LMX2531LQ1146E
Evaluation Board Operating Instructions
National Semiconductor Corporation
Timing Devices Business Group
10333 North Meridian
Suite 400
Indianapolis, IN 46290
LMX2531LQ1146EFPEB Rev 3.31.2008
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Table of Contents
TABLE OF CONTENTS ...................................................................................................................... 2
LOOP FILTER .................................................................................................................................. 3
QUICK SETUP ................................................................................................................................. 3
TROUBLESHOOTING ........................................................................................................................ 4
PHASE NOISE ................................................................................................................................. 5
FREE-RUNNING VCO PHASE NOISE (INTERNAL DIVIDE BY 2 DISABLED)............................................ 6
FREE-RUNNING VCO PHASE NOISE (INTERNAL DIVIDE BY 2 ENABLED)............................................. 7
FRACTIONAL SPURS (INTERNAL DIVIDE BY 2 DISABLED).................................................................... 8
FRACTIONAL SPURS (INTERNAL DIVIDE BY 2 ENABLED)..................................................................... 9
INTEGER SPURS (INTERNAL DIVIDE BY 2 DISABLED)........................................................................ 10
INTEGER SPURS (INTERNAL DIVIDE BY 2 ENABLED)........................................................................ 11
CODELOADER SETTINGS ............................................................................................................... 12
SCHEMATIC .................................................................................................................................. 17
BILL OF MATERIALS ....................................................................................................................... 18
TOP LAYER ................................................................................................................................... 19
MID LAYER 1 "GROUND PLANE"..................................................................................................... 20
MID LAYER 2 "POWER".................................................................................................................. 21
BOTTOM LAYER "SIGNAL".............................................................................................................. 22
TOP BUILD DIAGRAM ..................................................................................................................... 23
2
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Loop Filter
Loop Bandwidth 7.9 Kφ 1440 uA (16X)
Phase Margin 61.4 Fcomp 10 MHz
Crystal Frequency 10 MHz Output Frequency 1106 - 1184 MHz (DIV2=0)
553 - 592 MHz (DIV2=1)
Supply Voltage 3.0 Volts VCO Gain 2.5-5.5 MHz/Volt
VCO
CPout
open
100 nF
1KΩ
100 pF 100 pF
20 KΩ20 KΩ
Vtune
Quick Setup
• Install the CodeLoader software which is available at www.national.com/timing.
• Attach the parallel , or USB to parallel, port cable to the computer and the evaluation board.
• Connect 3.0 volts to the Vcc connector
• Connect the Fout connector to a spectrum analyzer or phase noise analyzer
• Connect a clean 10 MHz source to the OSCin pin. Typically, the 10 MHz output from the back
of the RF test equipment is a good source. Signal generators tend to be very noisy and should
be used with caution. If a signal generator is used, the signal generator phase noise
contribution can be reduced by setting the signal to 80 MHz and dividing this down to a phase
detector frequency of 10 MHz.
• Set up the CodeLoader software
o Select the proper part from the menu as Select Part->PLL+VCO->LMX2531LQ1146E
o Select the proper mode from the Mode menu
o Load the part by pressing Ctrl+L or selecting Keyboard Controls->Load Device from
the menu
• It is recommended to ensure proper communication with the device
o Click the REG_RST bit on the bits/pins page and observe the current go to 0 mA
o Unclick the REG_RST bit AND press Ctrl+L. The current should be approximately
35 mA
o If device does not respond to this, consult the troubleshooting section
• When using the lower frequency band with divide by 2 enabled (DIV2=1), be aware that the
frequency programmed to the VCO is actually twice the output frequency of the device
because the VCO frequency is being divided by 2.
3
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Troubleshooting
Problem Corrective Actions
Software does not communicate with the evaluation boards
All Modes
• Ensure a valid signal is presented to the OSCin connector. If a signal generator
is used, ensure the RF is ON.
• Consult the CodeLoader instructions for more detailed information on
communication issues
LPT Mode (Uses Parallel Port Cable)
• Ensure that CodeLoader is selected to LPT mode on the Port Setup tab
• Ensure the proper port number is selected (LPT1, LPT2, LPT3). CodeLoader
does NOT automatically detect this.
• Ensure the LPT cable is securely connected to the computer and board.
• Exit and Restart CodeLoader
• Ensure the parallel port is in the correct mode
o Windows often requires Administrative access to write to the parallel
port
o Ensure that the parallel port is set to “Enabled” in windows device
manager
o A reboot upon installation of CodeLoader is sometimes necessary to get
the parallel port to work.
o Standard mode is the most reliable. This can be set in the BIOS mode
of the computer as “Normal”, “Output Only”, or “AT”
USB Mode (Uses USB to Parallel Port Converter)
• On the menu, select USB->Version to verify communication with the board
• Ensure the Green LEDs are lit on the USB board
• Ensure there are no conflicts with other USB devices and reinstall the board
Part responds to
programming, but
does not lock to the
correct frequency
• Ensure that there is a valid signal presented to the OSCin connector. If a signal
generator is used, ensure that the RF is set to ON.
• If using the lower frequency band (DIV2=1), the VCO frequency in CodeLoader
should be twice the frequency at the Fout pin.
• Ensure that the VCO FREQUENCY CAL bits on the Bits/Pins tab are correct
• Ensure that the loop filter is optimized if the charge pump current, phase detector
frequency, or loop filter values have been changed from their original settings.
Ensure that the integrated loop filter components on CodeLoader are set to their
proper settings
Cl
no
ose-in phase
ise is worse
than evaluation
board
instructions show
• Ensure the signal presented to OSCin connector is clean. Try another source,
or if it is a signal generator, try using a higher frequency and dividing it down to
the phase detector frequency.
• Ensure the OSCin signal and cable provide sufficient power level.
• If the phase detector frequency or charge pump current are lowered from their
original settings, the in-band phase noise can be degraded, even if the loop filter
is re-designed for the same loop bandwidth. If the loop bandwidth is decreased,
in-band phase noise can be degraded
Far-out Phase
noise is worse
than evaluation
board
instructions show
• Ensure the measurement equipment noise floor is not limiting the measurement.
For spectrum analyzers, the noise floor at a particular setting can be measured
by removing the RF input signal
• If the settings are changed from what the board was designed for, ensure the
delta-sigma modulator is not increasing the far-out noise. To know this, tune to
an integer channel and set the ORDER bit to “Reset Modulator”. The far out
phase noise should not decrease. If it does, try a loop filter with more
attenuation or select a lower order delta-sigma modulator.
4
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Phase Noise
Output Frequency = 1146 MHz
Internal Divide by 2 Disabled (DIV2=0)
Output Frequency = 573 MHz
Internal Divide by 2 Enabled (DIV2=1)
5
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Free-Running VCO Phase Noise (Internal Divide by 2 Disabled)
Fout = 1106 MHz
Fout = 1146 MHz
Fout = 1184 MHz
The plots to the left show the true phase noise capability of the
VCO. In order to take these plots, the E5052 phase nose
analyzer was used. The method was to lock the PLL to the
proper frequency, then disable the EN_PLL, EN_PLLLDO1, and
EN_PLLLDO2 bits. The equipment needs to be able to track
the VCO phase noise to measure in this way, and one can not
let the VCO drift too far off in frequency. If this kind of equipment
is not available, the VCO phase noise can also be measured by
making a very narrow loop bandwidth filter.
6
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Free-Running VCO Phase Noise (Internal Divide by 2 Enabled)
Fout = 553 MHz (1106 MHz/2)
Fout = 573 MHz (1146 MHz/2)
Fout = 592 MHz (1184 Mhz/2)
The plots to the left show the true phase noise capability of the
VCO. In order to take these plots, the E5052 phase nose
analyzer was used. The method was to lock the PLL to the
proper frequency, then disable the EN_PLL, EN_PLLLDO1, and
EN_PLLLDO2 bits. The equipment needs to be able to track
the VCO phase noise to measure in this way, and one can not
let the VCO drift too far off in frequency. If this kind of equipment
is not available, the VCO phase noise can also be measured by
making a very narrow loop bandwidth filter.
When divide by 2 is enabled, the phase noise at lower offsets is
about 6 dB better; but at high offsets, the phase noise
improvement may be less because the divider is noise floor is
adding to the phase noise.
7
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Fractional Spurs (Internal Divide by 2 Disabled)
Fractional Spur at 250 kHz offset at a
worst case frequency of 1110.25 MHz is
–78.6 dBc. Worst case channels occur
at exactly one channel spacing above or
below a multiple of the crystal frequency.
Fractional Spur at 250 kHz offset at a
worst case frequency of 1150.25 MHz is
–73.3 dBc. The sub-fractional spur at
125 kHz offset of -81.3 dBc is also
visible
Fractional Spur at 250 kHz offset at a
worst case frequency of 1180.25 MHz is
– 76.4 dBc.
8
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Fractional Spurs (Internal Divide by 2 Enabled)
Spur at 250 kHz offset at a frequency of
555.125 MHz is –92.5 dBc. Since this
mode uses the divide by 2 mode, the
channel spacing here is actually 125
kHz. The spur at 125 kHz could be
completely eliminated changing the
fractional denominator.
Spur at 250 kHz offset for a frequency of
575.125 MHz is -83.4 dBc.
Spur at 250 kHz offset for a frequency of
590.125 MHz is –83.6 dBc.
9
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Integer Spurs (Internal Divide by 2 Disabled)
Spur at 10 MHz offset for a frequency of
1106 MHz is -94.7 dBc .
Spur at 10 MHz offset for a frequency of
1146 MHz is -93.2 dBc..
Spur at 10 MHz offset for a frequency of
1184 MHz is below the spectrum
analyzer noise floor.
10
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Integer Spurs (Internal Divide by 2 Enabled)
Spur at 10 MHz offset for a frequency of
553 MHz is below the spectrum
analyzer noise floor.
Spur at 10 MHz offset for a frequency of
573 MHz is below the spectrum
analyzer noise floor.
Spur at 10 MHz offset for a frequency of
592 MHz is below the spectrum analyzer
noise floor.
11
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
CodeLoader Settings
CodeLoader runs many devices. When CodeLoader is first started, it is
necessary to select the correct device.
12
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
There can be different modes defined for a particular part. A mode can be
recalled easily from the menu. This restores bit settings and frequencies, but not
the Port Setup information. For the CodeLoader program, the default reference
oscillator used for these instructions was 10 MHz, but there is a mode for a 61.44
MHz oscillator as well. If the bits become scrambled, their original state may be
recalled by choosing the appropriate mode. If the internal divide by 2 (DIV2) is
enabled, the VCO frequency still reflects the VCO frequency before the divide by
2.
13
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
The Bits/Pins tab displays many of the bits used to program the part. Right
mouse click any bit to view more information about what this does.
When the DIV2 bit is enabled, the frequency from the part will be half of that
shown on the PLL/VCO tab. The frequency on the PLL/VCO tab does not reflect
this because the divide by 2 is actually after the VCO. Also be sure to load the
device (Ctrl+L) after changing this bit to allow the VCO to calibrate for optimal
phase noise performance.
14
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
The Registers tab shows the literal bits that are being sent to the part. These are
the registers every time the PLL is loaded by using the menu command or Ctrl+L.
R5 (INIT1) and R5 (INIT 2) are just the R5 register being used to properly
initialize the part. So a single CNT+L will load the part.
15
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
The port setup tells CodeLoader what information goes where. If this is wrong,
the part will not program. Although LPT1 is usually correct, CodeLoader does
NOT automatically detect the correct port. On some laptops, it may be LPT3.
16
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Schematic
123456
A
B
C
D
6
54321
D
C
B
A
Title
Number RevisionSize
B
Date: 6-Jan-2006 Sheet of
File: C:\Documentum\Checkout\LMX2531LQEBPCB.ddb.ddbDrawn By:
R6
R16 R15 R13 R12 R11
R2_LF
R8
C7
C2pLF
C2_LF
C1_LF
R14
LMX2531 Eval uation Boar d
L M X2 53 1SLB CBP C B 0 1- 0 6- 2 006
Dan Chappel l
C8
1 2
3 4
5 6
7 8
910
uW IRE
R10
C6
R2pLF
C16
FRAME
Fout
Vcc
R21
R19
R20
C1
R2
C12
C2
VccVCO
VccDIG
VccPLL
VccBUF
R3
C3
C17
R4
C9
C4
R5
C5
OSCin
VccVCO
VccPLL
VccBUF
C13
C18
C20
R7
R23
R22
Ftest/ LD
C15
C22
R1
R9
TRIGGER
GND
1 2
3 4
5 6
7 8
POW ER
C24
C14
C11
C19
C21
C23
Note that Any Component wi th Desig nator 100 or Hig her i s on the Bottom Si de of the Board
C10
VccDIG
1
NC
2
GND
3
NC
4
NC
5
Vreg BUF
6
NC
7
DATA
8
CLK
9
LE
10
CE
11
NC
12
NC
13
NC
14
NC
15
VccVCO
16
VregVCO
17
VrefVCO
18
GND 19
GND 20
Fout 21
VccBUF 22
Vtune 23
CPout 24
FLout 25
VregPLL1 26
VccPLL 27
GND 34
NC 29
Ftest/LD 30
OSCin 31
OSCin* 32
Test 33
NC 35
VregDIG 36
VregPLL2 28
SLG1
37
SLG2
38
SLG3
39
U1
Vcc
Vcc
R18
R24
R17
C105
C100
C101
C103
C104
C102
VccDIG
17
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Bill of Materials
Bill of Materials LMX2531_LF Revision 3.28.2008
Item QTY Manufacturer Part # Size Tol Voltage Material Value Designators
C1_LF, C2pLF, C2, C3, C4, C5, C9,
C11, C14, C17, C18, C19, C21, C24,
20 Open Capacitors
C100, C101, C102, C103, C104, C105
7 Open Resistors R2pLF,R7, R8, R17, R19, R21, R24
0
1
n/a
Open Miscellaneous Ftest/LD
1 1 Kemet C0603C101J5GAC 603 5% 50V C0G 100pF C16
2 2 Kemet C0603C103J5RAC 603 5% 50V X7R 10nF C10, C23
3 1 Kemet C0805C104K5RACTU 805 5% 25V C0G 100nF C2_LF
4 6 Kemet C0603C104J3RAC 603 5% 25V X7R 100nF C6, C7, C12, C15, C22, C20
5 1 Kemet C0603C105K4RAC 603 10% 16V X5R 1uF C8
6 1 Kemet C0603C475K9PAC 603 10% 6.3V X5R 4.7uF C13
7 1 Kemet C0805C106K8PAC 805 10% 10V X5R 10uF C1
8 1 Vishay CRCW0603000ZRT1 603 5% 0.1W Thick Film 0Ω R20
9 2 Panasonic P.22AHCT-ND 603 10% 0.1W Thick Film 0.22Ω R22, R23
10 2 Vishay CRCW06033R3JRT1 603 5% 0.1W Thick Film 3.3Ω R1, R18
11 4 Vishay CRCW0603100JRT1 603 5% 0.1W Thick Film 10Ω R2, R3, R4, R5
12 1 Vishay CRCW0603510JRT1 603 5% 0.1W Thick Film 51Ω R6
13 1 Vishay CRCW0603102JRT1 603 5% 0.1W Thick Film 1KΩ R2_LF
14 4 Vishay CRCW0603103JRT1 603 5% 0.1W Thick Film 10KΩ R9, R11, R13, R15
15 4 Vishay CRCW0603123JRT1 603 5% 0.1W Thick Film 12KΩ R10, R12, R14, R16
16
1Comm Con
Connectors HTSM3203-8G2 2X4 n/a n/a Metal/Plastic Header POWER
17 1 FCI Electronics 52601-S10-8 2X5 n/a n/a Metal/Plastic Header uWire
18 3 Johnson Components 142-0701-851 SMA n/a n/a Metal SMA Fout, OSCin, Vcc
FR4 PCB Board
19
1National
Semiconductor LMX2531LQEBPCB n/a n/a n/a 62 mil Thick 1st Layer 10 mils n/a
20
1National
Semiconductor LMX2531 LLP36 n/a 2.7 Silicon LMX2531 U1
Place Across:
21 4 Com Con Connectors CCIJ255G 2-Pin n/a n/a Metal/Plastic Shunt POWER: 1-2, 3-4, 5-6, 7-8
22 4 SPC Technology SPCS-8 0.156" n/a n/a Nylon Nylon Standoffs Place in 4 Holes in Corners of Board
18
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Top Layer
19
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Mid Layer 1 "Ground Plane" (15 Mils Down FR4)
20
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Mid Layer 2 "Power"
21
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Bottom Layer "Signal"
Note: Total Board Thickness = 61 mils
22
LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Top Build Diagram
23
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