AVR-Chat

Dave VanHorn wrote:
>>Were you attempting to use this non rail-to-rail clock for 
>>external devices?
> 
> Absolutely not.
> 
>>As I undersand that data sheets on this issue, the low power 
>>(non rail-to-rail) clock option is only recommended when you are NOT 
>>sharing the clock wqith any other device.
> 
> I've confirmed with Atmel that it's a Vittoz type oscillator.
> Pull a google on it.  Nice way to save power, but your crystal 
> selection is much more critical. Notice that Atmel gives you no 
> guidance on what the amplitude should be, or really even that there's 
> much 'special' about this mode at all?
> 
> This issue forced us into a total recall of a bunch of systems. 
> The problems were glitchy, hard to pin down, and blamed on software 
> and hardware, up until a new date code of AVR chips arrived, and at 
> that point, some fairly large number of them wouldn't start, using 
> the same crystal and caps as we had before.

There's no such thing as a Vittoz oscillator. All Vittoz did was
derive some conditions for a standard oscillator that has always
existed and that i've analysed and figured out eons ago. What he
hasn't done is derive the optimum conditions for large-signal
operation;)