One perfect application for TL431 is replacing a few lines of code and
some comparators and/or AD inputs for monitoring precisely the PIC
supply value in portable applications. It's what I named "oldest but
goldest". Like LM723, ICL7107 and a few other components without age
and without aging.
:)
Vasile

On 6/10/08, Richard Prosser <rhprosser@gmail.com> wrote:
> Jinx,
>
> The TL431 is likely to be much more temperature stable than the LM7805
> and should be lower noise also.  Also much more consistent between
> samples.
>  I've used the TL431 several times and while it's not perfect, it
> meets my requirements over -10 to +70C.  Just use resistors with good
> temp coefficients!
>
> RP
>
> 2008/6/11 Jinx <joecolquitt@clear.net.nz>:
> >> Use the AD reference at 4V or so. Where do you get inexpensive 4V
> >> or so reference?
> >> TL431 or LM431
> >> Specifically, in any PC power suply there is one.
> >> How many do you have in your basement ? I think I have hundreds...
> >
> > I have access to thrown-out 48V Nokia PSUs and each one has a
> > control board with a dozen TL431. I haven't tried one as a voltage
> > reference source though. The 4.096V references I looked at were
> > a little expensive (although I didn't shop around), so I should include
> > a TL431 in the next round of experiments then
> >
> > Currently I'm using a jacked-up 78L05 to make 5.12V for Vref for
> > several boards. It's quite easy to set with a couple of fixed resistors
> > and a trim-pot. If I continue to use that it'll need testing to make sure
> > it's stable from say -10C to 40C. The case is heated a little by the
> > PSU so temperature probably won't go too low
> >
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