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TPS65130 15V overshoot and ringing

Randy Steck
Prodigy 10 points

We are seeing some significant overshoot and ringing on the VPOS output of a 65130 regulator.  Power save mode is selected and when the burst regulation occurs we see a 0.8 volt overshoot and ringing.  This is very problematic as the +/-15V supplies are used for an audio amp.

Even though we have the same connections for the -15V output we are not seeing the same thing with it.

Can you help us figure out how to eliminate this massive noise problem?  Circuit and scope output of +15V attached.

Load for both +15 and -15 supplies are only about 40mA.

Doc1.pdf

  • 0
    TI__Guru 65280 points

    Hello Randy,

    0.8V of ripple due to power save mode sounds too high. It should be in the range of 100mV.

    Is it possible that some of the output capacitors shown in the schematic are possibly not populated on the board? Please check as well if C33 is populated correctly.

    The schematic you sent shows an inductor of 6.8uH for both converters. For a fast reaction of the converter it is recommended to use a smaller inductor, so I would recommend using a 4.7uH inductor instead. This makes the loop faster and in addition the compensation fits better.

    If these checks and changes are not helpful, please send some more measurements. I am sorry, but I could not understand what you measured in your pdf file. The following signals would be interesting to observe during the high ripple:
    - VPOS
    - INP
    - CP
    - output current of the boost converter

    Best regards,
    Brigitte