On Tuesday 17 July 2007 12:30, Steve Smith wrote:
> I think its doable with just an output pin...
>
> 1.	arrange the ratio metric input to be 75% FSD or 3.75v or some value
>
> >2.5v and ensure its got about 1mA available. (this is to ensure the
>
> programmable zener works properly.)
> 2.	Arrange TL431 or equiv across the low end resistor. They are 2.5v
> with the control pin high z.
> 3.	connect the spare pic pin to the 431 control pin (may need a
> resistor) set output low and tris controls the voltage ref either 2v5 or
> supply voltage over ??
>
> Steve


Hmmm... TL431 with a control input you say, huh?  I'll go investigate...

Cheers,
-Neil.
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