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PMP8861: Can't get the reference design stable.

Part Number: PMP8861
Other Parts Discussed in Thread: LM5025, UCC2897A, TL431, TLV431


I used a PMP8861 reference design because it is basically the solution we need. We have made our own PCB with it but I can't get it stable.

This is the OUT gate signal for the main FET.

I have also measured the FB(Blue) and VREF(Orange) pins.

VREF is pulled to 0V by FB. I can't find where in the loop the error comes from. Any ideas?

I have previously tried something with a LM5025 design and I had a similar problem (gate signals FET). Never have been able to solve that either.