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Reply-To: "fred bartoli"
From: "fred bartoli"
References: <email@example.com> <firstname.lastname@example.org>
Subject: Re: Why use resistors to tie a logic input to ground?
Date: Thu, 17 Oct 2002 16:44:38 +0200
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NNTP-Posting-Date: 17 Oct 2002 16:43:09 MEST
Tom Bruhns a écrit dans le message :
> email@example.com (Manvinder Bhullar) wrote in message
> > Hi All,
> > I'm looking at this circuit from Anchor Chips that shows unused inputs
> > of a 74LCX14 tied to ground with 10K resistors.
> > Can someone please advise what the rationale is behind this? I've
> > always tied unused inputs directly to ground. What role do the
> > resistors play?
> They're useful in automated test situations; the tester may "know"
> about the expected behavior of lots of parts and if (all) the inputs
> can be set by the tester, it makes testing easier. Of course, that's
> at odds with making compact equipment...and at least in my case, I can
> usually get the guy who writes the test software, after some
> grumbling, to accept a design with grounded inputs. (Actually he's
> nicer than that about it; he just points out that it limits the
> testing he can program, though not necessarily in a way that really
> matters, and I guess it is more work for him.)
I used to work for Alstom, building boards that travel in trains and such
Hard tying inputs was strictly forbidden on the assumption that it could
lead to non detected future field failures that would have been otherwise :
even if you don't use it, a dead input or gate is a bad sign for the future
life of the part.
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