I have a similar issue than explained in post AD7656 power supply anomaly.
In short, the V_drive pin is driven by a 3.3V Voltage Regulator (LD1117). However after power up, that pin shows around 4V. Believing the regulator was damaged, it was removed and the ADC was powered up again. This time it showed around 4.5V. The regulator was tested and still works fine. This issue was seen in two chips already. The rest of the chip seems to work fine.
Reading through posts, the cause might be the power up sequence, what would be the right one? So far, the VDD and VSS were driven first and AVcc/DVcc and VDrive were driven second.
I ask the question again because the thread posted formerly had no answer.
Thank you very much for your help in advance.