Solved ignition noise problem...thanks all!

[Orin Eman]

> On Thu, 14 May 1998 17:48:12 -0700, Sandy <sganz at wgn.net> wrote:

> >Great, the LM2935 is slated for death, it is not recommend for new designs,
> >but the problem is that the Switch/Reset lead was acting as an antenna and
> >shutting down or glitching the main power for some reason. Get the 3
> >terminal LM2940-5, it is the automotive equiv. of the 7805 and has better
> >specs. like the LM2935. Keep us posted.

> Gee, I hope you're right Sandy, but I gotta tell ya I thot about this a
> couple times today, it just popping into me brain, I strongly suspect
> that the 2935 wasn't failing or being reset by lead noise, but rather
> was doing what it's supposed to do, which is shut down and pull down the
> reset line, IF it sees one of the several fault conditions it's got
> internal protection against. For example, as you well know, you don't
> carefully bypass and protect an IGN or INJ driver, say, and it easily
> will put what looks like a load-dump phenom to the 2935 on the +12V. If
> that puppy sees ANY transient on the supply lines above say 60V, which
> it's easy to do with stray IGN or INJ driver noise, it HAS to think the
> ALT has gone berserk, and WILL shut down and yank on the reset. It's

I had a bad time ever getting the EFi332 board OUT of reset
with the BDM connected.  The (LM2925 in this case) reset output
can't take hardly any load!

For my own designs, I use a 1N4004 in series with the power then
a 27V transient suppressor in parallel with a few hundred uF.
This cuts out a lot of the nasties before my regulator which
is a regular 7805.  A low dropout regulator would be better
since I eat almost a volt with the diode.

Orin.