Yep. Data sheet says 2.4 to 2.8V.
Just been looking at the bandgap reference in the mega88. 1.0 to 1.2V. Pretty much useless as a true reference! We're having to use the power supply as a reference and calculate the error on the bandgap reference before calculating any measured input voltage.
Dave Pallant
AVR-Chat@yahoogroups.com wrote on 22/08/2005 19:05:42:
> Am a bit disappointed in the accuracy of the internal 2.56 volt
> reference used by the A/D converter. Have a nice 3.3 volts on the
chip
> supply. A 0.1 uF ceramic cap across AREF and GND. Nothing connected
to
> AVCC.
>
> Working the math backwards agrees with the voltage measured across
the
> 0.1 uF capacitor, that my reference voltage varies from 2.44 to 2.60
on
> different units.
>
> Is this typical?
>
> --
> David Kelly N4HHE, dkelly@HiWAAY.net
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