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TPS7A20: Inquiring about abnormal output characteristics

Part Number: TPS7A20

I have organized my question and detailed description into a PDF file for easier reading. Additionally, English is not my native language, so please forgive me if there are any mistakes in my descriptions. 

      3755.TPS7A2036DBVR trouble.pdf     

  • Hey An, 

    If you connect directly to the PCB, does anything change on the waveform? Specifically connecting the input directly to the PCB input?



  • Thank you for your suggestion. I have made some modifications and conducted the experiment again. Here are the results:

    1. I have modified the circuit's connection method. Currently, apart from the thick film resistor of the load and the Enable Pin, which are connected via a breadboard (I have tested both connections, soldering to the PCB and connecting via a breadboard, and they do not affect the output), all other circuits and input/output capacitors are directly soldered to the PCB.
    2. Comparing to the circuit before the modification, the current connection indeed shows some improvement in the output. With a load greater than 100Ω, the output stabilizes at 3.6V and exhibits no significant Ripple (at this point, the oscilloscope displays a Vp-p of only around 2mV, which is very normal). Moreover, even after removing the load, the output remains stable at 3.6V. However, as the load continues to increase, below 100Ω, the output's Ripple Vp-p starts to increase, as shown in the picture. Nevertheless, when measuring the output using a desktop multimeter, it remains stable at 3.6Vdc.
    3. Additionally, I have observed that the input voltage and the output Ripple Vp-p are directly proportional.
  • Hey An,

    I think this may be happening from the bench set up, if you ad a large capacitor to your power supply, does it fix the issue further? 

    the desktop multimeter is most likely giving you an average reading of the output. 

    A 5V input to a 3.6V output should provide enough headroom for your application.