We have acquired AD7682: 16-Bit, 4-Channel/8-Channel, 250 kSPS PulSAR ADC Evaluation kit along with EVAL-CED1Z.
At first place, I am trying to measure DC voltage. I found that if I apply regulated DC supply (1V, 1.8V,and 3.3V) to ADC input channel (say channel-0), I can see the correct measured voltages on my computer screen using the provided software.
However, when I provide the voltage (DC ensured) other than the regulated voltage I am observing incorrect voltage measured by ADC.
e.g., Applied 777mV DC wrt ground (from the same board from where I applied regulated supply previously), observed 1.88V DC.
Also, I can see that 2.5V is present at the 'input' channel of the ADC when it is kept in 5V reference range (when no external voltage is applied to ADC).
What can be the problem?