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Original question:

UCC28742: UCC28742 frequency question

UCC28742: Input Bulk Capacitance Calculation

Naizeng Wang
Expert 5380 points
Part Number: UCC28742

Hi team.

I think the formula in 8.2.2.4 is wrong. There shouldn't be a "2" in front of Vin(min). Right?

Br,

Naizeng

  • +1
    TI__Mastermind 40100 points

    Hello Naizeng,

    The formula for Cbulk is correct with "2" in front of Vin(min).
    Here, Vin is an RMS value. 

    The denominator is subtracting the energy of the minimum bulk valley voltage from the energy of the minimum line peak voltage.
    The line peak is sqrt(2)*Vin(min).  The square of [sqrt(2)*Vin(min)] is 2*Vin(min)^2. 

    The formula in 8.2.2.4 is correct.

    Regards,
    Ulrich