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TPS51397A: WEBENCH Design

user3668508
Prodigy 180 points
Part Number: TPS51397A


At what hertz is the ESR of the capacitor in the designed schematic?

  • 0
    TI__Expert 5470 points

    Hi,

    Do you mean the frequency of ESR zero? Its frequency equals to 1/(Co*ESR_co*2*PI) with unit Hz.

    By the way, TPS51397A applies D-CAP3 control with internal zero created by "ripple injection" circuit. Its stability doesn't rely on the output cap ESR zero. So you can use all MLCC with small ESR.

    Thanks,

    Andrew

  • 0 in reply to Andrew Xiong
    Prodigy 180 points

    Hi Andrew,

    Thank you for your reply.

    The meaning of the question is not the frequency of ESR zero.
    For example, I designed a circuit using WEBENCH with TPS51397A.

    The conditions are Vin (min) = 10.8V, Vin (max) = 13.2V, Vout = 5V, Iout = 5A.
    Each of the Cin, Cinx, and Cout of the designed schematic has a milliΩ ESR requirement.

    What is the condition for this milliΩ ESR at what hertz? Should I choose a capacitor with this milliΩ ESR that must be met in all frequency bands?

    Thanks,

    Sato

  • +1 in reply to user3668508
    TI__Expert 7500 points

    Hi Sato,

    If you use all MLCC of the Cin and Cout, we can ignore the ESR influence. And for TPS51397A, it can support all MLCC.

    Thanks,

    Lishuang