Hi Jim, Hard to say exactly what might be going on without getting into the circuits and measuring various points around the diff amp and ADS1247 , but I suspect slight differences in the ground potentials are the reason. Have you measured the difference between the two AVSS pins? Having the two sections powered from different 3.3V sources is OK, but the analog input circuitry has to be referred to the same ground potential as the ADC. When running these two devices with a single supply, both AVSS pins should be tied together through a low impedance connection.
↧