TPS54320: powergood reset

zhang ping

Part Number: TPS54320

Vin=12V,Vout=1.05，Iout=2A,Iout max=3A,now PWRGD reset often,ripple is large,such as the picture,can you give me some advise about the design?

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

Zhang,

Can you post waveforms and your schematic?

0 zhang ping over 6 years ago in reply to JohnTucker

Genius 3835 points

0 JohnTucker over 6 years ago in reply to zhang ping

TI__Guru**** 191445 points

Zhang,

Pleas post two more waveforms:
Trigger on falling edge of PWRGD and show Vout and PH node, 5 usec / div.
Trigger on rising edge of PWRGD and show Vout and PH node, 5 usec / div.

0 JohnTucker over 6 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Zhang,

The loop has very low phase margin. That is your issue. Try:
PC8 = 470 pF
PC15 = 22 nF
PC12 = 47 pF
PR9 = 1.5 k

Let me know if this works for you.

0 zhang ping over 6 years ago in reply to JohnTucker

Genius 3835 points

There is no PC18 here. Please confirm it for me. Which pin connect ？and the Original value？

0 JohnTucker over 6 years ago in reply to zhang ping

TI__Guru**** 191445 points

Should be PC8, the feed forward capacitor (your schematic = 150 pF)

0 zhang ping over 6 years ago in reply to JohnTucker

Genius 3835 points

HI John
Thank you very much，use the value
PC8 = 470 pF
PC15 = 22 nF
PC12 = 47 pF
PR9 = 1.5 k
The ripple decreases and the PWRGD is normal. ripple is +/- 10mV。

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TPS54320: powergood reset