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TPS54360B: Power Output without Input in Test Environment

Kyle Mehringer
Intellectual 1100 points
Part Number: TPS54360B

Hello,

TPS54360B is being used for a 48Vin to 12Vout application.

In a testing environment, is it okay to supply power just to the output of the TPS54360B, with no input? This is to try to bypass the TPS54360B in a test environment and just use 12V (supplied elsewhere externally) to power up the board for programming and easy test.

We don’t seem to see any body diode that can leak power backwards to input, and the VRD should in a disabled stage. Are there any things that we need to pay attention to in this testing case?

Thank you,

Kyle

  • 0
    TI__Guru 64365 points

    Hello

    There is a path from the output of the regulator toward the input through the body diode of the power MOSFET internal to the converter.

    This path is not shown in the block diagram explicitly, however there will always be a body diode from source to drain in a NMOS FET.

    It is usually not a good idea to "back-feed" a regulator unless you can pull the EN input low and shut down the converter during your testing.

    Even so, there may be large surge currents through the body diode when you apply your external 12V that may weaken the FET structure.

    This will depend on what is on the input side of the regulator and your other conditions.

    It may be a good idea for you to try your testing while monitoring the input voltage, switch voltage and current from your external supply.

    We can then examine the waveforms and assess the situation a little better.

    I have also attached and application note that may be helpful.

    Thanks

    slyt689_backfeed.pdf

  • 0 in reply to Frank De Stasi
    TI__Intellectual 1100 points

    Hello Frank,

    Is there an easy way to see this on an EVM? Do you have recommended steps to do so? Which waveforms would you like to see?

    Thank you,

    Kyle

  • 0 in reply to Kyle Mehringer
    TI__Guru 64365 points

    Hello

    Yes you can test using an EVM under your conditions and procedures.

    It would be good to see the input voltage, SW node voltage, and external supply current, along with

    any other relevant waveforms.

    Thanks

  • 0 in reply to Frank De Stasi
    TI__Guru 64365 points

    Hello

    I will close this post due to inactivity.

    You can re-open if you need more help.

    Thanks