Howdy Jinx,
(cautiously not using any other words that may sound like "hijinks" :-)


On Thursday 08 May 2003 22:08, Jinx scribbled:
> > But there is a chance that the device may be powered on without
> > the sensor being connected, and this would send the A/D input
> > pin to Vdd.  The datasheet states a maximum of +2.8V (Vref +
> > 0.3V) on this pin.
>
> You're referring to parameter A25 wrt RA3 ?

Yep -- Param A25, Sym VAin, on page 136 of ds30221B.  Table 14-9: A/D=20
Converter Characteristics.  I don't see any reference to this being speci=
fic=20
to RA3, though.


> Doesn't this mean if you're using RA3 as Vref+ then RA3
> cannot be used as an i/p ? And that the maximum voltage it
> could be (inadvertently) exposed to is Vref+ +0.3V ?

In my ckt, RA3 is fed by a 2.5V reference, with ADCON1 set to xxxx0101 (2=
=20
channels, 1 external ref).  The sensor input is on AN0.

(I definitely assume than any pin used for an external ref cannot be used=
 as=20
an i/p.)

I interpreted param A25 to mean "The input voltage on *any* analog input =
pin=20
(except those used for external Vrefs) must not go less than 0.3V below V=
ss=20
and must not go higher than 0.3V above Vref+".

Cheers,
-Neil.

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