> I have a design whereby I want to sense the presence or absence of a
> voltage that is well above +5V; maybe up to 15V, say.  This voltage
> could be negative as well, at least until the user figures out they have
> their DC input backwards...
>
> I also want to use A4 to switch a pfet, and when the pfet is not being
> driven (i.e. A4 set to high, i.e. floating) it will be pulled up to 9V
> or so through 100K.

Hi Jesse,

If you use a big enough series resistor you can do the first one directly.
I'd say 220K.

The second one, I'd say no way. With earlier parts (16C54, 16C71) you
could switch 12 volts with RA4, but the newer parts are not so tough with
regards to voltage and RA4 is probably leaking badly even at the rated max
of 8.5 volts - I would feel safe using it up to 6.5V but no more.

Cheerful regards,

Bob


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist