Can the ADuC702x be used with 3.3V on the analog inputs?
Internal Vref is only 2.5V
The max. input voltage for the analog inputs is specified in the datasheet
with absolute max ratings = AVDD + 0.3V (page 16 of the datasheet)
So if the part is operating as on the evaluation-board at 3.3V,
a 3.3V input to the analog channels is no problem - the part can't be damaged.
But you have to take in account that the internal Vref is only 2.5V, so every
measurement between 2.5V and 3.3V returns the max. ADCDAT value of 0xFFF = full-scale.
But you can use a external 3.3V reference to measure correctly as well the 3.3V input voltage.
In the absolute max. ratings the max. AVDD < = 6V!
But the specification for the part is only valid for the
operating voltage range from 2.7V to 3.6V (datasheet page 6)!
Does this mean you would simply connect the 3.3V rail to the Vref pin? And program REFCON = 0x00?