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TPS54202: Question about TPS54202 soft-start time abnormal behavior

Jacky Wang(QD)
Genius 11530 points
Part Number: TPS54202

Hi Experts,

Our customer is using our TPS54202 in their project with 2 different boards, but having the same schematic and external components. During their test, they found that one board soft-start time for TPS54202 is only about 2ms, but with the same chip changed to another board, it will have 5ms soft-start time matched our spec.

Do you know what's possible reason why soft-start time is decreased? As we understand it is fixed inside our device. Is there any other external components will influence it?

Abnormal soft-start time measured:

Attached is customer's schematic FYI.

  • 0
    TI__Expert 4035 points

    Hi Jacky,

    Could you please upload the layout snapshot of those two boards? Also you need check if any loading difference at the output of TPS54202 on those two boards during soft start.

  • 0 in reply to Ryan Hu (BSR-MV)
    TI__Genius 11530 points

    Hi Ryan,

    Please refer to below customer's PCB layout for the SS time measured around 2ms, also customer made the test with no load added on the output, it could not be affected by loading. Any other ideas about the SS time changing? I think it should be fixed inside the IC.

    Thanks.

  • 0 in reply to Jacky Wang(QD)
    TI__Expert 4035 points

    Hi Jacky,

    The layout is bad. Please refer to the datasheet recommend layout example for re-layout in future.

    For the soft time issue in this thread, I found the IC GND is not connected to other GND net, I guess it was connected by the RJ8?  It would be the critical reason. Here should have a short GND trance between the IC GND and other GND net like the input and feedback. Please double check your customer's another board layout.