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TPS54202: To Delay enable device

Nam, Dino
Expert 6445 points
Part Number: TPS54202
Other Parts Discussed in Thread: TPS62933

Dear team, 

My customer would like to design external delay circuit like below. 

1. Is it possible to delay enable device to 400~500ms using external single capacitor like above? 

2. Is there any side effect using external capacitor on EN port. 

3. Would you recommend another way to delay enable device? 

Please review it and let me know your opinion. 

Thank you.  

  • 0
    TI__Genius 9480 points

    Hi ,

    I will check this and feedback to you later.

    BRs,

    YZ

  • +1
    TI__Genius 9480 points

    Hi ,

    This method you mentioned work on bench. You can add one more cap parallel with R5 to delay enable .

    There is one concern this delay time is vary with the loading . Heavy load will shrink the delay time as the input current would be larger and charge this cap faster than light load. You can double check on EVM ,too.

    And may I ask why you need this delay time to enable devices ? 

    or you need soft start feature ?

    BRs,

    Young

  • 0 in reply to Young Zhao
    TI__Expert 6445 points

    Hi Young, 

    Thank you for your comment. I will try it as your recommendation. 

    The reason why I'm asking delay time to enable device is power sequence of the customer application. 

    Currently, they can't add digital enable signal to enable TPS54202 so they would like to add analog delay circuit. 

    The soft start feature is one of solution to solve customer issue but TPS54202 is fixed 5ms soft start. Is there any way to change soft start time of TPS54202?

    Thank you. 

  • 0 in reply to Nam, Dino
    TI__Genius 9480 points

    Hi Dino,

    As you said , digital control would be the better solution than add cap parallel with resistor  .And soft start is fixed for TPS54X02 parts. 

    And you can try TPS62933 which is a new released 30V3A buck with soft start feature in SOT583 pkg, if customer has concern with above solution .

    BRs,

    Young