ADS7924: Power up sequence

Shoo,

The best place to look for information regarding supply requirements is in the absolute maximum specification table.   Reviewing the table you can see the following:

1. It is important to keep the input signal less than the AVDD supply (circled in red).  This means that you cannot apply any input signal before AVDD is power up.  It also means that you cannot go above AVDD by more than 0.3V or below ground by less than 0.3V.
2. Digital signals also cannot be applied before DVDD is powered up (circled in green).  Similar to the analog inputs the digital signals cannot go above DVDD or below GND by more than 0.3V.  Note that the open drain devices (SCL and SDA), can tolerate up to 6V input regardless of the DVDD.
3. AVDD >= DVDD (circled in blue).  From a practical sense this means that AVDD should be powered first then DVDD should be powered.  Of course, you could power them simultaneously, but it is possible that DVDD may ramp faster so you need to take care to make sure that this doesn't happen.
4. There is no specific power up timing, but in general very slow ramping supplies or nonmonotonic supply ramps (e.g. brown-out dips) can cause problems for many different types of devices.

Best regards,  Art