AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Graham Davies" <Yahoo37849@...> 
wrote:
>
> --- In AVR-Chat@yahoogroups.com, "Steven Hodge" <stevehodge@> 
> wrote:
> 
> > Can I ... input to Vref a voltage
> > reference value equal to the maximum
> > of what I need to measure, say 15 V,
> > even though that is well above AVcc?
> 
> No.
> 
> > Or does the spec "maximum" truly
> > imply that Vref cannot, under any
> > circumstance, be > AVcc?
> 
> Yes.
> 
> > If so, does that mean the only
> > solution to my problem is an
> > external voltage divider? 
> 
> Yes.  Is that so bad?

Just additional current drains of the order of what the uC consumes 
(especially as I will need to have 3, maybe 4, dividers).  However, I 
only need to sample very infrequently (like every second) so I could 
use mosfets and another output pin to turn on the dividers only when 
needed.

Thanks for clarifying things.  Steve