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Original question:

TPS54428: Could you tell me about TPS54428's CBST capacitance ?

TPS54428: CBST max allowed value

NY
Expert 3040 points
Part Number: TPS54428

Hello, 

Due to MLCC shortage, customer want to use even higher value of C7, if allowed, C7=10uF. 

Basically, huge capacitance takes more time of charging voltage for high-side switch, does this impact on minimum on time, which may be longer than max of specified in d/s?

Please let me know if my understanding is correct or not.

Regards, ny

  • 0
    TI__Expert 4720 points
    Hi,
    It only affect the behavior at power up. When startup, the 10uF cap took longer time to charge to a proper high value. The cap voltage is used to turn on the HS MOSFET, if the voltage is not high enough, HS MOSFET can't be turned on.
    If the IC power up successfully, Then the IC works normally after that. The minimum on time is not affected.
    10uF is quite a big value, we haven't qualified that, and need to experiment to verify. Please check at Vinmin, Voutmax, Ioutmin on your board, to check the power up process.
  • 0 in reply to Neal Zhang
    TI__Expert 3040 points
    Hi Zhang, thank you very much