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LMR33630: Output Capacitor

Peter Xu
Expert 7885 points

Part Number: LMR33630

Hi team,

My customer wants to use LMR33630 for 20V/100mA max output. They want to use less capacitor for lower cost. For 2A situation, it's 4*22uF capacitance. And which value is suitable for 20V/100mA occasion?

Best Regards,

Peter

  • 0
    TI__Mastermind 31156 points

    Hi Peter

    You can refer to the calculation tool. But please be aware that the recommended value are the effective values considering DC bias for Caps.

    LMR336x0_calculator_A0.xlsx

    Thanks and best regards.

  • +1 in reply to Gui He
    TI__Mastermind 31156 points

    Hi Peter

    I will close this thread for now, you can reopen or ask new question if have further questions.

    Thanks and best regards.

  • 0 in reply to Gui He
    TI__Expert 7885 points

    Hi Gui,

    I check this file with my customer. And we left some question after discussion.

    1. The actual inductance value is smaller than the calculated one. It seems unreasonable. How can we explain it?

    2. The output capacitance is larger than the calculated one. Does it mean that the actual one is rating value and the calculated one is derating value?

    3. What factors are related to feedforward value? We find it hardly changes when we change input and output values.

    BRs,

    Peter

  • +1 in reply to Peter Xu
    TI__Mastermind 31156 points

    Hi Peter

    The actual inductance value is not a calculated value, it's for you to input the actual value you chose on board.

    Same with the Cout value. The Actual output capacitance is to be inputed and should be actual value considered derating.

    Please see equation(9) in datasheet. It's a good starting point to have Cff NC at first.

    Thanks and best regards.