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TPS54A20: How many variables have you substituted for each of the inductor equations (4)?

gomi.ryota
Prodigy 140 points
Part Number: TPS54A20

Hi, TI expert

How many variables have you substituted for each of the inductor equations (4)?

K(IND) ＝ 0.4 , Vout = ?, Vin = ?, Iout = ?, Fsw = ?

Best regards.

  • +1
    TI__Intellectual 890 points

    Hello,
    The values for the variables comes from the design requirements as seen on page 23 of the datasheet. Hence, we are given the values for the missing 4 variables. K(IND) = 0.4, which was said on page 24 of the datasheet. On page 23, the rest of the values are written under 8.2.1 Design Requirements.

    Vout = 1.2 V, Vin,max = 14 V. Iout = 10 A, Fsw = 2 MHz.

    Then, you can just put these values into equation 4. Lout = (2*Vout(Vin,max - 2Vout))/(Kind*Iout*Vinmax*Fsw) = (2*1.2V(14V-2*1.2V))/(0.4*10A*14V*2MHz) = 249 nH. However, for the design in the datasheet, they used a nearby value inductor of 220 nH.