On Sunday 27 April 2003 08:32, Neil Bradley wrote:
> I know from experience that regardless of what the data sheets say, oft=
en
> 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 mentione=
d
> 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 w=
ork
> since it's a waste of time. Just because the data sheet says that it ne=
eds
> 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 curren=
t
> loads.  But I can tell you from experience, if you're running it that n=
ear
> 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 hea=
t,
> but you are saving yourself potential headaches.
>
> -->Neil

Well, buffers and extra overhead is fine, but every volt I add to the inp=
ut,=20
while running at close to a full amp, adds an additional W of heat to be=20
dissipated, so I'm trying to optimize this as much as possible.  And with=
 the=20
10% tolerance of the device using it, I think I've got a good buffer alre=
ady.

Cheers,
-Neil.

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