I have a customer that is looking at voltage rail behaviors in their design on startup and turn-off. In trying to understand the rail dependencies in the AD9371 they looked at the rails on the ADRV9371 development platform. Below is the waveform they captured:
and
The sequencing matches our prescribed sequencing, but the 3.3V rail is starting to pull up before being enabled. Is this due to internal interactions in the AD9371, or external circuitry? In looking at the schematic for the demo board I do see where the 3.3V rail is connected to level shifters ADG3301 and ADG3304 along with the VDD_IF rails. These parts seem to allude to an ability for leakage from VDD_IF to 3.3V rail if 3.3V rail is low.
- On the demo board what is causing the 3.3V rail to start to ramp up prior to enabling?
- Do we have a list of rail dependencies if not sequencing correctly? I have read that incorrect sequencing is not damaging, but do we have something that shows which rails will be biased up if other rails come up first that we can provide to the customer?
