LMK00101SQX - Texas Instruments High-Performance Analog

LMK00101

January 16, 2012

Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator

with Universal Input

1.0 General Description

The LMK00101 is a high performance, low noise LVCMOS

fanout buffer which can distribute 10 ultra-low jitter clocks

from a differential, single ended, or crystal input. The

LMK00101 supports synchronous output enable for glitch free

operation. The ultra low-skew, low-jitter, and high PSRR

make this buffer ideally suited for various networking, tele-

com, server and storage area networking, RRU LO reference

distribution, medical and test equipment applications.

The core voltage can be set to 2.5 or 3.3 V, while the output

voltage can be set to 1.5, 1.8, 2.5 or 3.3 V. The LMK00101

can be easily configured through pin programming.

2.0 Target Applications

■LO Reference Distribution for RRU Applications

■SONET, Ethernet, Fibre Channel Line Cards

■Optical Transport Networks

■GPON OLT/ONU

■Server and Storage Area Networking

■Medical Imaging

■Portable Test and Measurement

■High-end A/V

3.0 Features

■10 LVCMOS/LVTTL Outputs, DC to 200 MHz

■Universal Input

—LVPECL

—LVDS

—HCSL

—SSTL

—LVCMOS / LVTTL

■Crystal Oscillator Interface

—Crystal Input Frequency: 10 to 40 MHz

■Output Skew: 6 ps

■Additive Phase Jitter

—30 fs at 156.25 MHz (12 kHz to 20 MHz)

■Low Propagation Delay

■Operates with 3.3 or 2.5 V Core Supply Voltage

■Adjustable Output Power Supply

—1.5 V, 1.8 V, 2.5 V, and 3.3 V For Each Bank

■32 pin LLP Package 5.0 x 5.0 x 0.8 mm

4.0 Functional Block Diagram

30146901

TRI-STATE® is a registered trademark of National Semiconductor Corporation.

LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

5.0 Connection Diagram

32-Pin LLP Package

30146902

6.0 Pin Descriptions

Pin # Pin Name Type Description

DAP DAP - The DAP should be grounded

1 CLKout0 Output LVCMOS Output

2, 6 Vddo Power Power Supply for Bank A (CLKout0 to CLKout4) CLKout pins.

19,23 Vddo Power Power Supply for Bank B (CLKout5 to CLKout9) CLKout pins.

3 CLKout1 Output LVCMOS Output

4,9,15,16,

21,25,26,32 GND GND Ground

5 CLKout2 Output LVCMOS Output

7 CLKout3 Output LVCMOS Output

8 CLKout4 Output LVCMOS Output

10 Vdd Power Supply for operating core and input buffer

11 OSCin Input Input for Crystal

12 OSCout Output Output for Crystal

13 CLKin0 Input Input Pin

14 CLKin0* Input Optional complimentary input pin

17 CLKout5 Output LVCMOS Output

18 CLKout6 Output LVCMOS Output

20 CLKout7 Output LVCMOS Output

22 CLKout8 Output LVCMOS Output

24 CLKout9 Output LVCMOS Output

27 CLKin1* Input Optional Complimentary Input Pin

28 CLKin1 Input Input Pin

29 SEL1 Input MSB for Input Clock Selection. This pin has an internal pull-down

resistor.

30 SEL0 Input LSB for Input Clock Selection. This pin has an internal pull-down

resistor.

31 OE Input Output Enable. This pin has an internal pull-down resistor.

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

7.0 Absolute Maximum Ratings (Note 1, Note 2)

If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for

availability and specifications.

Parameter Symbol Ratings Units

Core Supply Voltage Vdd -0.3 to 3.6 V

Output Supply Voltage Vddo -0.3 to 3.6 V

Input Voltage VIN -0.3 to Vdd + 0.3 V

Storage Temperature Range TSTG -65 to 150 °C

Lead Temperature (solder 4 s) TL+260 °C

Junction Temperature TJ+125 °C

8.0 Recommended Operating Conditions

Parameter Symbol Min Typ Max Units

Ambient Temperature TA-40 25 85 °C

Core Supply Voltage Vdd 2.375 3.3 3.45 V

Output Supply Voltage (Note 3) Vddo 1.425 3.3 Vdd V

Note 1: "Absolute Maximum Ratings" indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability

and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in

the Recommended Operating Conditions is not implied. The Recommended Operating Conditions indicate conditions at which the device is functional and the

device should not be operated beyond such conditions.

Note 2: This device is a high performance integrated circuit with ESD handling precautions. Handling of this device should only be done at ESD protected work

stations. The device is rated to a HBM-ESD of > 2.5 kV, a MM-ESD of > 250 V, and a CDM-ESD of > 1 kV.

Note 3: Vddo should be less than or equal to Vdd (Vddo ≤ Vdd)

9.0 Package Thermal Resistance

32-Lead LLP

Package Symbols Ratings Units

Thermal resistance from junction to ambient

on 4-layer Jedec board (Note 4)θJA 50 ° C/W

Thermal resistance from junction to case

(Note 5)θJC (DAP) 20 ° C/W

Note 4: Specification assumes 5 thermal vias connect to die attach pad to the embedded copper plane on the 4-layer Jedec board. These vias play a key role in

improving the thermal performance of the LLP. For best thermal dissipation it is recommended that the maximum number of vias be used on the board layout.

Note 5: Case is defined as the DAP (die attach pad).

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

10.0 Electrical Characteristics

(2.375 V ≤ Vdd ≤ 3.45 V, 1.425 ≤ Vddo ≤ Vdd, -40 °C ≤ TA ≤ 85 °C, Differential inputs. Typical values represent most likely

parametric norms at Vdd = Vddo = 3.3 V, TA = 25 °C, at the Recommended Operation Conditions at the time of product charac-

terization and are not guaranteed). Test conditions are: Ftest = 100 MHz, Load = 5 pF in parallel with 50 Ω unless otherwise stated.

Symbol Parameter Test Conditions Min Typ Max Units

Total Device Characteristics

Vdd Core Supply Voltage 2.375 2.5 or

3.3 3.45 V

Vddo Output Supply Voltage 1.425

1.5,1.8,

2.5, or

3.3

Vdd V

IVdd Core Current

No CLKin 16 25

Vddo = 3.3 V, Ftest = 100 MHz 24

Vddo = 2.5 V, Ftest = 100 MHz 20

IVddo[n] Current for Each Output

Vddo = 2.5 V,

OE = High, Ftest = 100 MHz 5

mAVddo= 3.3 V,

OE = High, Ftest = 100 MHz 7

OE = Low 0.1

IVdd + IVddo

Total Device Current with Loads on

all outputs

OE = High @ 100 MHz 95 mA

OE = Low 16

Power Supply Ripple Rejection (PSRR)

PSRR Ripple Induced

Phase Spur Level

100 kHz, 100 mVpp

Ripple Injected on

Vdd, Vddo = 2.5 V

-44 dBc

Outputs (Note 6)

Skew Output Skew Measured between outputs,

referenced to CLKout0 6 ps

fCLKout

Output Frequency

(Note 7) DC 200 MHz

tRise Rise/Fall Time

Vdd = 3.3 V, Vddo = 1.8 V, CL = 10 pF 500

Vdd = 2.5 V, Vddo = 2.5 V, CL = 10 pF 300

Vdd = 3.3 V, Vddo = 3.3 V, CL = 10 pF 200

VCLKoutLow Output Low Voltage 0.1

VCLKoutHigh Output High Voltage Vddo-

0.1

RCLKout Output Resistance 50 ohm

tjRMS Additive Jitter

fCLKout = 156.25 MHz,

CMOS input slew rate ≥ 2 V/ns

CL = 5 pF, BW = 12 kHz to 20 MHz

30 fs

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

Symbol Parameter Test Conditions Min Typ Max Units

Digital Inputs (OE, SEL0, SEL1)

VLow Input Low Voltage Vdd = 2.5 V 0.4

VHigh Input High Voltage Vdd = 2.5 V 1.3

Vdd = 3.3 V 1.6

IIH High Level Input Current 50 uA

IIL Low Level Input Current -5 5

CLKin0/0* and CLKin1/1* Input Clock Specifications, (Note 9, Note 10)

IIH High Level Input Current VCLKin = Vdd 20 uA

IIL

Low Level Input Current

(Note 8)VCLKin = 0 V -20 uA

VIH Input High Voltage Vdd V

VIL Input Low Voltage GND

VCM

Differential Input

Common Mode Input Voltage

(Note 12)

VID = 150 mV 0.5 Vdd-

1.2

VID = 350 mV 0.5 Vdd-

1.1

VID = 800 mV 0.5 Vdd-

0.9

VID Differential Input Voltage Swing CLKin driven differentially 0.15 1.5 V

OSCin/OSCout Pins

fOSCin Input Frequency (Note 7) Single-Ended Input, OSCout floating DC 200 MHz

fXTAL Crystal Frequency Input Range

Fundamental Mode Crystal

ESR < 200 Ω ( fXtal ≤ 30 MHz )

ESR < 120 Ω ( fXtal > 30 MHz )

(Note 11, Note 7)

10 40 MHz

COSCin Shunt Capacitance 1 pF

Note 6: AC Parameters for CMOS are dependent upon output capacitive loading

Note 7: Guaranteed by characterization.

Note 8: VIL should not go below -0.3 volts.

Note 9: See Section 12.1 Differential Voltage Measurement Terminology for definition of VID and VOD.

Note 10: Refer to application note AN-912 Common Data Transmission Parameters and their Definitions for more information.

Note 11: The ESR requirements stated are what is necessary in order to ensure that the Oscillator circuitry has no start up issues. However, lower ESR values

for the crystal might be necessary in order to stay below the maximum power dissipation requirements for that crystal.

Note 12: When using differential signals with VCM outside of the acceptable range for the specified VID, the clock must be AC coupled.

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

11.0 Typical Performance Characteristics

Unless otherwise specified: Vdd = Vddo = 3.3 V, TA = 20 °C, CL = 5 pF, CLKin driven differentially, input slew rate ≥ 2 V/ns.

RMS Jitter vs. CLKin Slew Rate @ 100 MHz

0.5 1.0 1.5 2.0 2.5 3.0

100

150

200

250

300

350

400

450

500

RMS JITTER (fs)

DIFFERENTIAL INPUT SLEW RATE (V/ns)

Fclk-100 MHz

Int. BW=1-20 MHz

-40 C

25 C

85 C

CLKin Source

30146941

Noise Floor vs. CLKin Slew Rate @ 100 MHz

0.5 1.0 1.5 2.0 2.5 3.0

-170

-165

-160

-155

-150

-145

-140

NOISE FLOOR (dBc/Hz)

DIFFERENTIAL INPUT SLEW RATE (V/ns)

Fclk=100 MHz

Foffset=20 MHz

-40 C

25 C

85 C

CLKin Source

30146974

LVCMOS Phase Noise @ 100 MHz (Note 13)

30146942

LVCMOS Output Swing vs. Frequency

0 200 400 600 800 1000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

OUTPUT SWING (V)

FREQUENCY (MHz)

Rterm=50 Ω

Vddo=1.5 V

Vddo=1.8 V

Vddo=2.5 V

Vddo=3.3 V

30146975

Iddo per Output vs Frequency

0 50 100 150 200 250

CURRENT (mA)

FREQUENCY (MHz)

Cload = 10 pF

Vddo = 1.5 V

Vddo = 1.8 V

Vddo = 2.5 V

Vddo = 3.3 V

30146976

Note 13: Test conditions: LVCMOS Input, slew rate ≥ 2 V/ns, CL = 5 pF in parallel with 50 Ω, BW = 1 MHz to 20 MHz.

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

12.0 Measurement Definitions

12.1 Differential Voltage Measurement Terminology

The differential voltage of a differential signal can be de-

scribed by two different definitions causing confusion when

reading datasheets or communicating with other engineers.

This section will address the measurement and description of

a differential signal so that the reader will be able to under-

stand and discern between the two different definitions when

used.

The first definition used to describe a differential signal is the

absolute value of the voltage potential between the inverting

and non-inverting signal. The symbol for this first measure-

ment is typically VID or VOD depending on if an input or output

voltage is being described.

The second definition used to describe a differential signal is

to measure the potential of the non-inverting signal with re-

spect to the inverting signal. The symbol for this second

measurement is VSS and is a calculated parameter. Nowhere

in the IC does this signal exist with respect to ground, it only

exists in reference to its differential pair. VSS can be measured

directly by oscilloscopes with floating references, otherwise

this value can be calculated as twice the value of VOD as de-

scribed in the first section

Figure 1 illustrates the two different definitions side-by-side

for inputs and Figure 2 illustrates the two different definitions

side-by-side for outputs. The VID and VOD definitions show

VA and VB DC levels that the non-inverting and inverting sig-

nals toggle between with respect to ground. VSS input and

output definitions show that if the inverting signal is consid-

ered the voltage potential reference, the non-inverting signal

voltage potential is now increasing and decreasing above and

below the non-inverting reference. Thus the peak-to-peak

voltage of the differential signal can be measured.

VID and VOD are often defined in volts (V) and VSS is often

defined as volts peak-to-peak (VPP).

30146912

FIGURE 1. Two Different Definitions for Differential Input Signals

30146913

FIGURE 2. Two Different Definitions for Differential Output Signals

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

13.0 Functional Description

The LMK00101 is a 10 output LVCMOS clock fanout buffer

with low additive jitter that can operate up to 200 MHz. It fea-

tures a 3:1 input multiplexer with a crystal oscillator input,

single supply or dual supply (lower power) operation, and pin-

programmable device configuration. The device is offered in

a 32-pin LLP package.

13.1 Vdd and Vddo Power Supplies (Note 14, Note 15)

Separate core and output supplies allow the output buffers to

operate at the same supply as the Vdd core supply (3.3 V or

2.5 V) or from a lower supply voltage (3.3 V, 2.5 V, 1.8 V, or

1.5 V). Compared to single-supply operation, dual supply op-

eration enables lower power consumption and output-level

compatibility.

Bank A (CLKout0 to CLKout4) and Bank B (CLKout5 to CLK-

out9) may also be operated at different Vddo voltages, provid-

ed neither Vddo voltage exceeds Vdd.

Note 14: Care should be taken to ensure the Vddo voltage does not exceed

the Vdd voltage to prevent turning-on the internal ESD protection circuitry.

Note 15: DO NOT DISCONNECT OR GROUND ANY OF THE Vddo PINS

as the Vddo pins are internally connected within an output bank.

13.2 CLOCK INPUTS

The LMK00101 has three different inputs, CLKin0/CLKin0*,

CLKin1/CLKin1*, and OSCin that can be driven in different

manners that are described in the following sections.

13.2.1 SELECTION OF CLOCK INPUT

Clock input selection is controlled using the SEL0 and SEL1

pins as shown in Table 1. Refer to Section 14.1 Driving the

Clock Inputs for clock input requirements. When CLKin0 or

CLKin1 is selected, the crystal circuit is powered down. When

OSCin is selected, the crystal oscillator will start-up and its

clock will be distributed to all outputs. Refer to Section 14.2

Crystal Interface for more information. Alternatively, OSCin

may be driven by a single ended clock, up to 200 MHz, instead

of a crystal.

TABLE 1. Input Selection

SEL1 SEL0 Input

0 0 CLKin0, CLKin0*

0 1 CLKin1, CLKin1*

1 X OSCin

(Crystal Mode)

13.2.1.1 CLKin/CLKin* Pins

The LMK00101 has two differential inputs (CLKin0/CLKin0*

and CLKin1/CLKin1*) that can be driven single-ended or dif-

ferentially. They can accept AC or DC coupled 3.3V/2.5V

LVPECL, LVDS, or other differential and singled ended sig-

nals that meet the input requirements under the “CLKin0/0*

and CLKin1/1* Input Clock Specifications” portion of the Sec-

tion 10.0 Electrical Characteristics and (Note 12). Refer to

Section 14.1 Driving the Clock Inputs for more details on driv-

ing the LMK00101 inputs.

In the event that a Crystal mode is not selected and the CLKin

pins do not have an AC signal applied to them, Table 2 fol-

lowing will be the state of the outputs.

TABLE 2. CLKinX Input vs. Output States

CLKinX CLKinX* Output State

Open Open Logic Low

Logic Low Logic Low Logic Low

Logic High Logic Low Logic High

Logic Low Logic High Logic Low

13.3 CLOCK OUTPUTS

The LMK00101 has 10 LVCMOS outputs.

13.3.1 Output Enable Pin

When the output enable pin is held High, the outputs are en-

abled. When it is held Low, the outputs are held in a Low state

as shown in Table 3.

TABLE 3. Output Enable Pin States

OE Outputs

Low Disabled (Hi-Z)

High Enabled

The OE pin is synchronized to the input clock to ensure that

there are no runt pulses. When OE is changed from Low to

High, the outputs will initially have an impedance of about

400 Ω to ground until the second falling edge of the input

clock. Starting with the second falling edge of the input clock,

the outputs will buffer the input. If the OE pin is taken from

Low to High when there is no input clock present, the outputs

will either go High or Low and stay a that state; they will not

oscillate. When the OE pin is taken from High to Low the out-

puts will become Low after the second falling edge of the clock

input and then will go to a Disabled (Hi-Z) state starting after

the next rising edge.

13.3.2 Using Less than Ten Outputs

Although the LMK00101 has 10 outputs, not all applications

will require all of these. In this case, the unused outputs

should be left floating with a minimum copper length (Note

16) to minimize capacitance. In this way, this output will con-

sume minimal output current because it has no load.

Note 16: For best soldering practices, the minimum trace length should

extend to include the pin solder mask. This way during reflow, the solder has

the same copper area as connected pins. This allows for good, uniform fillet

solder joints helping to keep the IC level during reflow.

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

14.0 Application Information

14.1 Driving the Clock Inputs

The LMK00101 has two differential inputs (CLKin0/CLKin0*

and CLKin1/CLKin1*) that can accept AC or DC coupled 3.3V/

2.5V LVPECL, LVDS, and other differential and single ended

signals that meet the input requirements specified in Sec-

tion 10.0 Electrical Characteristics. The device can accept a

wide range of signals due to its wide input common mode

voltage range (VCM) and input voltage swing (VID)/dynamic

range. AC coupling may also be employed to shift the input

signal to within the VCM range.

To achieve the best possible phase noise and jitter perfor-

mance, it is mandatory for the input to have a high slew rate

of 2 V/ns (differential) or higher. Driving the input with a lower

slew rate will degrade the noise floor and jitter. For this rea-

son, a differential input signal is recommended over single-

ended because it typically provides higher slew rate and

common-mode noise rejection.

While it is recommended to drive CLKin0 and CLKin1 with a

differential signal input, it is possible to drive them with a sin-

gle ended clock. The single-ended input slew rate should be

as high as possible to minimize performance degradation.

The CLKinX input has an internal bias voltage of about 1.4 V,

so the input can be AC coupled as shown in Figure 3, Figure

4, or Figure 5 depending upon the application.

30146938

FIGURE 3. Single-Ended LVCMOS Input, AC Coupling,

Near and Far End Termination

30146943

FIGURE 4. Single-Ended LVCMOS Input, AC Coupling,

Near End Termination

30146944

FIGURE 5. Single-Ended LVCMOS Input, AC Coupling,

Far End Termination

A single ended clock may also be DC coupled to CLKinX as

shown in Figure 6. If the DC coupled input swing has a com-

mon mode level near the devices internal bias of 1.4 V, then

only a 0.1 µF bypass cap is required on CLKinX*. Otherwise,

if the input swing is not optimally centered near the internal

bias voltage, then CLKinX* should be externally biased to the

midpoint voltage of the input swing. This can be achieved us-

ing external biasing resistors, RB1 and RB2, or another low-

noise voltage reference. The external bias voltage should be

within the specified input common voltage (VCM) range. This

will ensure the input swing crosses the threshold voltage at a

point where the input slew rate is the highest.

30146939

FIGURE 6. Single-Ended LVCMOS Input, DC Coupling

with Common Mode Biasing

If the crystal oscillator circuit is not used, it is possible to drive

the OSCin input with an single-ended external clock as shown

in Figure 7. Configurations similar to Figure 4 or Figure 5 could

also be used as long as the OSCout pin is left floating. The

input clock should be AC coupled to the OSCin pin, which has

an internally generated input bias voltage, and the OSCout

pin should be left floating. While OSCin provides an alterna-

tive input to multiplex an external clock, it is recommended to

use either differential input (CLKinX) since it offers higher op-

erating frequency, better common mode, improved power

supply noise rejection, and greater performance over supply

voltage and temperature variations.

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

30146903

FIGURE 7. Driving OSCin with a Single-Ended External

Clock

14.2 Crystal Interface

The LMK00101 has an integrated crystal oscillator circuit that

supports a fundamental mode, AT-cut crystal. The crystal in-

terface is shown in Figure 8.

30146904

FIGURE 8. Crystal Interface

The load capacitance (CL) is specific to the crystal, but usually

on the order of 18 to 20 pF. While CL is specified for the crys-

tal, the OSCin input capacitance (CIN = 1 pF typical) of the

device and PCB stray capacitance (CSTRAY ~ 1 to 3 pF) can

affect the discrete load capacitor values, C1 and C2. For the

parallel resonant circuit, the discrete capacitor values can be

calculated as follows:

CL = (C1 * C2) / (C1 + C2) + CIN + CSTRAY (1)

Typically, C1 = C2 for optimum symmetry, so Equation 1 can

be rewritten in terms of C1only:

CL = C12 / (2 * C1 ) + CIN + CSTRAY (2)

Finally, solve for C1:

C1 = (CL - CIN - CSTRAY) * 2 (3)

Section 10.0 Electrical Characteristics provides crystal inter-

face specifications with conditions that ensure start-up of the

crystal, but it does not specify crystal power dissipation. The

designer will need to ensure the crystal power dissipation

does not exceed the maximum drive level specified by the

crystal manufacturer. Overdriving the crystal can cause pre-

mature aging, frequency shift, and eventual failure. Drive level

should be held at a sufficient level necessary to start-up and

maintain steady-state operation.

The power dissipated in the crystal, PXTAL, can be computed

by:

PXTAL = IRMS2 * RESR * (1 + C0 / CL)2(4)

Where:

•IRMS is the RMS current through the crystal.

•RESR is the maximum equivalent series resistance

specified for the crystal.

•CL is the load capacitance specified for the crystal.

•C0 is the minimum shunt capacitance specified for the

crystal.

IRMS can be measured using a current probe (e.g. Tektronix

CT-6 or equivalent) placed on the leg of the crystal connected

to OSCout with the oscillation circuit active.

As shown in Figure 8, an external resistor, RLIM, can be used

to limit the crystal drive level if necessary. If the power dissi-

pated in the selected crystal is higher than the drive level

specified for the crystal with RLIM shorted, then a larger resis-

tor value is mandatory to avoid overdriving the crystal. How-

ever, if the power dissipated in the crystal is less than the drive

level with RLIM shorted, then a zero value for RLIM can be used.

As a starting point, a suggested value for RLIM is 1.5 kΩ

14.3 Power Supply Ripple Rejection

In practical system applications, power supply noise (ripple)

can be generated from switching power supplies, digital

ASICs or FPGAs, etc. While power supply bypassing will help

filter out some of this noise, it is important to understand the

effect of power supply ripple on the device performance.

When a single-tone sinusoidal signal is applied to the power

supply of a clock distribution device, such as LMK00101, it

can produce narrow-band phase modulation as well as am-

plitude modulation on the clock output (carrier). In the single-

side band phase noise spectrum, the ripple-induced phase

modulation appears as a phase spur level relative to the car-

rier (measured in dBc).

For the LMK00101, power supply ripple rejection (PSRR),

was measured as the single-sideband phase spur level (in

dBc) modulated onto the clock output when a ripple signal

was injected onto the Vddo supply. The PSRR test setup is

shown in Figure 9.

30146940

FIGURE 9. PSRR Test Setup

A signal generator was used to inject a sinusoidal signal onto

the Vddo supply of the DUT board, and the peak-to-peak ripple

amplitude was measured at the Vddo pins of the device. A lim-

iting amplifier was used to remove amplitude modulation on

the differential output clock and convert it to a single-ended

signal for the phase noise analyzer. The phase spur level

measurements were taken for clock frequencies of 100 MHz

under the following power supply ripple conditions:

•Ripple amplitude: 100 mVpp on Vddo = 2.5 V

•Ripple frequency: 100 kHz

Assuming no amplitude modulation effects and small index

modulation, the peak-to-peak deterministic jitter (DJ) can be

calculated using the measured single-sideband phase spur

level (PSRR) as follows:

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

DJ (ps pk-pk) = [(2 * 10(PSRR/20)) / (π * fclk)] * 1012 (5)

14.4 Power Supply Bypassing

The Vdd and Vddo power supplies should have a high frequen-

cy bypass capacitor, such as 100 pF, placed very close to

each supply pin. Placing the bypass capacitors on the same

layer as the LMK00101 improves input sensitivity and perfor-

mance. All bypass and decoupling capacitors should have

short connections to the supply and ground plane through a

short trace or via to minimize series inductance.

14.5 Thermal Management

For reliability and performance reasons the die temperature

should be limited to a maximum of 125 °C. That is, as an es-

timate, TA (ambient temperature) plus device power con-

sumption times θJA should not exceed 125 °C.

The package of the device has an exposed pad that provides

the primary heat removal path as well as excellent electrical

grounding to a printed circuit board. To maximize the removal

of heat from the package a thermal land pattern including

multiple vias to a ground plane must be incorporated on the

PCB within the footprint of the package. The exposed pad

must be soldered down to ensure adequate heat conduction

out of the package.

A recommended land and via pattern is shown in Figure 10.

More information on soldering LLP packages and gerber foot-

prints can be obtained: http://www.national.com/en/packag-

ing/index.html.

A recommended footprint including recommended solder

mask and solder paste layers can be found at: http://

www.national.com/en/packaging/gerber.html for the

SQA32A package.

To minimize junction temperature it is recommended that a

simple heat sink be built into the PCB (if the ground plane

layer is not exposed). This is done by including a copper area

of about 2 square inches on the opposite side of the PCB from

the device. This copper area may be plated or solder coated

to prevent corrosion but should not have conformal coating (if

possible), which could provide thermal insulation. The vias

shown in Figure 10 should connect these top and bottom

copper layers and to the ground layer. These vias act as “heat

pipes” to carry the thermal energy away from the device side

of the board to where it can be more effectively dissipated.

30146973

FIGURE 10. Recommended Land and Via Pattern

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LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

15.0 Physical Dimensions inches (millimeters) unless otherwise noted

Leadless Leadframe Package (Bottom View)

32 Pin LLP Package

16.0 Ordering Information

Order Number Package Marking Packaging

LMK00101SQX

K00101

2500 Unit Tape and Reel

LMK00101SQ 1000 Unit Tape and Reel

LMK00101SQE 250 Unit Tape and Reel

www.ti.com 12

LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

Notes

13 www.ti.com

LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

Notes

LMK00101 Ultra-low Jitter LVCMOS Fanout Buffer/Level Translator with Universal Input

www.ti.com

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