We are using an AD7768 in our design and are observing some noise on the digitized data only when we have a common mode voltage greater than 0V on our input. For example, if I put in a sine wave centered around the CM voltage (1.024V), the sine wave is digitized perfectly. If I have a -100mV or +100mV DC-offset from the CM, I start seeing impulses on the digitized data the somehow relates to the sampling rate. The "impulses" are roughly ~175 Hz in fast mode (sample rate of ~16MHz), and ~22Hz in eco mode (sample rate of ~2MHz). Any idea whats going? The magnitude of the impulse varies with the DC offset. If it is 100mV, the impulse is ~15mVpp. If it is 500mV, the impulse is ~30mVpp. I have verified these impulses are not part of the analog input waveform or the reference voltage.