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ADC AD7656 disfunctions when operated fast

Question asked by keremcant on Aug 27, 2011
Latest reply on Aug 29, 2011 by clairec

I am using this ADC, AD7656. It says that it operates with 250kSpS. however when I operate it with 200kHz, it does not work properly.
I am using only two channels of the adc. When I increase the frequency of sampling, the second channel starts to output wrong values sometimes. Although it is connected to the gnd of the circuit, it outputs a very large value, around 64000, where the max value is 2^16=65536. But it does that for some samples; not all of the samples are corrupted, one out of 5 samples have high value, others are normal. And the frequency of corrupted samples increase with the increasing sampling frequency.
Any possible explanations? any help?