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From: "N. Coesel"
Subject: Re: Unusual latchup problem
Date: Wed, 6 Nov 2002 11:06:57 +0100
Organization: Planet Internet
NNTP-Posting-Date: 6 Nov 2002 10:08:27 GMT
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
"Jean-Rene David" wrote in message
> This is a circuit I didn't design but which I'm troubleshooting.
> It seems I have a latchup problem on a circuit with no connection to the
> exernal world. There are four supplies (+-12, +-5) but no part is
> to both (I removed them all) and no +-12V part is connected to any +-5V
> part. All the +-12V parts are opamps or instrumentation amplifiers.
> Now the symptoms are strange in the following way: when I fire up the
> supply with the circuit plugged in, the -12V latches up 90% of the time.
> When I turn the supply on and THEN connect it to the circuit, the -12V
> latches-up about 10% of the time.
I've seen similar problems with negative rail regulators. IIRC these where
79xx regulator series from ST. The problem was solved by connecting a 1k
resistor accross the outputs.
Reply to: nico nctdev nl @ .
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