ADS9817: Inquiry regarding output code fluctuation and stability issues on ADS9817

Part Number: ADS9817

• Analog Inputs (AIN1 to AIN8): All negative (M) terminals are tied to GND.
• Positive Inputs (P): Connected to the outputs of 8 individual differential amplifiers.
• Test Condition: For experimental purposes, the +/- inputs of the differential amplifiers are shorted together. Therefore, the output voltage from the differential amplifiers is 0V.

1. Behavior after Power-On:
   Immediately after turning on the power, there is almost no fluctuation in the AD results. However, when taking measurements a few minutes later, the fluctuations appear. The peak-to-peak amplitude worsens by a factor of approximately 10, and the data plots for all 8 channels overlap perfectly. Furthermore, the cycle of these fluctuations appears to be close to the power supply noise line frequency.
2. Cooling Test Results:
   To check for thermal effects, we used a spot cooler to cool down the ADS9817 while it was in the fluctuating state and took measurements immediately after. However, the fluctuations remained unchanged, suggesting that the issue is not caused by IC temperature rise.
3. Behavior after Re-initialization:
   While keeping the power on, if we execute the initial configuration settings for the ADS9817, the fluctuations immediately disappear. However, after leaving it for a few minutes, the fluctuations return when we measure again.