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Summary of Contents for Picotest J2122A
- Page 1 ® J2122A User Guide Copyright © 2024 PICOTEST www.picotest.com.tw...
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Page 2: Table Of Contents
Contents Foreword ........................... 3 Package Contents ......................4 Before Use ......................... 5 Connection Before Testing ....................7 About Vdrop and DC Output Adjustment ............... 11 Using the Remote Sensing Compensation Board PWR-OPT05 ........12 PSRR Connection Testing ....................16 Summary: ........................24... -
Page 3: Foreword
With its wide frequency response, adjustable voltage, high-intensity signal injection, and convenience in eliminating complex power wiring, the J2122A will be a reliable assistant in your signal processing tasks. In PSRR measurement applications, a DC power supply voltage can be input to the line injector, which is then modulated by the source signal from a Frequency Response Analyzer (FRA). -
Page 4: Package Contents
To conduct a PSRR test, a sine wave must be injected at the DC input, sweeping from low frequency to high frequency. This measurement requires a DC + AC summing device, such as the Picotest J2122A line injector. The measurement system simultaneously measures the modulated input and output AC voltage levels, and then calculates the suppression ratio for each frequency within the sweep range using the formula 20Log(Vin/Vout). -
Page 5: Before Use
Charge is required before use. The charging indicator is red during charging and turns green when fully charged. Figure 3 : J2122A with red light, during charging Figure 4: J2122A with green light, fully charged Figure 3-1: Power Indicator Lights... - Page 6 Figure 3-3: USB Type-C Charging Port The USB Type-C charging port shown on Figure 3-3 is for charging only. When J2122A is being charged, the power switch will automatically turn off and cannot be operated. A...
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Page 7: Connection Before Testing
DC power supply, and OUT connects to the oscilloscope or load. Turn on the J2122A power supply; the indicator light should be on (green). Set the power supply to output 3V, set the signal source to 1kHz or 1MHz, 1Vpp, and set the oscilloscope channel to either 1MΩ... - Page 8 3V, and the signal generator outputs 1kHz, 1Vpp. Figure 6: The Oscilloscope State after the settings are settled down. If the waveform amplitude appears abnormal, adjust the Vdrop knob with the tool in the package. Figure 7: The Vdrop adj Location Adjust the knob to ensure that the waveform is undistorted and has a normal Vdrop.
- Page 9 Figure 8: The distortion waveform that user need to avoid Readjust to ensure that the waveform is undistorted and that the Vdrop meets the required specifications. As shown in Figure 9, the signal amplitude matches that of the signal source, with a Vdrop of approximately 1V. Subsequent tests can compensate for the corresponding Vdrop by increasing the power supply output.
- Page 10 Figure 10 shows the oscilloscope channel impedance set to 1MΩ, with the signal source set to 2Vpp and the signal source output impedance set to high Z, for reference only. After completing the adjustments to the injector as described above, you can adjust the settings of the signal source and power supply as needed, connect the device under test, and prepare to start testing.
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Page 11: About Vdrop And Dc Output Adjustment
DC power supply. Compared to the J2120A, the Vdrop of the J2120A can range from 0.7V to 3.25V, with specific values dependent on the load current size. The J2122A allows for fixed Vdrop adjustments via a knob. -
Page 12: Using The Remote Sensing Compensation Board Pwr-Opt05
Principle of Remote Compensation with PWR-OPT05 If the output of the J2122A is fed back directly without filtering, the power supply's remote sensing function will adjust away the modulated signal. The output of the J2122A is filtered and sensed through an RC network to adjust for voltage drops caused by load current. - Page 13 Figure 13 shows the connection diagram for measuring PSRR using remote sensing to compensate for voltage drops induced by the J2122A. Again, a fixed offset of 75 mV is generated due to the series connection of the 24.9 Ω filter resistor with the internal power supply divider resistor.
- Page 14 Figure 14: Schematic Diagram of the Remote Sensing Filter and PWR-OPT05 According to the parameters set in Figure 9, the oscilloscope channel impedance is 50Ω, the power supply outputs 3V DC, the remote sensing feature of the power supply is enabled, and the signal generator is set to 1kHz, 1Vpp with an output impedance of 50Ω.
- Page 15 Figure 16: the power supply can automatically readjust the DC voltage drop...
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Page 16: Psrr Connection Testing
6. PSRR Connection Testing Using E5061B for PSRR testing. The connection method is shown in the following figure. Figure 17: PSRR Connection The test results are similar to the following figure. Figure 18: The PSRR Test Result... - Page 17 Using an oscilloscope for PSRR testing Taking Keysight's HD304MSO as an example, the connection method is shown in the following figure. Figure 19: The PSRR Test via Keysight’s HD304MSO *Before using the oscilloscope, probe calibration is required. After connecting as shown in the figure: 1.
- Page 18 Figure 20: Set the frequency range and signal source amplitude Frequency Mode: You can scan the entire frequency range or perform analysis at a single frequency. Single frequency point mode is very useful for evaluating amplitude at a single frequency. After running tests at a single frequency, you can manually...
- Page 19 adjust (increase) the waveform generator's amplitude until you observe waveform distortion on the oscilloscope display. You can then use this amplitude in scan mode for all frequencies or evaluate amplitudes at other frequencies to determine an optimized amplitude profile. Start Freq: Set the starting frequency value for scanning. Stop Freq: Set the stopping frequency value for scanning.
- Page 20 5. Click Run Analysis to run the test. 6. Wait for the program to finish and check the test results. Figure 21: The Test Result Note: If the test results show negative values, you need to switch the input and output channel settings in the channel setup.
- Page 21 We can optimize the display curve by turning off the displays of channels 1 and 2 and adjusting the channel display coordinates. You can drag the marker arrow to the point you want to observe to see the corresponding test results (upper right corner of the screen). Using an external mouse will make operation more convenient.
- Page 22 Figure 25: Show the PSRR measurement results based on custom test amplitudes After completing the test, using the cursor, we measured a maximum suppression of 55 dB at 100Hz and a minimum suppression of 7 dB at 20 MHz (the final test frequency), with insufficient suppression above 319 kHz.
- Page 23 Figure 26: The PSRR measurements via Keysight’s Oscilloscope Alternatively, as shown in Figure 27, in the frequency response test dialog box, select single-frequency testing, input the required frequency point and amplitude value, and click run. Figure 27: The frequency response test dialog box...
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Page 24: Summary
Figure 28: Run single-frequency tests while manually adjusting amplitude and frequency in the oscilloscope's WaveGen settings menu 7. Summary: We have demonstrated a simple method for measuring LDOs using the Picotest signal injector and Keysight's HD304MSO InfiniiVision. Using Keysight's HD304MSO InfiniiVision oscilloscope makes it easier to test the PSRR of devices, allowing you to see distortion in input and output signals during testing, facilitating adjustments to testing parameters for more accurate test results.
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