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TPS54320: TPS54320 phase margins

Wang Kris
Intellectual 270 points
Part Number: TPS54320

Dear Sir:

The TPS54320 datasheet page. 27, 8.2.2.9 Compensation Component Selection

"There are several industry techniques used to compensate DC/DC regulators. The method presented here is
easy to calculate and yields high phase margins. For most conditions, the regulator has a phase margin between
60° and 90°."

May I know why the TPS54320 phase margins suggest a design between 60 and 90,

If it is for industrial applications to be such a design,

That didn't see the recommendation in other converters datasheet.

Is there any reason for this advice?

  • 0
    TI__Guru**** 191445 points
    Generally you want a minimum phase margin of 45 degrees. That is a common value you will see in a lot of control loop theory texts. 60 degrees is a good target value that I usually design for. If I get higher phase margin than 65 degrees or so, I typically will extend the loop BW until the phase margin drops to around 60 degrees. With current mode control, it is common for the slope of the phase characteristic to be dropping somewhat rapidly at the crossover frequency, so some extra margin above 45 degrees is a good design practice. If you look at figure 47 in the TPS54320 datasheet, you can see the phase is dropping rapidly at higher frequencies.