# Estimating heat desipation of MOSFET

#### anishkgt

Joined Mar 21, 2017
549
To calculate the inductor

In the equation, what is f and L ? Is the Frequency same as Switching Frequency (Fsw) ?

#### anishkgt

Joined Mar 21, 2017
549
Based on my application Vout = 8.1v, Vin = 12, Ton = 833 (pg 10). The Fsw = (Vout/(Vin x Ton)) x 10^6 = 810kHz

I have read that switching at a higher frequency is better, so how high is HIGH ? Is inductance a constant value set in the datasheet ?

#### jpanhalt

Joined Jan 18, 2008
11,087
Just so the inductor is big enough and can handle the current. Here'd a classic by Jim Williams -- a great engineer with a sense of humor:
http://cds.linear.com/docs/en/application-note/an35f.pdf

Be sure to check out Appendix B, which is from his earlier application note on the same subject. Look for "Safeway" (Figure B8).

#### anishkgt

Joined Mar 21, 2017
549
Just so the inductor is big enough and can handle the current. Here'd a classic by Jim Williams -- a great engineer with a sense of humor:
http://cds.linear.com/docs/en/application-note/an35f.pdf

Be sure to check out Appendix B, which is from his earlier application note on the same subject. Look for "Safeway" (Figure B8).
The link seems to be broken, or my ISP does not allow non SSL pages.

#### jpanhalt

Joined Jan 18, 2008
11,087
Here's the pdf. I always check links, and that worked when I posted it. Now, I get an error too.

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#### anishkgt

Joined Mar 21, 2017
549
I guess things are clearer with this simulation from RedExpert. Registration is not required. With the lack of knowledge i have, am just not sure if i should go ahead with what the simulation says. Will wait for a confirmation.

Simulation values
Vin(min) = 12, Vin(nom) = 12, Vin(max) = 12
Vout = 8.1v , Iout = 10A
fsw = 810kHz
Delta iL = 40%

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