AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Steven Hodge" <stevehodge@...> 
wrote:
> In fact, nowhere in the main text of the ADC section of
> the data sheet does it explicitly state, or even imply
> that Vref cannot be greater than AVcc.  
Perhaps so.  But in the section titled "ADC Characteristics" (way in 
the back of the datasheet) it clearly specifies that Vref may not be 
larger than AVcc and, in the same table, it specifies that AVcc 
must be within 0.3V of Vcc.

Moreover, in the "Electrical Characteristics" section in the box 
entitled "Absolute Maximum Rating" it clearly says that no pin 
(other than RESET/) may have a voltage applied greater than Vcc + 
0.5.

You'll most likely have to use a voltage divider to ensure that your 
analog input voltages remain below the maximum level.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net