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TPS23750: POE not working

USHA M
Intellectual 290 points
Part Number: TPS23750

Hi ,

Attached is the POE section schematics that is implemented in our design. We are facing a issue when we power up the board with POE adapter (48V). MOSFET SI4840DY-T1-E3 is getting shorted between source and drain shorting the POE power(VCC_5V0_POE) . Please let us know the is there any issue with the design.

0763.POE.pdf

Thanks,

Usha

  • 0
    TI__Intellectual 1695 points
    Hi Usha,

    Nothing catches my eyes on the EVM.
    It is possible that the SYNC FET SI4840DY-T1-E1 is damaged and will short the output.
    Please check the VDS and VGS waveform to check the voltage stress.
    1. There will be a negative spike on VGS and it shouldn't be over the range of FET.
    2. There will be a positive spike on VDS and it shouldn't be out of the normal range of FET. You can add an RC snubber paralleled with FET R=10 C=2200pF. And it can be adjusted through the real case.

    Thank you.
    Best Regards
    Jack Chen