TPS65131: Negative output has some fluctuation

user6428223

Part Number: TPS65131

Tool/software:

Hello supporter,

I need some advice to get a stable operation on negative output of TPS65131.

Positive output is fine but negative output has fluctuation (seems like resonant) from time to time..

Target negative output voltage is 13.7V in my design, so one of feedback resistance is chosen 88.7kohm

instead of 121.2kohm on TPS65131 data sheet.

I selected feedforward capacitor, 7.5pF, based on TPS65131 data sheet.

Should I change feedforward capacitor ? Or what should I do to make stable operation in my design.

I appreciate any advice from you.

Best regards,

H.Yamai

0 Patrick Yao 6 months ago

Hi Yamai,

Do you have captured any waveforms? And you can try removing the feedforward cap.

Patrick

0 user6428223 6 months ago in reply to Patrick Yao

Hi Patrick,

Thanks for quick response.

Here is negative output waveform with/without feedforward cap.

It seems going away fluctuation after removing feedforward cap.

Can I think this is a solution ?

Best regards,

Yamai

1) with feedforward cap.

2) without feedforward cap.

0 Patrick Yao 6 months ago in reply to user6428223

Hi Yamai,

Yes, the feedforward capacitor is used to adjust the loop performance, it can be removed.

Patrick

+1 user6428223 6 months ago in reply to Patrick Yao

Hello Patrick,

I got it, thank you so much.

Best regards,

Yamai

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