Voltage Regulator Test Standard
Contents
1. OMICRON IL AE LH PICOTEST www pcotstcomtw monitor AC DC Vs 112V Max Current Injector Model NO J2111A Figure 12 Output impedance connection diagram Making Measurements 21 Making Measurements Open the Bode file below to begin making the Output impedance measurement LM317 Output Z Bode Calibrate the probes using the same process as in the Bode measurement Press Run and the results should be similar to those in Figure 13 10 10 104 10 108 107 f Hz E TRA Mag Gain Figure 13 Output impedance plot of the LM317 test circuit Why is this important e Often there is either no injection point available to extract a Bode Plot from a voltage regulator or there is simply no way to measure the control loop in a case such as a fixed monolithic regulator Output impedance allows us to non invasively extract stability information while a system is on and running e Output impedance is an overall less expensive way to make a stability measurement Recommendations Insert the 22uF capacitor Capacitor 6 into either P7 or P8 on the board leaving all other connections the same as the original output impedance measurement Open the following Bode File calibrate and perform the measurement LM317 Output Z 22uF Bode Making Measurements 28 The resulting plot should be similar to those in Figure 142. a Uy PICOTEST Voltage Regulator Test Standard Test Platform for Voltage Regulator and LDO Testing E PICoTEST art M voltage Regulator Test stand perfect for Testing Bode Plots Stability Transient Load Step gt PSRR Output Impedance Reverse Transfer Input Impedance Crosstalk Version 11 MUN y Documentation Version 1 0d December 2010 O 2010 Picotest Corp All Rights Reserved Trademarks The Picotest logo and Picotest Injectors are trademarks of Picotest Corp All other brand and product names mentioned herein are used for identification purposes only and are registered trademarks trademarks or service marks of their respective holders Copyright notice Except as permitted under the United States Copyright Act of 1976 no part of this publication may be reproduced or distributed in any form or by any means or stored in a data base or retrieval system without the prior written permission of Picotest Corp Contact information Corporate offices 1 877 914 PICO Technical support e mail info Q picotest com World Wide Web http www picotest com Table of Contents Ghapter de Ucrania 5 PVC A 5 APP ee E O eet vcore eed A 6 Paris a Isi Cr sa 6 Documentation and SO DO Tecnico aae 8 IA an a IMA o oo oo e O Test Standatrd Kit CapaDillti oem sloatpyeitail EEEE EENE errr trey 9 Special nal zer SUPPO sacd
3. i 80u 20 E 60u MO o 4 c 40u ae CC 20 D L ot Je 20u 407 60 i i j 10 103 104 10 108 107 HZ mme Hi Mag GCain mmm TR2 Tg Gain Figure 14 Output impedance and group delay plot of the LM317 test circuit Using cursor 1 in the Bode software observe the peak in Group Delay or Tg measured by Trace 2 This occurs at about 27kHz and has a peak value of 94us Using this can calculate the Q at the output of the regulator as well as the phase margin of the system olos 10 527 10 7 889 Eq 1 In this case Q comes out to be 7 89 Now using Eq 2 we can calculate the phase margin of the system pulos TON 10 7 253 Eq 2 For this example we calculate a phase margin of 7 2 degrees which is in vety good agreement with the phase margin measured for the same regulator and output capacitor in the Bode Plot measurement It is also important to note that the peak of the output impedance occurs at about 27 89kHz which is the measured bandwidth of the system in this configuration using the Bode Plot measurement technique Both bandwidth and phase margin were able to be extracted from the system without needed access to the control loop or breaking any connections of the system This is a very accurate non invasive method of measuring the stability of a system Making Measurements 29 Reverse Transfer Reverse transfer is an unappreciated and rarely discussed characteristic defining the attenuation of th
4. This applies to every test Oscilloscope S wi md zn di E G5100A Arbitrary Waveform Generator amp Function Generator lt gt PICOTEST www picot st comtw monitor AC DC Vs Current Injector Model NO J2111A il E Figure 6 Step load connection diagram Making Measurements 19 Equipment Setup Insert the 22uF ceramic capacitor Capacitor 6 into P7 or P8 On the waveform generator set a 1k Hz square wave to an amplitude of 2V 20mApk pk and set the DC offset to 1 0V Set the time base on the oscilloscope to 200uS div D o A 207 xi 0 0s 200 08 Trigd Bj 665 Py O LLLI Min 3 24 06mA Max 3 44 57mA Pk Pk 1 16 4mV Figure 7 LM317 output voltage response Ch1 to load step Ch3 200us time base Note that the frequency response has two distinct frequencies indicating the sensitivity of the bandwidth to the load current This ringing is indicative of a low phase margin which is confirmed by the Bode Plot measurement Change the time base on the oscilloscope to 10uS div Min 24 34mA Max gt 44 84mA Ampl 1 15 2mV Fall lt 300ns 207 Y 20 s 5 008 10 008 Trigd PB 665 Figure 8 LM317 output voltage response Ch1 to load step Ch3 10us time base Making Measurements 20 Note the appearance of a higher frequency voltage excursion Not having a high enough resolution when looking at the step load response is one si
5. ZHL 0 20 pee 100 40 TR1 dB 102 103 104 105 108 107 t Hz meme Hi Mag Cain mmm TR2 Phase Gain Figure 5 Correct Bode plot of LM317 test circuit Signal injection level is at 45dBm Often levels below the smallest capability of the analyzer are required to yield the correct result The best way to recognize that the signal level is affecting the measurement is to run multiple sweeps at increasing lower levels until the shape of the measurement 1s no longer affected by the decreasing level Striking a balance between being below the level where we affect the measurement yet being above the noise floor is the goal Don t be afraid of a little noise at low injection levels your measurement being accurate is at stake Making Measurements 18 Transient Step Load Measurements The step load test shows the time domain response of the voltage regulator to a change in current If the current change is small signal information about the control loop can be observed The solid state current injector has a high bandwidth and fast response time in order to assure that the injector itself does not limit the measurement Equipment List e High Speed Wave Generator such as the Picotest G5100A e J2111A Current Injector e Oscilloscope e LM317 Adjustable Regulator board Connectivity Diagram Note in general you can add a jumper across the top of J1 J2 or you can connect the Picotest line Injector
6. calibrating the probes then try measuring with the current settings Notice that the current measurement does not overlay well with the saved data This is because the current measurement has too large of an oscillator signal level that it is yielding a measurement with the wrong answer In the configuration box to the left of the plot type 10 dBm into the Level field Re running the measurement you can see the results have changed from before If you continue decrease the signal level we will reach the lower limit of the Bode 100 27 dBm before we get to the correct answer The J2140 Attenuator is needed to produce a small enough oscillator injection level such that we are not affecting the measurement with the signal and can get the correct result Connect the 40dB attenuator to the output of the Bode 100 oscillator as shown in Figure 4 Making Measurements 16 10Hz 45MHz Attenuator Injection Transformer Model NO J2140A Model NO J2101A mS ce Ce a MADE N TATWAN ow We m WADE IM TANAAN Zoomed in connection view Of the ADJ board Figure 4 LM317 to Bode100 connection with the addition of the 40dB Attenuator Making Measurements 17 Now reset the signal level in the configuration box back to 5 dBm Performing the measurement with a 45dBm injection signal should now yield the correct result and the measurement should like Figure 5 60 40 400 20 Wi i o o
7. supplying at least 15V e Component 2 board SR105 T Schottky Diode Connectivity Diagram T SSS J A OUTPUT 0 8 A 3 Bode 100 25V from power supply LD PICOTEST 50Vdc Max OUT osc DC Bias Injector Component 2 Schottky Diode SR105 T Model NO J2130A CEZ X is MADE IN TAIWAN Figure 21 DC Bias Injector connections to the Bode100 and Component 2 board Data to Record Open the Bode file below to begin making the component impedance measurement Diode Z 25V Bias Bode References 36 Calibrating for an impedance measurement 1s different than a gain measurement used in the previous measurement Using the connection diagram above with the 25V applied select User Calibration and replace the component with an Open Short and 50 ohm terminations for each of the 3 calibrations Select Probe Calibration and repeat this process Connect Component 2 back onto the output of the DC Bias Injection and perform the frequency sweep Your results should be similar to those shown in Figure 22 102 103 104 105 108 107 t Hz mms 1R1 Mag Impedance Figure 22 Impedance of the SR105 T Schottky Diode Why is this important e Looking at the impedance of either passive or active components under different bias conditions and over frequency allows us to see the dynamic performance of the part e When modeling components in SPICE this met
8. Test Standard The figure shows where the Picotest Injectors Injection Transformer J2100A J2101A Current Injector J2120A and Line Injector J2130A are connected Making Measurements 4 LWS PICOTEST Voltage Regulator Test Standard Main Board OTOZ 1H9INSAdO T 04834 30123 NI Capacitor 1 100uF Tantalum z Capacitor 3 100uF Electrolytic 5 C Capacitor 5 15uF Tantalum Fixed Regulator 7 5V POWER ADAPTER TLV2217 3 3V Universal Power Supply res Regulator EH Capacitor 2 0 1uF Ceramic L Capacitor 4 2 2uF Tantalum 31 Capacitor 6 22uF Ceramic Figure 2 the structure of the Voltage Regulator Test Standard as it is laid out in the delivery box Documentation and Support The support section of Picotest s web site http www picotest com support asp contains additional documentation and various publications on testing power supplies regulators and other equipments in the Picotest Signal Injector Set Warranty Every Picotest product you buy from Picotest com is backed by a 3 year product manufacturer s warranty Making Measurements 9 Test Standard Kit Capabilities The Voltage Regulator Test Standard kit is designed to assist you in testing all types of voltage regulators and LDOs individually or as part of a distributed power system This manual presents the material in a tutorial format so that you can perform each test yourself using the connection diagrams provid
9. ard motherboard 2 gt W AW PICOTEST COM ry E i r 8 A 3g a 4 G 10 Figure 3 The Voltage Regulator Test Standard motherboard and its key connection points Input power connection AC Wall Adapter 7 5V input Input header jumper top of J1 amp J2 if J2120A Line Injector is not used Regulator 1 connection slot Texas Instruments HPA562 regulator connection slot HPA562 and others available separately Regulator 1 Output Two slots for Regulator 1 and output capacitor s Regulator 1 ground Regulator 2 output Regulator 2 ground One slot for Regulator 2 output capacitor Regulator 2 connection slot Input ground pin Input voltage pin Input current monitor 50 ohm termination E E LE MPP RPP PR PUNEO Making Measurements 11 Chapter 2 Making Measurements Connection Legend For each measurement connection diagrams are used to describe the setup of the equipment and cables used in the measurement The following legend will be used throughout this manual for more easy teadability Connection Legend Banana Cable oClipend 2 oPlug end SO oTwisted pair OBanana cable to ground pin BNC Cable 1 1 Scope Probe Ground Clip Jumper Wire SOQ Use500 termination at analyzer HighO use high impedance termination at analyzer Figure 1 The symbols used in the connection diagrams Making Measurements 12 Stability Bode Plot Measureme
10. e load current perturbations at the regulator input Typical series pass regulators are generally OdB Equipment List e Bode 100 or other network analyzer e J2111A Current Injector e LM317 Adjustable Regulator board Connectivity Diagram 500 500 OMICRON CI LAB Add a jumper across top of J1 amp J2 WWW PICOTEST COM AL LA lt gt PICOTEST www picote st com tw monitor MOD gt OUT AC DC Vs Current Injector Model NO J2111A d a LM Figure 15 Current Injector and board connections to the Bode100 Data to Record Open the Bode file below to begin making the reverse transfer measurement LM317 Reverse Transfer Bode Making Measurements 30 Calibrate the probes using the same process as in the Bode measurement Press Run and the results should be similar to those in Figure 16 102 103 104 10 108 107 f Hz mme TR1 Mag Gain Figure 16 Reverse transfer plot of the LM317 test circuit Why is this important e Current perturbations on the output of the regulator are passed back through to the input and as a result of bus impedance show up as voltage noise on the input bus Tips Consider the effect of other regulators sharing as common input When looking at the conducted susceptibility of regulators in a distributed system keep this measurement in mind as it is often the reason high frequency content i
11. ed Bench test results are also provided so you can compare your measured results The tests outlined require the following additional equipment Stability PSRR Input Output Impedance reverse transfer Test Network Analyzer Agilent 3577A OMICRON Lab Bode 100 Core Technologies Venable Ridley or similar network analyzer with the appropriate bandwidth range Step Load Test Arbitrary Waveform generator or function generator with controllable rise and fall times Picotest G5100A or similar Transient Step Load Test Oscilloscope Agilent DSO or similar Equipment Note the Picotest Signal Injectors may be used with just about any suitable network analyzer arbitrary function generator and oscilloscope Special Analyzer Support The CD in you kit includes the network analyzer measurement files for each measurement The files are compatible with the OMICRON Lab Bode 100 analyzer The measurements are saved as memory and the data display is set to memory and data This allows all of the settings to be provided for your convenience and also for you to see if your measurement results are correct The Bode 100 Software Suite is included along with the complete Bode 100 user manual where you can find detailed instructions on the analyzer s usage Making Measurements 10 Demo Board Layout The diagram below discusses how the Picotest Signal Injectors and components and load capacitors are connected to the Test Stand
12. eing drawn will result in a PERMANENTLY biased transformer Making Measurements 25 Other Recommendations Observe the frequency at which the PSRR gain curve crosses OdB Using the Line Injector connected in the same configuration as the first measurement inject a 1V peak to peak sine wave at the frequency of the zero crossing seen in the PSRR measurement from an arbitrary waveform generator such as the Picotest G5100A Connect to scope probes to the oscilloscope and put one probe on the input of the regulator and one on the output Since OdB translates to a 1 1 voltage ratio you will see the same amplitude in both sine waves on the scope Changing the sine wave to other frequencies you can confirm the results seen the PSRR gain plot by observing the attenuation ot amplification the input signal at the output of the regulator Making Measurements 26 Output Impedance Using output impedance measurements to characterize the stability of a regulator is quickly becoming a more popular alternative to using Bode plots and step load analysis Using the Current Injector to sweep current over a very large range of frequencies the output impedance can be measured and from that we can non invasively extract Q and phase margin of the system Equipment List e Bode 100 or other network analyzer e J2111A Current Injector e One 1 1 scope probe or BNC cable with a hook or clip e LM317 Adjustable Regulator board Connectivity Diagram
13. er is used to isolate the oscillator ground from the board ground This is to avoid shorting out the 2 resistor that provides the current sensing for channel 1 Making Measurements 34 Data to Record Open the Bode file below to begin making the input impedance measurement LM317 Input Z Bode Calibrate the probes using the same process as the Bode measurement Press Run and the results should be similar to those in Figure 20 10 10 104 10 108 107 f Hz memes TRA Mag Gain Figure 20 Input impedance of the LM317 test circuit Why is this important e The combined impedance of the input filter and the input of the regulator make up the criteria for Middlebrook Stability Tips e When measuring the input impedance of a system where there is no current monitor voltage a current probe works just as well as long as it is has to bandwidth to support the measurement range e When using the Line Injector on a system with a lot of input capacitance signals must be kept as small as possible as the signal capacity of the Line Injector goes down when driving capacitive loads References 35 Component Impedance Device parameters can be extracted by looking at the impedance of that device In the case of an active device a DC bias must be applied to properly measure the impedance Equipment List e Bode 100 or other network analyzer e J2130A DC Bias Injector e Power Supply capable of
14. g the PSRR measurement LM317 PSRR Bode Making Measurements 24 Calibrate the probes using the same process as in the Bode measurement Press Run and the results should be similar to those in Figure 11 TR1 dB 60 40 10 103 104 105 108 107 HZ mme TR1 Mag Gain Figure 11 PSRR of LM317 test circuit Why is this important The results are frequency dependent and the characteristics can be critical to the performance of instrumentation and RF equipment powered by the regulator Tips Where stability is a strong function of the output filter of the regulator the PSRR of a regulator is very dependent on the input filter of the regulator as well as the type of regulator used linear regulator switching regulator etc Try using different styles of input filters and use this method of measuring PSRR to quickly determine the performance of the filter Using the Line Injector for the PSRR measurement is a preferred method to many previous methods suggested by regulator manufacturers Often guides on making this measurement involve using an injection transformer to inject the input signal This is a great way to ruin an expensive transformer Since a good injection transformer uses a very high permeability core to perform well at low frequencies as a result it will saturate at as little as 10mA Using an injection transformer in line with a voltage regulator with nearly any current b
15. he bandwidth of the control loop This oscillation also appears as EMI at both the input and the output of the power supply or regulator This has all of the drawbacks associated with ripple e The control loop stability controls PSRR dynamic response and output impedance Poor stability means that all of these responses will also be poot Making Measurements 15 Tips e The 1 measurement issue is using an injection signal that is too large The signals must be very small and in some cases an attenuator is needed to reduce the oscillator signal level The Picotest J2140A provides attenuation of 10dB 70dB in 10dB steps e The stability is significantly dependent on operation conditions such as input voltage and load current so be sure to evaluate it at all operating conditions e tis possible for the loop gain to increase after crossing unity gain resulting in additional crossings so be sure that you measurement and injector are capable of measuring to a sufficient frequency e Often circuit loads include decoupling capacitors and filters that can destabilize the control loop Be sure to include them in your measurements e Use of audio transformers or video transformers is not recommended and they will often provide incorrect results Recommendations Insert the 22uF ceramic capacitor Capacitor 6 into P7 or P8 Repeat the measurement using the following Bode 100 file LM317 Bode 22uF 45dB Bode Repeat the steps for
16. hod gives us a way to extract a device s parameters very accurately thus making for a more accurate model Tips e The signal level must be kept as low as possible when measuring an active device Too high of an injection will result in changing the measured impedance of the junction leading to VERY incorrect measurements References 37 Chapter 3 References General 1 Switchmode Power Supply Simulation with PSpice and SPICE 3 by Steven M Sandler McGraw Hill Professional 1 edition 2006 ISBN 0071463267 Switch Mode Power Supply SPICE Cookbook by Christophe P Basso McGraw Hill Professional 1 edition March 19 2001 ISBN 0071375090 Power Specialist s App Note Book Papers on Simulation Modeling and More Edited by Charles Hymowitz http www intusoft com lit psbook zip Inline equations offer hysteresis switch in PSpice Christophe Basso On Semiconductor EDN August 16 2001 SPICE Circuit Handbook by Steven M Sandler and Charles E Hymowitz McGraw Hill Professional 1 edition 2006 ISBN 0071468579
17. llowing Bode 100 file LM317 Stability Bode Making Measurements 14 Under the calibration menu select PROBE calibration and choose the THRU calibration This calibration will adjust for the differences in frequency response of the two probes For additional details and methods about calibration see Calibrating the Bode 100 in the Bode 100 user manual Making the Measurement With the BODE 100 calibrated move the probe connected to CH1 of the analyzer to pin 3 of the ADJ board You should see measured bode response with solid lines and the provided result with dashed lines If your plot is upside down switch the position of the two probes If you switch the probes at the Bode 100 you will need to repeat the calibration above The resulting Bode plot should look similar to Figure 3 60 i 40 100 an i O 20 3 Cr 0 o ll lam 20 100 40 Hi 10 109 104 109 106 107 f Hz mm Hi Mag GCain mmm TR2 Phase Gain Figure 3 Bode Plot of LM317 test circuit Note the circuit has high bandwidth and great phase margin but higher frequencies indicate areas of instability and will cause output voltage oscillations seen in the time domain Why is this important e The stability of a control loop determines the closed loop performance of many aspects of the device e Anunstable power supply can oscillate resulting in very large apparent ripple at t
18. mple way to get the incorrect result Now change the time base on the oscilloscope to 200nS div Note the change in the apparent voltage excursion It is now very apparent that there is a high frequency voltage spike that is actually higher in amplitude than the original ringing seen when at a larger time base 208 B 207 ge 5008 200 027 Tia Y A Ete Min y 20 86mA Max 44 77mA Ampl 1 40 1mY Figure 9 LM317 output voltage response Ch1 to load step Ch3 200ns time base Changing the rise fall time of the square wave to slower rate as seen with slower electronic load rise fall times will result in a change in the voltage excursion This is a second simple way to get an incorrect result Making Measurements 21 Why is this important Tips Under dynamic loading conditions the voltages can go far below and above the DC regulation limits This can cause damage to the loads The dynamic voltage response can have similar effects to ripple including degrading SNR BER phase noise jitter etc The solid state current injector is a small signal injector allowing observation of the control loop performance It is not to be confused with an electronic load An electronic load is generally not useful for this test especially if small output capacitors are used The electronic load has low current rise and fall times as well as low operating bandwidth compared with the solid state current injector There are two respo
19. necuvity DIAM M M 29 b dandi canas PPP ere 30 ji m m 30 A E 31 Connect ere 31 PrO R O a a et ona ioca E O A IA aS 32 AN Bv AS thiscttfiDO PE eani AA AAA A au pue aca 52 Input Impedancia ioc s 33 Edtipment lista Em 33 Connectivite BiU iar P NE ME EE 59 Dita to Recorra odo e Ast au n 34 Way ls this portan Eusimalua e dolida adas 34 ERRE RN 34 Component impedancias n3 Be UN he oat eimi ius T 35 COME CA AA Saa 35 Darto Records RTT 35 ADT 159 63Is JH DOPCO BE nd a a a A 36 AE E E A N A UR T RA 36 Chapter S References T A E E 37 Eso A II A A A 97 Making Measurements Chapter 1 Overview Welcome Thank you for purchasing the Voltage Regulator Test Standard kit from Picotest The kit is designed to ease testing of voltage regulators LDO and other type of three terminal regulators With the kit you can perform many different types of tests Stability PSRR Transient Load Step Crosstalk Reverse Transfer Output Impedance Input Impedance Component Impedance Summary of Benefits Easily compare the performance of different regulators Easily perform a series of characterization measurements like PSRR Reverse Transfer Stability and Output Impedance on a particular regulator circuit configuration Easily swap load capacitance to investigate the impact on your
20. nses the natural response which occurs when the load change occurs at a rate much lower than the bandwidth of the regulator and the forced response which occurs when the load change is at the bandwidth of the regulator It is possible and quite easy in fact to obtain incorrect results from the load step testing The oscilloscope and probe must have adequate bandwidth and sampling rate The time base must also be consistent with the measurement Making Measurements 22 PSRR Measurements PSRR or Power Supply Rejection Ratio is the measure of the conducted susceptibility of a regulator In short this is a measure of how much of an AC signal is attenuated from the input to the output In this measurement we inject an AC signal into the input of the regulator using the J2120A Line Injector and measure input voltage into CH2 over output voltage into CH 1 Equipment List e Bode 100 or other network analyzer e J2111A Current Injector e J2120A Line Injector e Two 1 1 scope probes or BNC cables with hooks or clips e LM317 Adjustable Regulator board Making Measurements 23 Connectivity Diagram Line Injector Model NO J2120A Ce X WWW PICOTEST COM lt gt PICOTEST www picot st com tw pa i x monitor OUT AC DC Vs 12V Max Current Injector Model NO J2111A Figure 10 PSRR connection diagram Making the measurement Open the Bode file below to begin makin
21. nts The Bode plot is the generally accepted method for assessing the stability of a voltage regulator control loop The LM317 adjustable regulator board is used to demonstrate this test While this is a common voltage regulator type there is one oddity in measuring the bode response That is that the voltage reference is connected to the output voltage and not to ground For this reason the measurements for both Ch1 and Ch2 are referenced to Vout and not ground In most applications the probes will connect to ground WARNING Because the measurement is referenced to Vout and not Ground the output is effectively floating By connecting the ground clip leads of the scope probes to Vout of the regulator output ground is NOT the same as input ground and by adding any grounded equipment to output ground will result in a short circuit between the output and ground If this happens the 2 ohm resistor on the input ground side will act as the fuse burn out and the board will be unusable until the resistor is replaced Equipment List e Bode 100 or other network analyzer e J2100A or J2101A Injection Transformer e J2111A Current Injector e Two 1 1 scope probes or BNC cables with hooks or clips e J2140A Attenuator e LM317 Adjustable Regulator board Note In each measurement the J2111A Current Injector is used as a static 25mA load or a voltage controlled stepped load for load perturbations or both When using the oscillator of the Bode100
22. regulator Easily characterize fixed and adjustable regulators Making Measurements What s Included Your Voltage Regulator Test Standard Kit Includes Motherboard One 1 populated Regulator Boards One 1 LM317 adjustable regulator and one 1 TLV2217 fixed regulator two 2 blank boards Components Two 2 populated 2N 3904 BJT and Schottky Diode SR105 T three 3 blank boards Capacitor Boards Six 6 populated ceramic 0 1u 22u tantalum 100uf 15uf 2 2uf and electrolytic 100uf four 4 blank boards AC Wall Adapter One 1 100 240 AC 7 5V DC with worldwide plug set CD with documentation OMICRON Lab Bode 100 software and data files other support documentation Parts List Digi Key PN LM317TFS ND 296 21611 5 ND TLV2217 2N3904TFCT ND SR105DICT ND 399 4658 1 ND 100uF 6 3V 45mOhm 490 3811 ND 0 1uF X7R 493 1283 ND 100uF 16V 399 3741 1 ND 2 2uF 25V 3 5 Ohm 478 1707 1 ND 15uF 20V 1 7 Ohm 445 1422 1 ND 22uF 6 3V Figure 1 details the contents of the kit The supplied blank boards are not shown Making Measurements J2110A Adjustable Regulator LM317 3 3V Fixed Regulator TLV2217 3 3V Output gt N Capacitor Selections Injection Transformer Power Wall T Adapter Componentsto measure Schottky Diode Es SR105 T amp BJT 2N3903 CEN usse PITIA Current AM A c o es Figure 1 the contents of the Voltage Regulator
23. s placed on the input voltage bus Making Measurements 31 Crosstalk Crosstalk is a very closely related to reverse transfer and is another unappreciated and under analyzed characteristic of power systems If two regulators are on the same voltage bus and Regulator 1 experiences load perturbations Regulator 2 will experience voltage perturbations on its output Crosstalk is the measure of the Regulator 2 s output voltage to Regulator 1 s output current Equipment List e Bode 100 or other network analyzer e J2111A Current Injector e One 1 1 scope probe or BNC cable with a hook or clip e LM317 Adjustable Regulator board e TLV2217 Fixed Regulator board Connectivity Diagram APA OMICRON LA Add a jumper across top of J1 amp J2 WI PICOTEST COM lt gt PICOTEST www 9 lt otstcomtw monitor AC DC Vs t12V Max Current Injector Model NO J2111A Figure 17 Current Injector and board connections to the Bode100 Making Measurements 32 Data to Record Open the Bode file below to begin making the Crosstalk measurement Crosstalk Bode Calibrate the probes using the same process as the Bode measurement Press Run and the results should be similar to those in Figure 18 40 20 TR1 dB 10 103 104 105 108 107 t Hz mme R1 Mag Gain Figure 18 Crosstalk measurement shown as a voltage gain on the output of the TLV2217 test circuit as a re
24. sult of current perturbations on the LM317 test circuit Why is this important e Under dynamic loading conditions the voltages can go far below and above the DC regulation limits This can cause damage to the loads e The dynamic voltage response can have similar effects to ripple including degrading SNR BER phase noise jitter etc Making Measurements 33 Input Impedance The input impedance of a switching power supply or regulator is negative which is a stability concern when combined with an EMI filter making the measurement an important part of the design analysis and verification process Equipment List e Bode 100 or other network analyzer e J2111A Current Injector e J2120A Line Injector e J2101A Injection Transformer e One 1 1 scope probe or BNC cable with a hook or clip e LM317 Adjustable Regulator board Connectivity Diagram Bode 100 lt gt PICOTEST ww p al am tw E 1 4 50Vdc outra o E pog s 7 A banana cable to BNC adapter is A 10Hz 45MHz Injection Transformer Model NO J2101A CEE manam Line Injector Model NO J2120A CE x MADE IN TIWAN ii italia to connectthe transformer to the oscillator of the Line Injector with a BNC cable WWW PICOTEST COM Current Injector Model NO 121114 Figure 19 Line Injector and board connections to the Bode100 E our m used on the output of the transformer he injection transform
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26. to modulate J2111A s current over frequency the bias switch on the injector must be set to for positive output regulators the analyzer s inputs must be in Class A bias This also ensures the J2111A will not try to draw a negative current from the regulator Making Measurements 13 Connectivity Diagram HighO HighO r5 INPUT OMICRON CI LAB PICOTEST ra Docobed co D 1 1 8 E eu SOOC 10Hz 45MHz Injection Transformer Model NO J2101A C Ta i MADE DO Do Add a jumper across top of J1 J2 WWW PICOTEST COM lt gt PICOTEST www picotstcomtw monitor AC DC Vs 112V Max Current Injector Model NO J2111A CER Figure 2 Bode measurement connection diagram The current injector is connected to the output of the regulator to provide a 25mA load on the regulator Make sure the bias switch is switched toward the bias side on the J2111A Current Injector to provide this 25mA Power the demo board with the 7 5V wall adapter and the J2111A Current Injector with the J2170A High PSRR Regulated Adaptor Calibrating the setup With the equipment connected as shown in the connection diagram and power applied connect both the CH1 and CH2 probes to pin 4 on the Bode connector on the ADJ regulator board J4 Connect the ground clips of both probes to either pin of J3 These two pins are connected together on the PCB Open the fo
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