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Revised – March 2014

LMX248x Evaluation Board User’s Guide

SNAU137

23

Copyright © 2014, Texas Instruments Incorporated

IF PLL Spurs

Fout = 2100 MHz

Not only are the spurs below the noise, but

they are actually improving the phase noise

near the offset of the spur!

This cusping effect is due to discrete sampling

effects of the phase detector/charge pump that

occur if the loop bandwidth is wide relative to

the comparison frequency.

Fout = 2150 MHz

Spurs at 200 kHz output frequency are

–82 dBc, although the noise is still being pulled

down due to this cusping effect.

Fout = 2200 MHz

Spurs at 200 kHz are not there and actually

reducing the noise due to discrete sampling

effects.

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Summary of Contents for LMX248 Series

Page 1: ...LMX248x Evaluation Board User s Guide Revised March 2014 SNAU137 ...

Page 2: ...www ti com 2 SNAU137 LMX248x Evaluation Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated LMX248x Evaluation Board Operating Instructions ...

Page 3: ...F PLL LOCK TIME 14 IF PLL PHASE NOISE 15 IF PLL SPURS 16 LMX2486 BOARD INFORMATION 17 RF PLL PHASE NOISE 18 RF PLL FRACTIONAL SPURS 20 RF PLL LOCK TIME WITH A SPECTURM ANALYZER 21 IF PLL PHASE NOISE 22 IF PLL SPURS 23 IF PLL LOCK TIME 24 LMX2487 BOARD INFORMATION 25 FINDING A VCO 25 REPLACING THE VCO WITH A FOOTPRINT COMPATIBLE VCO 26 APPENDIX A SCHEMATICS 27 APPENDIX B BUILD DIAGRAMS 28 APPENDIX ...

Page 4: ...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...

Page 5: ...in 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 4 Start CodeLoader4 exe 5 Click Select Device PLL Fractional LMX248x depending on which chip is on your board ...

Page 6: ...LMX248x Evaluation Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated 6 Select USB or LPT Communication Mode on the Port Setup tab as appropriate 7 Click CTRL L to load settings into device ...

Page 7: ...dled with the evaluation board for connecting to a PC through the parallel printer port By means of USB2ANY uWire serial port emulation the CodeLoader software included can be run on a PC to facilitate the LMX2485 internal register programming for the evaluation and measurement RF LOOP FILTER Theoretical NOT Measured Simulation Done with EasyPLL at http www ti com lsds ti wireless Phase Margin 48 ...

Page 8: ... ti com Phase Margin 47 1 deg Lock Time 760 780 MHz MHz to 1 KHz tolerance in 453 uS Loop Bandwidth 5 1 KHz Spur Gain 200 KHz 22 1 dB VCO CPoRF 1 8 nF 10 nF 8 2 KΩ Open Open 0 Ω 0 Ω Settings for Operation Kφ 4 mA Comparison Frequency 50 kHz Output Frequency 760 780 MHz PLL Supply 2 5 Volts VCO Supply 3 Volts Other Information VCO Used VARIL191 773U VCO Gain 18 MHz Volt VCO Input Capacitance 100 pF...

Page 9: ...se Loop Bandwidth is about 10 kHz Note that the phase noise gradually improves as one goes farther from the carrier Also note that this is done with 200 uA of current and the true phase noise capability of the part is not shown here because the phase noise is worse and the VCO phase noise could still be degrading the in band phase noise ...

Page 10: ...0 uA This improves the PLL phase noise performance and also increases the loop bandwidth so the true PLL performance can be seen The reason that the original loop filter was not designed for 1600 uA current was that it makes the loop filter capacitors 8X larger and also the lower current allows one to experiment with lower comparison frequencies like 2 5 MHz 5 MHz and 10 MHz ...

Page 11: ...uency the primary fractional spur at 200 kHz is 70 7 dBc and the sub fractional spur at 100 kHz is 69 5 dBc At 2440 2 MHz output frequency the primary fractional spur at 200 kHz is 78 9 dBc and the sub fractional spur at 100 kHz is 72 9 dBc At 2480 2 MHz output frequency the primary fractional spur at 200 kHz is 80 8 dBc and the sub fractional spur at 100 kHz is 73 4 dBc ...

Page 12: ...de Revised March 2014 Copyright 2014 Texas Instruments Incorporated RFPLLLockTime No CSRC RF_TOC 0 Peak time without cycle slip reduction is 1110 uS Peak time without cycle slip reduction is 1622 uS Positive lock time is 1220 uS Negative Lock time is 1711 uS ...

Page 13: ...uide SNAU137 13 Copyright 2014 Texas Instruments Incorporated RFPLLLockTime Cycle Slip Reduction Enabled RF_TOC 500 Peak time with cycle slip reduction is 222 uS Peak time with cycle slip reduction is 222 uS Positive lock time is 345 uS Negative Lock time is 378 uS ...

Page 14: ...37 LMX248x Evaluation Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated IFPLLLockTime Peak time is 97 8 uS Peak Time is 133 3 uS Positive Lock time is 510 uS Negative Lock Time is 474 uS ...

Page 15: ...www ti com Revised March 2014 LMX248x Evaluation Board User s Guide SNAU137 15 Copyright 2014 Texas Instruments Incorporated IFPLLPhaseNoise ...

Page 16: ...an output frequency of 760 MHz are 97 5 dBc Note the cusping effect at 50 kHz This is because the loop bandwidth is wide relative to the comparison frequency This is due to the discrete sampling action of the phase detector Spurs at 50 kHz offset for an output frequency of 770 MHz are 81 7 dBc Spurs at 50 kHz offset for an output frequency of 780 MHz are 71 7 dBc ...

Page 17: ...l port emulation the CodeLoader software included can be run on a PC to facilitate the LMX2486 internal register programming for the evaluation and measurement RF Loop Filter Phase Margin 46 5 deg Pole Ratio T3 4 5 Loop Bandwidth 9 8 KHz Pole Ratio T4 T3 57 7 Theoretical Discrete Lock Time 915 uS w o CSR to 1 kHz Roll Off 200 KHz 42 7 dB VCO CPoRF 6 8 nF 220 nF 150 Ω 4 7 nF 15 nF 56 Ω 33 Ω Setting...

Page 18: ...t 2014 Texas Instruments Incorporated VCO Used VARIL190 KVCO 80 MHz Volt Input Capacitance 120 pF RFPLLPhaseNoise Loop Bandwidth is about 10 kHz Note that the phase noise gradually improves as one goes farther from the carrier This was taken with the IF PLL powered up and IF VCO connected ...

Page 19: ... com Revised March 2014 LMX248x Evaluation Board User s Guide SNAU137 19 Copyright 2014 Texas Instruments Incorporated For this plot the charge pump was increased to 16X and the other conditions were the same ...

Page 20: ...e primary fractional spur at 200 kHz is 80 dBc and the sub fractional spur at 100 kHz is below the noise floor At 3240 2 MHz output frequency the primary fractional spur at 200 kHz is 88 dBc and the sub fractional spur at 100 kHz is below the noise floor At 3200 2 MHz output frequency the primary fractional spur at 200 kHz is 82 dBc and the sub fractional spur is below the noise ...

Page 21: ... lock time measurement 3 mS in this case The power is 9 6 dBm Now tune the PLL slightly off frequency If the PLL is tuned 10 kHz off frequency the output power drops to 11 1 dBm So when the output power is 11 1 dBm or higher we are theoretically within 10 kHz If the PLL can not be tuned to fine enough resolution the center frequency of the spectrum analyzer can also be offset Using the external tr...

Page 22: ...on Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated IFPLLPhaseNoise Above is the IF PLL phase noise with the RF PLL powered up The above plot was taken with the RF PLL powered down and IF VCO disconnected ...

Page 23: ... near the offset of the spur This cusping effect is due to discrete sampling effects of the phase detector charge pump that occur if the loop bandwidth is wide relative to the comparison frequency Fout 2150 MHz Spurs at 200 kHz output frequency are 82 dBc although the noise is still being pulled down due to this cusping effect Fout 2200 MHz Spurs at 200 kHz are not there and actually reducing the ...

Page 24: ...pyright 2014 Texas Instruments Incorporated IFPLLLockTime Peak time is 73 3 uS This peak time is increased because the VCO tuning voltage is approaching the rail of the charge pump when the PLL overshoots Peak Time is 37 8 uS Positive Lock time is 253 uS Negative Lock Time is 249 uS ...

Page 25: ...X2487E it is the same part just tested to different specifications The reason that the LMX2487E sells at a premium is that it requires a special test setup for high frequency and the yields are a little lower Therefore even though the LMX2487 is being run above it s specified limits it has a high probability of working at these higher frequencies the performance is just not guaranteed FindingaVCO ...

Page 26: ...ibleVCO In order to replace the VCO take component U2 and replace with the desired VCO The VCO must be of the VARIL T style footprint which is used by manufactures like Sirenza Minicurcuits Universal Microwave and Zcomm However it is suggested that if an LMX2487 board is being modified the setup for that should be verified The dot signifies the tuning voltage ...

Page 27: ...www ti com Revised March 2014 LMX248x Evaluation Board User s Guide SNAU137 27 Copyright 2014 Texas Instruments Incorporated AppendixA Schematics LMX2487 ...

Page 28: ...www ti com 28 SNAU137 LMX248x Evaluation Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated AppendixB BuildDiagrams LMX2485 ...

Page 29: ...www ti com Revised March 2014 LMX248x Evaluation Board User s Guide SNAU137 29 Copyright 2014 Texas Instruments Incorporated LMX2486 ...

Page 30: ...www ti com 30 SNAU137 LMX248x Evaluation Board User s Guide Revised March 2014 Copyright 2014 Texas Instruments Incorporated LMX2487 ...

Page 31: ...5 50 V 5 C0G C3_RF 11 1 Kemet C0805C182J3GAC 1 8 nF 805 25 V 5 C0G C1_IF 12 1 Panasonic ECHU1C103JX5 10 nF 805 16 V 5 Film C2_IF 13 1 Kemet C0805C272J3GACTU 2 7 nF 603 C1_RF 14 2 Kemet C0603C104K3RAC 100 nF 603 25 V 10 X7R C20 C21 15 1 Panasonic ECHU1C473JB5 47 nF 1206 50 5 Film C2pRF 16 11 Kemet C0603C105K3PAC 1 uF 603 25 V 10 X5R C4 C5 C6 C7 C8 C9 C10 C11 C24 C25 C26 17 3 Kemet T494A106K010AS 10...

Page 32: ...03C682J3RAC 6 8 nF 603 25 V 5 X7R C1_RF 12 1 Kemet C1206C472J5GAC 4 7 nF 1206 50 V 5 C0G C2pIF 13 1 Kemet C0603C153J3RAC 15 nF 603 25 V 5 X7R C4_RF 14 1 Kemet C1206C103J3GAC 10 nF 1206 25 V 5 C0G C32 15 2 Kemet C0603C104K3RAC 100 nF 603 25 V 10 X7R C20 C21 16 1 Kemet C0805C224J4RAC 220 nF 805 16 V 5 X7R C2_RF 17 13 Kemet C0603C105K4PAC 1 uF 603 16 V 10 X5R C3 C4 C5 C6 C7 C8 C9 C10 C11 C24 C25 C26 ...

Page 33: ...C0603C181J5GAC 180 pF 0603 50 V 5 C0G C3_RF 11 1 Kemet C0603C681J3GAC 680 pF 0603 25 V 5 C0G C1_IF 12 1 Kemet C0805C472K3RAC 4 7 nF 0805 16 V 5 X7R C2_IF 13 1 Kemet C0603C102J5GAC 1 nF 0603 25 V 5 C0G C1_RF 14 2 Kemet C0603C104K3RAC 100 nF 0603 25 V 10 X7R C20 C21 15 1 Kemet C0805C183K3RAC 18 nF 1206 16 V 20 X7R C2pRF 16 11 Kemet C0603C105K3PAC 1 uF 0603 25 V 10 X5R C4 C5 C6 C7 C8 C9 C10 C11 C24 C...

Page 34: ...the software used to communicate with the EVM Please download the latest version from TI com http www ti com tool codeloader This EVM can be controlled through the uWire interface on board There are two options in communicating with the uWire interface from the computer OPTION 1 Open Codeloader exe Click Select Device Click Port Setup tab Click LPT in Communication Mode OPTION 2 ...

Page 35: ...x A0 C1 E5 F1 G1 H1 SYNC pin 7 LMK02000 A0 C1 E5 F1 G1 H1 SYNC pin 7 LMK0480x A0 B2 C3 E5 F0 G0 H1 Status_CLKin1 pin 3 LMK04816 4906 A0 B2 C3 E5 F0 G0 H1 Status_CLKin1 pin 3 LMK01801 A0 B4 C5 E2 F0 G0 H1 Test pin 3 SYNC0 pin 10 LMK0482x prelease A0 B5 C3 D2 E4 F0 G0 H1 CLKin1_SEL pin 6 Reset pin 10 LMX2531 A0 E5 F2 G1 H2 Trigger pin 1 LMX2485 7 A0 C1 E5 F2 G1 H0 ENOSC pin 7 CE pin 10 LMK03200 A0 E...

Page 36: ...esponsible for compliance with all legal regulatory and safety related requirements concerning its products and any use of TI components in its applications notwithstanding any applications related information or support that may be provided by TI Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failur...

Page 37: ...Mouser Electronics Authorized Distributor Click to View Pricing Inventory Delivery Lifecycle Information Texas Instruments LMX2487E EVM LMX2485E EVAL NOPB ...

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