I am planning to have independent AGND and DGND ground planes in my system, and plan to short the two GNDs together at or under the ADC.
If I use the AD7915, would the bypass capacitors for VDD (2.5V power rail for ADC core) be connected to AGND or DGND?
Initially I would have thought it would attach to DGND, since it drives the ADC SAR structures and likely has some high-frequency digital content.
But I noticed in one of the packages that the VDD pin is placed right next to the analog IN+/- pins, and I know the pin layouts on these ADCs is derived to allow a AGND/DGND split across the part body center. This seems to imply that it would be better to bypass VDD to AGND…