Texas Instruments LMX2531-xxxx User manual

LMX2531-xxxx Evaluation Board
User's Guide
November 2013
SNAU077A

2SNAU077A LMX2531-xxxx Evaluation Board User’s Guide November 2013
Copyright © 2013, Texas Instruments Incorporated
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LMX2531-xxxx
High Performance Frequency Synthesizer System with Integrated VCO
Evaluation Board Operating Instructions

November 2013 LMX2531-xxxx Evaluation Board User’s Guide SNAU077A 3
Copyright © 2013, Texas Instruments Incorporated
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TABLE OF CONTENTS
EQUIPMENT..................................................................................................................................................................................4
BASIC OPERATION.......................................................................................................................................................................5
LMX2531-XXXX BOARD INFORMATION......................................................................................................................................7
APPENDIX A: SCHEMATICS.........................................................................................................................................................27
APPENDIX B: BUILD DIAGRAM...................................................................................................................................................28
APPENDIX C: QUICK START ON EVM COMMUNICATION ...........................................................................................................30

4SNAU077A LMX2531-xxxx Evaluation Board User’s Guide November 2013
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Equipment
Power Supply
The Power Supply should be a low noise power supply. An Agilent 6623A Triple power supply with LC filters on the
output to reduce noise was used in creating these evaluation board instructions.
Signal Generator
The Signal Generator should be capable of frequencies and power level required for the part. A Rohde & Schwarz SML03
was used in creating these evaluation board instructions.
Phase Noise / Spectrum Analyzer
For measuring phase noise an Agilent E5052A is recommended. An Agilent E4445A PSA Spectrum Analyzer with the
Phase Noise option is also usable although the architecture of the E5052A is superior for phase noise measurements. At
frequencies less than 100 MHz the local oscillator noise of the PSA is too high and measurements will be of the local
oscillator, not the device under test.
Oscilloscope
The oscilloscope and probes should be capable of measuring the output frequencies of interest when evaluating this
board. The Agilent Infiniium DSO81204A was used in creating these evaluation board instructions.

November 2013 LMX2531-xxxx Evaluation Board User’s Guide SNAU077A 5
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Basic Operation
1. Connect the signal generator output to the OSCin input of the board. For this example we use a 10 MHz sin
signal at +5dBm power level.
2. Connect a low noise 3.3 V power supply to the Vcc connector located at the top left of the board.
3. Please see Appendix D for quick start on interfacing the board. Connect PC to the uWire header.
Laptop or PC
Laptop or PC
Power
Supply Power
Cable
Power
Cable
3.0 V
Sig Gen
SMA
cable
SMA
cable
1
3Please see
Appendix D for
interface info
Please see
Appendix D for
interface info
2OSCin
Vcc
uWire
header
10 MHz @
+5 dBm
4. Start CodeLoader4.exe.
5. Select USB or LPT Communication Mode on the Port Setup tab as appropriate.
Appendix C for

6SNAU077A LMX2531-xxxx Evaluation Board User’s Guide November 2013
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6. Click “Select Device” “PLL-VCO” LMX2531xxxx depending on which chip is on your board.
7. Check your window with “PLL/VCO” Tab screenshot, 10 MHz input, but with VCO output will be different
depending on which LMX2531xxxx you selected

November 2013 LMX2531-xxxx Evaluation Board User’s Guide SNAU077A 7
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LMX2531-xxxx Board Information
RF LOOP FILTER
Phase Margin
42.5 deg
100 uA
Loop Bandwidth
4.1 kHz
Fcomp
2.5 MHz
TCXO Frequency
10 MHz
Output Frequency
1712 –1772 MHz
VCO Gain
7.9-84.7i kHz
Supply Voltage
2.7 Volts
VCO
CPout
47 pF
2.7 nF
47 K
100 pF 100 pF
40 K40 K
Vtune

8SNAU077A LMX2531-xxxx Evaluation Board User’s Guide November 2013
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LMX2531-xxxx

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10 SNAU077A LMX2531-xxxx Evaluation Board User’s Guide November 2013
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