

Schematics for 8T49N287 can be found on IDT.com. Please search

for the 8T49N287 device and click on the link for evaluation board

schematics.

Crystal Recommendation

This device was validated using FOX 277LF series through-hole

crystals including part #277LF-40-18 (40MHz) and #277LF-38.88-2

(38.88MHz). If a surface mount crystal is desired, we recommend

IDT Part #603-40-48 (40MHz) or #603-38.88-7 (38.88MHz) and FOX

Part #603-40-48 (40MHz) or #603-38.88-7 (38.88MHz).

I2C Serial EEPROM Recommendation

The 8T49N287 was designed to operate with most standard I2C

serial EEPROMs of 256 bytes or larger. Atmel AT24C04C was used

during device characterization and is recommended for use. Please

contact IDT for review of any other I2C EEPROM’s compatibility with

the 8T49N287.

SOLDERSOLDER PINPIN EXPOSED HEAT SLUG

PIN PAD PIN PADGROUND PLANE LAND PATTERN

(GROUND PAD)

THERMAL VIA

8T49N287 DATA SHEET

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PCI Express Application Note

PCI Express jitter analysis methodology models the system

response to reference clock jitter. The block diagram below shows the

most frequently used Common Clock Architecture in which a copy of

the reference clock is provided to both ends of the PCI Express Link.

In the jitter analysis, the transmit (Tx) and receive (Rx) serdes PLLs

are modeled as well as the phase interpolator in the receiver. These

transfer functions are called H1, H2, and H3 respectively. The overall

system transfer function at the receiver is:

Ht s H3 s H1 s H2 s–=

The jitter spectrum seen by the receiver is the result of applying this

system transfer function to the clock spectrum X(s) and is:

Ys Xs H3 sH1 s H2 s–=

In order to generate time domain jitter numbers, an inverse Fourier

Transform is performed on X(s)*H3(s) * [H1(s) - H2(s)].

PCI Express Common Clock Architecture

For PCI Express Gen 1, one transfer function is defined and the

evaluation is performed over the entire spectrum: DC to Nyquist (e.g

for a 100MHz reference clock: 0Hz – 50MHz) and the jitter result is

reported in peak-peak.

PCIe Gen 1 Magnitude of Transfer Function

For PCI Express Gen 2, two transfer functions are defined with 2

evaluation ranges and the final jitter number is reported in rms. The

two evaluation ranges for PCI Express Gen 2 are 10kHz – 1.5MHz

(Low Band) and 1.5MHz – Nyquist (High Band). The plots show the

individual transfer functions as well as the overall transfer function Ht.

PCIe Gen 2A Magnitude of Transfer Function

PCIe Gen 2B Magnitude of Transfer Function

For PCI Express Gen 3, one transfer function is defined and the

evaluation is performed over the entire spectrum. The transfer

function parameters are different from Gen 1 and the jitter result is

reported in RMS.

PCIe Gen 3 Magnitude of Transfer Function

For a more thorough overview of PCI Express jitter analysis

methodology, please refer to IDT Application Note PCI Express

Reference Clock Requirements.

8T49N287 DATA SHEET

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Power Dissipation and Thermal Considerations

The 8T49N287 is a multi-functional, high speed device that targets a wide variety of clock frequencies and applications. Since this device is

highly programmable with a broad range of features and functionality, the power consumption will vary as each of these features and functions

is enabled.

The 8T49N287 device was designed and characterized to operate within the ambient industrial temperature range of -40°C to +85°C. The

ambient temperature represents the temperature around the device, not the junction temperature. When using the device in extreme cases,

such as maximum operating frequency and high ambient temperature, external air flow may be required in order to ensure a safe and reliable

junction temperature. Extreme care must be taken to avoid exceeding 125°C junction temperature.

The power calculation examples below were generated using a maximum ambient temperature and supply voltage. For many applications, the

power consumption will be much lower. Please contact IDT technical support for any concerns on calculating the power dissipation for your

own specific configuration.

Power Domains

The 8T49N287 device has a number of separate power domains that can be independently enabled and disabled via register accesses (all power

supply pins must still be connected to a valid supply voltage). Figure 14 below indicates the individual domains and the associated power pins.



CLKInput&

DividerBlock

(CoreVCC)



Analog&DigitalPLL0

(VCCA&CoreVCC )



Analog&DigitalPLL1

(VCCA&CoreVCC )

OutputDivider/BufferQ0(V CC O 0)

OutputDivider/BufferQ1(V CC O 1)

OutputDivider/BufferQ2(V CC O 2)

OutputDivider/BufferQ3(V CC O 3)

OutputDivider/BufferQ4(V CC O 4)

OutputDivider/BufferQ5(V CC O 5)

OutputDivider/BufferQ6(V CC O 6)

OutputDivider/BufferQ7(V CC O 7)

Figure 14. 8T49N287 Power Domains

For the output paths shown above, there are three different structures that are used. Q0 and Q1 use one output path structure, Q2 and Q3 use

a second structure and Q[4:7] use a 3rd structure. Power consumption data will vary slightly depending on the structure used as shown in the

appropriate tables below.

Power Consumption Calculation

Determining total power consumption involves several steps:

1. Determine the power consumption using maximum current values for core and analog voltage supplies from Table 7A and Table 7B.

2. Determine the nominal power consumption of each enabled output path.

a. This consists of a base amount of power that is independent of operating frequency, as shown in Tabl e 1 5 A through Table 15I

(depending on the chosen output protocol).

b. Then there is a variable amount of power that is related to the output frequency. This can be determined by multiplying the output

frequency by the FQ_Factor shown in Table 15A through Table 15I.

3. All of the above totals are then summed.

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Thermal Considerations

Once the total power consumption has been determined, it is necessary to calculate the maximum operating junction temperature for the device

under the environmental conditions it will operate in. Thermal conduction paths, air flow rate and ambient air temperature are factors that can

affect this. The thermal conduction path refers to whether heat is to be conducted away via a heatsink, via airflow or via conduction into the

PCB through the device pads (including the ePAD). Thermal conduction data is provided for typical scenarios in Table 14 below. Please contact

IDT for assistance in calculating results under other scenarios.

Table 14. Thermal Resistance JA for 56-Lead VFQFN, Forced Convection

Current Consumption Data and Equations

Table 15A. 3.3V LVPECL Output Calculation Table

Table 15B. 3.3V HCSL Output Calculation Table

Table 15C. 3.3V LVDS Output Calculation Table

Table 15D. 2.5V LVPECL Output Calculation Table

Table 15E. 2.5V HCSL Output Calculation Table

Table 15F. 2.5V LVDS Output Calculation Table

JA by Velocity

Meters per Second 012

Multi-Layer PCB, JEDEC Standard Test Boards 16.0°C/W 12.14°C/W 11.02°C/W

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00593 40.1

Q2 0.01363 63.8

0.00591 42.9

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00582 40.1

Q2 0.01358 63.8

0.00553 43.1

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00627 48.6

Q2 0.01404 72.5

0.00630 51.3

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00373 32.8

Q2 0.01134 56.5

0.00369 35.7

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00354 32.9

Q2 0.01125 56.5

0.00353 35.7

Output FQ_Factor (mA/MHz) Base Current (mA)

Q0 0.00366 40.8

Q2 0.01148 64.5

0.00367 43.7

8T49N287 DATA SHEET

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Table 15G. 3.3V LVCMOS Output Calculation Table

Table 15H. 2.5V LVCMOS Output Calculation Table

Table 15I. 1.8V LVCMOS Output Calculation Table

Applying the values to the following equation will yield output current by frequency:

Qx Current (mA) = FQ_Factor * Frequency (MHz) + Base Current

where:

Qx Current is the specific output current according to output type and frequency

FQ_Factor is used for calculating current increase due to output frequency

Base Current is the base current for each output path independent of output frequency

The second step is to multiply the power dissipated by the thermal impedance to determine the maximum power gradient, using the following

equation:

TJ = TA + (JA * Pdtotal)

where:

TJ is the junction temperature (°C)

TA is the ambient temperature (°C)

JA is the thermal resistance value from Table 14, dependent on ambient airflow (°C/W)

Pdtotal is the total power dissipation of the 8T49N287 under usage conditions, including power dissipated due to loading (W)

Note that the power dissipation per output pair due to loading is assumed to be 27.95mW for LVPECL outputs and 44.5mW for HCSL outputs.

When selecting LVCMOS outputs, power dissipation through the load will vary based on a variety of factors including termination type and trace

length. For these examples, power dissipation through loading will be calculated using CPD (found in Table 2 ) and output frequency:

PdOUT = CPD * FOUT * VCCO2

where:

Pdout is the power dissipation of the output (W)

Cpd is the power dissipation capacitance (pF)

Fout is the output frequency of the selected output (MHz)

VCCO is the voltage supplied to the appropriate output (V)

Output Base Current (mA)

Q0 37.4

Q2 61.6

40.6

Output Base Current (mA)

Q0 30.8

Q2 54.8

33.7

Output Base Current (mA)

Q0 27.4

Q2 51.4

30.3

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Example Calculations

Example 1. Common Customer Configuration (3.3V Core Voltage)

Output Output Type Frequency (MHz) VCCO

Q0 LVPECL 245.76 3.3

Q1 LVPECL 245.76 3.3

Q2 LVPECL 33.333 3.3

Q3 LVPECL 33.333 3.3

Q4 LVDS 125 3.3

Q5 LVDS 125 3.3

Q6 LVCMOS 25 3.3

Q7 LVCMOS 25 3.3

PLL0 Enabled

PLL1 Enabled

• Core Supply Current, ICC = 100mA (max)

• Analog Supply Current, ICCA = 265mA (max)

Q0 Current = 0.00593x245.76 + 40.1 = 41.56mA

Q1 Current = 0.00593x245.76 + 40.1 = 41.56mA

Q2 Current = 0.01363x33.333 + 63.8 = 64.25mA

Q3 Current = 0.01363x33.333 + 63.8 = 64.25mA

Q4 Current = 0.00630x125 + 51.3 = 52.09mA

Q5 Current = 0.00630x125 + 51.3 = 52.09mA

Q6 Current = 40.6mA

Q7 Current = 40.6mA

• Total Output Current = 397mA (max)

Total Device Current = 100mA + 265mA + 397mA = 762mA

Total Device Power = 3.465V * 762mA = 2640.3mW

• Power dissipated through output loading:

LVPECL = 27.95mW * 4 = 111.8mW

LVDS = already accounted for in device power

HCSL = n/a

LVCMOS = 14.5pF * 25MHz * 3.465V2 * 2 output pairs = 8.7mW

• Total Power = 2640.3mW + 111.8mW + 8.7mW = 2760.8mW or 2.8W

With an ambient temperature of 85°C and no airflow, the junction temperature is:

TJ = 85°C + 16.1°C/W * 2.8W = 130.1°C

This junction temperature is above the maximum allowable. In instances where maximum junction temperature is exceeded adjustments need

to be made to either airflow or ambient temperature. In this case, adjusting airflow to 1m/s (JA = 12.4°C/W) will reduce junction temperature

to 119.7C. If no airflow adjustments can be made, the maximum ambient operating temperature must be reduced by a minimum of 5.1°C.

8T49N287 DATA SHEET

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Example 2. High-Frequency Customer Configuration (3.3V Core Voltage)

Output Output Type Frequency (MHz) VCCO

Q0 LVDS 625.00 2.5

Q1 LVDS 625.00 2.5

Q2 LVPECL 161.133 2.5

Q3 LVPECL 161.133 2.5

Q4 HCSL 25 3.3

Q5 HCSL 25 3.3

Q6 HCSL 125 3.3

Q7 HCSL 156.25 3.3

PLL0 Enabled

PLL1 Disabled

• Core Supply Current, ICC = 100mA (max)

• Analog Supply Current, ICCA = 187mA (max, PLL0 path only)

Q0 Current = 0.00366x625 + 40.8 = 43.09mA

Q1 Current = 0.00366x625 + 40.8 = 43.09mA

Q2 Current = 0.01134x161.133 + 56.5 = 58.3mA

Q3 Current = 0.01134x161.133 + 56.5 = 58.3mA

Q4 Current = 0.00553x25 + 43.1 = 43.24mA

Q5 Current = 0.00553x25 + 43.1 = 43.24mA

Q6 Current = 0.00553x125 + 43.1 = 43.79mA

Q7 Current = 0.00553x156.25 + 43.1 = 43.96mA

• Total Output Current = 202.8mA (VCCO = 2.5V), 174.23mA (VCCO = 3.3V)

Total Device Power = 3.465V *(100mA + 187mA + 174.23mA) + 2.625V * 202.8mA = 2130.5mW

• Power dissipated through output loading:

LVPECL = 27.95mW * 2 = 55.9mW

LVDS = already accounted for in device power

HCSL = 44.5mW * 4 = 178mW

LVCMOS = n/a

Total Power = 2130.5mW + 55.9mW + 178mW = 2364.4mW or 2.36W

With an ambient temperature of 85°C, the junction temperature is:

TJ = 85°C + 16.1°C/W *2.36W = 123°C

This junction temperature is below the maximum allowable.

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Example 3. Low Power Customer Configuration (2.5V Core Voltage)

Output Output Type Frequency (MHz) VCCO

Q0 LVDS 156.25 2.5

Q1 LVDS 156.25 2.5

Q2 LVDS 161.133 2.5

Q3 LVCMOS 33.333 1.8

Q4 LVCMOS 25 1.8

Q5 LVCMOS 25 1.8

Q6 LVCMOS 25 1.8

Q7 LVDS 156.25 2.5

PLL0 Enabled

PLL1 Enabled

• Core Supply Current, ICC = 95mA (max)

• Analog Supply Current, ICCA = 260mA (max)

Q0 Current = 0.00366x156.25 + 40.8 = 41.37mA

Q1 Current = 0.00366x156.25 + 40.8 = 41.37mA

Q2 Current = 0.01148x161.133 + 64.5 = 66.35mA

Q3 Current = 51.4mA

Q4 Current = 30.3mA

Q5 Current = 30.3mA

Q6 Current = 30.3mA

Q7 Current = 0.00367x156.25 + 43.7 = 44.27mA

• Total Output Current = 193.36mA (VCCO = 2.5V), 142.3mA (VCCO = 1.8V)

Total Device Power = 2.625V *(95mA + 260mA + 193.36mA) + 1.89V * 142.3mA = 1708.4mW

• Power dissipated through output loading:

LVPECL = n/a

LVDS = already accounted for in device power

HCSL = n/a

LVCMOS_33.3MHz = 17pF * 33.3MHz * 1.89V2 * 1 output pair = 2.02mW

LVCMOS_25MHz = 12.5pF * 25MHz * 1.89V2 * 3 output pairs = 3.35mW

Total Power = 1708.4mW + 2.02mW + 3.35mW = 1714mW or 1.7W

With an ambient temperature of 85°C, the junction temperature is:

TJ = 85°C + 16.1°C/W *1.7W = 112.4°C

This junction temperature is below the maximum allowable.

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 70 REVISION 5 07/09/15

Reliability Information

Table 16. JA vs. Air Flow Table for a 56-Lead VFQFN

NOTE: Theta JA (JA)values calculated using a 4-layer JEDEC PCB (114.3mm x 101.6mm), with 2oz. (70µm) copper plating on all 4 layers.

Transistor Count

The transistor count for 8T49N287 is: 998,958

JA vs. Air Flow

Meters per Second 012

Multi-Layer PCB, JEDEC Standard Test Boards 16.0°C/W 12.14°C/W 11.02°C/W

8T49N287 DATA SHEET

REVISION 5 07/09/15 71 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

56-Lead VFQFN NL Package Outline

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 72 REVISION 5 07/09/15

56-Lead VFQFN NL Package Outline, continued

8T49N287 DATA SHEET

REVISION 5 07/09/15 73 FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR

Ordering Information

Table 17. Ordering Information

NOTE: For the specific, publicly available -ddd order codes, refer to FemtoClock NG Universal Frequency Translator Ordering Product

Information document. For custom -ddd order codes, please contact IDT for more information.

Table 18. Pin 1 Orientation in Tape and Reel Packaging

Part/Order Number Marking Package Shipping Packaging Temperature

8T49N287-dddNLGI IDT8T49N287-dddNLGI 56-Lead VFQFN, Lead-Free Tray -40C to +85C

8T49N287-dddNLGI8 IDT8T49N287-dddNLGI 56-Lead VFQFN, Lead-Free Tape & Reel, Pin 1

Orientation: EIA-481-C -40C to +85C

8T49N287-dddNLGI# IDT8T49N287-dddNLGI 56-Lead VFQFN, Lead-Free Tape & Reel, Pin 1

Orientation: EIA-481-D -40C to +85C

Part Number Suffix Pin 1 Orientation Illustration

NLGI8 Quadrant 1 (EIA-481-C)

NLGI# Quadrant 2 (EIA-481-D)

USER DIRECTION OF FEED

Correct Pin 1 ORIENTATION

CARRIER TAPE TOPSIDE

(Round Sprocket Holes)

USER DIRECTION OF FEED

Correct Pin 1 ORIENTATION

CARRIER TAPE TOPSIDE

(Round Sprocket Holes)

8T49N287 DATA SHEET

FEMTOCLOCK® NG OCTAL UNIVERSAL FREQUENCY TRANSLATOR 74 REVISION 5 07/09/15

Revision History Sheet

Rev Table Page Description of Change Date

3 General Description - first paragraph/last sentence, added HCSL.

Features - added HCSL in “Accepts up to two LVPECL....” bullet and “Generates 8

LVPECL...” bullet.

11/06/14

Table 11A 55 AC Characteristics Table - updated LVDS Rise/Fall Time maximum spec. from 500 to

400ps.

Miscellaneous content enhancement in:

Output Phase Control on Switchover section; Table 6A, Table 6C, Table 6E and 

Table 6G, and Pin Assignment format.

3/20/15

Table 11A 58

AC Characteristics Table - added fOUT minimum parameters.

Termination for 3.3V LVPECL Outputs updated Figure 9A.

Updated Crystal Recommendation.

6/01/15

511 "Device Start-up & Reset Behavior” - added second paragraph. 7/9/15

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