AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Graham Davies" <YahooGroups@e...> 
wrote:
> --- In AVR-Chat@yahoogroups.com, "Alexandre Guimaraes" 
<listas@l...> 
> wrote:
> 
> > > > Yes, it is successive approximation, at something like 200 
kHz.
> > > You can go up to 1MHz if you only need 8 bit precision.
> > That makes it even more interesting.... 
> 
> Just to clarify for anyone not reading the data sheet, these 
> frequencies are the SAR clock rate. Conversion takes 13 cycles. So, 
> the fastest sample rate is about 77 kHz. The input bandwidth is 
given 
> as 38.5 kHz, which is exactly half this and should probably be 
taken 
> with a pinch of salt. It would be wise to limit the bandwidth of 
any 
> applied signal to this figure to avoid aliasing. I'm sure there are 
> more severe restrictions if you're switching inputs.
> 
> Graham.
> 
> P.S. The above is actually from the ATmega16.


OK, so if you wanted to monitor an analog value, an external ADC 
would be best if the speed of the samples were high.

as for the successive approximation, would the accuracy be higher if 
the process were relatively steady and the change between readings 
were rather small ?

Temperature is a very slow moving process so one would not expect to 
see a process swing of more than a few percent over a few minutes.  
So, would that mean internal ADC readings would be pretty accurate ?

Dave