LM25149-Q1: About parameter calculations and application design

Guohai Lin

Part Number: LM25149-Q1

Hi teams，

I hope you’re doing well!

Can you help explain how the following parameters are calculated?

For example, how do we get Fc=60KHz and Cout=100uF in the calculation formula of Rcomp?

Is Cbw=31pF a fixed value? If not, how did you get it? How is the value of fESR calculated?

Thanks!

0 Orlando Murray over 1 year ago

Hi Guohai,

The Fc crossover frequency is selected, usually between 1/10-1/5 of switching frequency.

The output capacitance is usually selected by other parameters, such as output ripple or transient response.

CBW is fixed. Fesr is calculated by the ESR of the output capacitance. fESR = 1/(2*pi*COUT*ESR)

BTW, the compensation calculation can be helped with the quickstart calculator: https://www.ti.com/tool/LM5149-LM25149DESIGN-CALC

Hope this helps,

-Orlando

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