TPS54331: TPS54331DR 12V buck to 5V and 5V vout has about 40KHZ Ripple

Cheney_Sun

Intellectual 595 points

Part Number: TPS54331

Dear TI EE:

The circuit using TPS54331DR as 12V Buck to 5V function as bellow picture

The 5V Vout has about 40KHZ ripple as bellow waveform picture

The TPS54331DR Comp Pin6 to GND Voltage as bellow picture

Please help to solve the proble,I am anxiously awaiting a solution.

Thank you!

Best Regards

Cheney_Sun

over 6 years ago

0 Shawn Nie over 6 years ago

TI__Genius 10070 points

Hi,

The L and Cout values are not applicable, L=6.8uH would be better, and 10*560uF is too large. The system would be unstable.

For the 40kHz ripple, it is strange, are this waveform tested on the board? What is the load? Where does the input voltage come from?

Shawn

0 Cheney_Sun over 6 years ago in reply to Shawn Nie

Intellectual 595 points

Hi Shawn:
Sorry to reply now.
Update the data as bellow,12V Buck to 5V
L=22uH，and Total Cout is about 580uF.The Cout cap is as follow: 220uF(AL Cap)//220uF(AL Cap)//100uF(AL Cap)//10uF(MLCC)*4
Please help to make sure if the Rcomp:249kohm,Ccomp:2200pF,Ccomp2:10pF is suitable for the circuit.
Thank you!
Cheney_Sun

0 Shawn Nie over 6 years ago in reply to Cheney_Sun

TI__Genius 10070 points

Hi,

Rcomp is too large, you can try to change it to 29.4kohm, and as I have mentioned, 22uH inductor is too large, 6.8uH would be better.

Shawn

Power management

Power management forum

TPS54331: TPS54331DR 12V buck to 5V and 5V vout has about 40KHZ Ripple