TPS51200: Input and Output Capacitance

Matthew Swanson

Part Number: TPS51200

Hello,

The datasheet for the TPS51200 part recommends using 1/2 of the output capacitance on the input. Our current design has about 30uF capacitance right at the output of the converter and about an extra 400uF local to the DDR4 memory. I was planning to put about 20uF on the input but am wondering if I need closer to 0.5*430uF = 215uF on the input as the datasheet recommends. Can you please confirm if the 20uF is sufficient or if I should target closer to 215uF.

Thanks!

Matt

over 6 years ago

0 Qian Chen over 6 years ago

TI__Mastermind 24075 points

Hi Matt,

I don't think you need 215uF for input cap.
It will be good if you can put total 100uF at input side. Because voltage is low, you can use ceramic cap with small package size, such as 22uF 0603 cap.

Thanks
Qian

0 Matthew Swanson over 6 years ago in reply to Qian Chen

Prodigy 100 points

Qian,

Thanks for the response. I wanted to also note that I received some other comments that it may be helpful to simulate the part. One concern is that during initial start after the enable threshold is reached, the input voltage may drop due to the inrush current if there is insufficient decoupling. Modeling capacitor tolerance, ESR and board impedance will show these effects. The model can be found here:

http://www.ti.com/product/TPS51200/toolssoftware

Thanks!

Matt

Power management

Power management forum

TPS51200: Input and Output Capacitance