TPS54A20: Series Capacitor Selection of Buck converter

Expert 1125 points

Part Number: TPS54A20

Hi TI Experts,

I would like to know how to choose the Series Capacitor Selection of Buck converter.

In this document, it uses SPEIC to calculate the Series Capacitor. but don't mention the buck converter.

https://www.ti.com/lit/ds/symlink/tps54a20.pdf?ts=1678501186478&ref_url=https%253A%252F%252Fwww.google.com%252F

Could you please give me some suggestions on it, thanks?

over 2 years ago

0 Yitzhak Bolurian over 2 years ago

TI__Mastermind 18370 points

Hello Jack,

The datasheet clearly mentions how to calculate the series capacitor.
The calculation is for TPS54A20 acting as a buck converter.

It just mentions that the energy transfer by Ct resembles the operation of a SEPIC converter.
You can ignore the extra comment about SEPIC, and just use Equation 13/14.

Regards,

Yitzhak Bolurian

0 J over 2 years ago in reply to Yitzhak Bolurian

Expert 1125 points

Hi Yitzhak,

May I know how to get equations 13 and 16?

COuld you please explain it to me, thanks.

Jack

+1 Tahar Allag over 2 years ago in reply to J

TI__Mastermind 32500 points

Hello Jack,

Equation 13 is basic change in voltage across a capacitor given the change in time/fsw and the capacitance of the capacitor. That is re-arranged to provide the design equation for series capacitor Ct as in equation 14.

Equation 16 is driven from equation 15

Thanks!

Tahar

0 J over 2 years ago in reply to Tahar Allag

Expert 1125 points

Thanks.

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TPS54A20: Series Capacitor Selection of Buck converter