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TPS54329: Questions of TPS54329

Jimmy Lai
Expert 6845 points
Part Number: TPS54329

Dear Team,

Below is the circuit we used for the 3.3V power rail. Concerning the soft-start time, we modified CB39 from 3300pF to 470pF as part of power sequence optimization. However, after this change, several units failed to boot up. In the failing unit, the problematic rail was with a voltage around 1.35V. Could you please check if there is a limitation on the capacitance adjustment for soft-start? Thank you.

3.3V output, measured at C38, after power on.

 

CB39 = 3300pF

CB39 = 470pF

Many Thanks,

Jimmy

  • 0
    TI__Expert 8100 points

    Hi Jimmy,

    Thanks for reaching out. I would like to know following information at present:

    1. What about failure rate?

    2. Could it be replicated on EVM?

    3. Does device start with loading added? If loading is added, what is the value of the loading?

    4. Does the problem occur at first start-up process or start-up process after shortly shutdown?

    I do not observe Vout stable at 1.5V. Attached figures are both 3.3Vout. What about waveform of failed parts?

    And please ask customer to capture Vin+SS+Vout+SW for three conditions: startup under 3300pF SS cap, normal startup under 470pF SS cap, failed startup under 470pF SS cap. Thanks!

    BRs

    Zixu