TPS54821: TPS54821 issue

Big Bill

Expert 1980 points

Part Number: TPS54821

Dear All

I use the TPS54821 to design buck circuit 5V--1V， the schematic as below

when the no loading condition, the output voltage wave as below, it looks like wrong wave , can you help me what cause the result and how to improve the wave, thanks~

over 5 years ago

0 Iven Su over 5 years ago

TI__Expert 8245 points

Hi,

The compensation needs improvments. Try larger 1uH L8. Change C136 to 75pF, R99 to 6.34kOhm, C138 to 1500pF.

0 Edwin Zang over 5 years ago

TI__Expert 6425 points

hello Bill,

Do you mean 8A loading is no problem, right? Please also capture SW waveform and upload the waveform.

For 1Vout, it actually don't need CFF cap(C50). and 470pF is too large. please have a try to remove C50.

best regard,

Edwin.

0 Big Bill over 5 years ago in reply to Edwin Zang

Expert 1980 points

Dear Edwin:

there is same problem whatever loading or not .

0 Edwin Zang over 5 years ago in reply to Big Bill

TI__Expert 6425 points

Dear Bill,
can you upload SW , COMP and inductor current waveform for analysis?

best regards,
Edwin.

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TPS54821: TPS54821 issue