On page 26 of the ADA4254's datasheet (Power Supplies chapter), we can see that both the low voltage analog stage and the digital side must share the same voltage. The few applications I could find directly connected AVSS and DVSS together.
However, our entire system sits 2.5V below the ground level and we provide our analog side (-2.5 to 2.5V) and digital side (-2.5 to 0.8V) with two separate power supplies. Both are referenced to the same ground plane but the -2.5V levels are generated separetely. Here are our three questions:
- We are guessing that everything should be fine once steady state on both supplies is reached and the IC would be correctly biased, even with no direct connection between the two -2.5V. Is that a correct assumption?
- How much leeway between AVSS and DVSS 's voltage levels do we have?
- Can we expect issues during the transitory stage wherein AVSS and DVSS don't reach -2.5V at the same time? Do we need to cascade our power supplies? Do we need AVSS or DVSS to reach a lower voltage first?
Let me know if you need additional information to answer the questions above.
Thank you for your answers!