Re: ADC grounding
Also without knowing your circuit deails, I expect that at least the analog voltages have a common ground at the ADC. Thus the schematic doesn't probably apply to your circuit. Furthermore, analog and digital ground have often separate pins at an ADC, but aren't allowed to have large voltage differences (e. g. above 100 mV).
Manufacturer reference designs, if using separate power planes respectively split planes at all, are ususally connecting them near the ADC. Cause the supply voltages usually have a common ground at the power supply too, separate supply grounds allover the board don't make much sense then.