Q: Are there special grounding considerations for the AD7606?
A: At least one ground plane should be used. It can be common or split between the digital and analog sections. In the case of the split plane, the digital and analog ground planes should be joined in only one place, preferably as close as possible to the AD7606/AD7606-6/AD7606-4. Multiple connections are acceptable as long as you ensure that there are enough connection points to mimic a solid GND plane. More details can be found on the Layout Guidelines on Page 32 of the AD7606 datasheet.