# Need Help Finding Inductor Value!

Hello,

I am trying to find the inductor value for a circuit involving a TPS6107.
http://www.ti.com/product/TPS61070/datasheet/application_and_implementation#SLVS5103348 I used this link,section 11.2.2.2 for my calculations.

My values are
Output Voltage = Vout = 5v
Initial Voltage = Vbat = 3.7v
Desired Current = Io = 380mA
Switching Frequency = f = 1200 kHz

I begin by trying to find the "maximum average inductor current", equation 3, which they say is equal to Io * (Vout/(Vbat*.8)). Plugging my values in, I get 641.89mA.

Now for the next part, I compute L with equation 4. I assume that the maximum average inductor current is the "ripple current",delta I sub(L), because in the link, equation 3 is supposed to represent the maximum average inductor current but I believe the symbol does not load correctly as only the subscript L is shown. So I use 640 mA, w respect to sig figs, as my ripple current. I plug my my values in for equation for 4 and get .00000125 = L.

My questions are:

Was I right to assume the maximum average inductor current is the ripple current?

For equation 3, Vbat is multiplied by .8 but the efficiency of my booster is .9. Should .9 be there instead or is there no relation?

Author
John Miller
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