I have some problems with my ad7357-eval kit. When I input an AC signal to the corresponding pins Va or Vb the signal seems to have a drift of ~0.2V. For example if the input is 0 - 0.6 AC (e.g. from AD9837) it becomes 0.2-0.6. This error is quite weird and I have tried with 2 different evaluation kits with the same result. The only change I made to the kit is removing the S24 and S19 jumpers so that the ADC is not terminated at 49.9 Ohms. The tests were made both with a CED1Z kit and with a custom interface using a Pi with the same results. Do you have any suggestions? And another quick question just to verify the setup. In order to utilize the ADR421s as voltage refs I should just close S21, S23, S13 and S16?
Thank you in advance,
Lefteris Kampianakis, PHD at UW