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Input capacitor of TPS54328

Other Parts Discussed in Thread: TPS54328

We have questions about input capacitor of TPS54328.

In datasheet p.13  8.2.2.3 Input Capacitor Selection,

 TI recommends a ceramic capacitor over 10 µF for the decoupling capacitor. 

Question 1.

Please tell us the reason why you recommend over 10μF.

Question 2.

Can we use the capacitor lower than 10μF?

Please tell us the minimum capacitance and the reason if we can use lower than 10μF.

Question 3.

What happens to the IC if we use the capacitor lower than 10μF.

Best regards,

Takahiro Nishizawa

  • Hi,

    Sufficient input capacitance is important to guarantee the buck converter working normally.

    As the high side switch turns on, the VIN of the converter will suddenly draw a high current. Input capacitance helps to provide this input current. Without sufficient input capacitance, the voltage seen on VIN pin may drop a lot, even below the UVLO threshold. 

    Regards,

    Sam

  • Thank you for your answer!


    Our customer try to use lower than 10μF.
    Should we avoid using the capacitor lower than 10μF?

    please tell us the reason why you recommend the capacitor over than 10μF.
    Why do you think that over 10μF is working normally.

    Best regards,


    Takahiro Nishizawa
  • Hi,

    As suggested in the datasheet, please use a minimum 10uF capacitance for the input. We can't guarantee the converter will work well with smaller input capacitance. Also, please place the input capacitor with the VIN as close as possible.
    Thanks!

    Regards,
    Sam