Lpc2000

The analog inputs and references look stable to me. No floating 
pins. I've made the Vin- input closer to ground:

Analog input (always +ve)---> Vin+ 
0V                       ---> Vin-
3V                       ---> Vref
5V                       ---> AVDD/DVDD

...but the same readings are still coming out. Maybe it's because 
I'm using a "true differential" ADC. I heard the setup's different 
compared to pseudo differential which I'm more accustomed to using.

--- In lpc2000@yahoogroups.com, "Kerem Or" <k.or@s...> wrote:
> It appears there is a common mode voltage problem. Check if there 
is a 
> current return path between AIN-/AIN+ and AGND. What you observed 
can happen 
> if the signal source is floating with respect to AGND. As you have 
noted the 
> AD accepts -2.5V to 2.5V. But since the part is not bipolar, the 
applied 
> input signal must not be above VCC or below ground with respect to 
AGND. 
> i.e, -2.5V actually means 0V connected to AIN+ and 2.5V connected 
to AIN-. 
> It is not -2.5V with respect to AGND.
> 
> Just make sure voltage on any of the differential pins is in 
between the 
> part's common mode range.
> 
> Kerem