ADC AD7682 have digital SPI connection but no digital grounding specified in the package.
As per datasheet " At least one ground plane should be used. It can be common or split between the digital and analog sections. In the latter case, the planes should be joined underneath the AD7682/AD7689."
How to connect the digital ground with the ADC package (if any potential differences in the grounds, how it can be compensated)?
I connected the Analog ground for the provided ground pins.