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LM5088 R_ramp and V_ramp calculation

Christian Willschek90
Prodigy 715 points
Other Parts Discussed in Thread: LM5088

Hi,

how do I calculate the R-ramp? I found a formula in the data sheet (http://www.ti.com/lit/ds/symlink/lm5088.pdf), page 22, formula 15. However I don´t know V_ramp to do the math.


Can you help?

Thanks

Christian

  • 0
    TI__Mastermind 21720 points

    Christian,

    Please take Vramp to be the equation below.This is just based off of the current that is sourced from the LM5088's RAMP pin.

    Vramp = [(gm*(Vin-Vout)+25uA]*[(Vout/(Vin*fsw*Cramp)]

    Where

    gm = 5uA/V

    Vin = Input voltage

    Vout = Output voltage

    fsw= switching frequency

    Cramp = selected ramp resistor

    -Garrett