TPS56C215: TPS56C215 Equation 1

Hi,

You can refer to the "Recommended Component Values" for the choose of components and it's much easier. Or using Webench designer is a much easy way to choose inductance and capacitance.

For the meaning of equation (1), I can give you some explanation here:

If loop gain cross 0dB with -20dB/decade, the system tends to have sufficient phase margin for stability. The frequency that gain cross 0dB is called the crossover frequency. In D-CAP converter, the double pole will change the slope of gain from 0dB/decade to -40dB/decade at frequency fp. If zero location is between fp and crossover frequency, that's a stable (-40+20)=-20dB/decade crossing. If zero location is far from fp and even higher than crossover frequency, that's a unstable -40dB/decade crossing. So we need to ensure the zero location is between fp and crossover frequency for stability. Since the crossover frequency is determined by a lot of factors, the easy way is to keep fp close to zero location.

That's a simple principle for the LC choose in D-CAP converter from loop stability view. For the detailed analysis, I'm writing an application report about this and will be released recently.

Thanks,

Andrew