> This is interesting, and very important to me, as I usually pick up 7812's
> based on whatever's available and low-cost.  I have a ckt here feeding a 7812
> from 14.2V, and can't see which mfgr the part is from.  I've got 3 diff
> datasheets from National, Fairchild and TI, all which claim to be 2V.
>
> Can you please tell me which mfgr claims 3V?  It's important to me, so that I
> can avoid that one.  If I had to raise the input to >15V, at almost 1A, that
> would generate a lot more heat.

I know from experience that regardless of what the data sheets say, often
implementation is different than spec. More reputable manufacturers you
usually can trust (TI/National), but assume that everything is going to
give you problems. Don't run your designs so close to spec.  I've used
many 7812s from many manufacturers (TI, National, many no name brandes),
some claim 3 volts as an absolute minimum, some 2 volts as you mentioned
in a prior email, and even the low voltage dropout National voltage
regulators.

Sorry, but I'm not going to spend the time running back through data
sheets to find the specific one that says it needs 3 volts minimum to work
since it's a waste of time. Just because the data sheet says that it needs
a minimum voltage to work doesn't mean that it's correct under all
circumstances/loads, especially if it's a "low cost" 7812.

If you have the ability to adjust the voltage upward, you should do so.
And remember, the regulator will act differently under different current
loads.  But I can tell you from experience, if you're running it that near
the minimum acceptable voltage rails, you're asking for trouble. If you
turn it up to 16 volts, you may be burning off a bit more energy as heat,
but you are saving yourself potential headaches.

-->Neil

-------------------------------------------------------------------------------
Neil Bradley            In the land of the blind, the one eyed man is not
Synthcom Systems, Inc.  king - he's a prisoner.
ICQ #29402898

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