On Mar 8, 2007, at 10:21 AM, Markos wrote:
> The datasheet does not mention anything about the voltage
> reference max input voltage. If you see in "electrical
> characteristic",
> states that you cannot operate the device above 0.8V over VDD in IO
> pins:
>
> VIH Input High Voltage
> I/O ports:
> D040 with TTL buffer 0.25 VDD + 0.8V
>
> Thats all i've found about it, because in the ADC chapter doesn't
> mention anything about it.
Microchip (almost?) always lists an allowable range for the
external Vref input in the datasheets.
Which PIC chip are you using?
> So, to summarize it, If I divide the voltage, I loose resolution
> (inverse proportional). Same applies to the Op Amp, which will reduce
> the voltage too, but with higher part count and cost ;-)
...and accuracy, and input impedance. OpAmps are hardly expensive
these days.
-Dave
--
Dave McGuire
Port Charlotte, FL
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