Re: Bizzare behaviour from SG/UC3525

Tony Williams wrote:

> In article <42B940A2.3014FE0F@xxxxxxxxxxx>,
> Pooh Bear <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:
>
> > Actually I thought 0.1uf was a bit big so I added 10nF there. It
> > had the desired effect you suggest.
>
> > It seemed to stop the 'jitter' on the trailing high side edge but
> > then I went and switched the damn thing off and the IR2110 went
> > Fizzzz as the rails decayed ! And it was the the *low* side
> > driver that had gone bad ! It measured 2 ohms form Vs to out
> > after this incident !
>
> I don't seem to see complete threads these days, so
> apologies if this remark is out of date.
>
> Perhaps point your bifocals at the 3525 UVLO, and
> think about whether it is coming in too late, (on
> power-down), and is not making the output stages safe
> before the main supply rails drop to a damaging
> undervoltage.

Yes, I looked at that area. I'm unhappy it's adequate so I'm intending
to add my own over-riding UVLO that monitors all the rails.

In the instance I mention however I had already asserted the shutdown
function on the 3525 before allowing the rails to decay - i.e. OutA and
B were both inactive. Then the IR2110 expired as the volts dropped !

Graham

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