We have a custom design that uses the i.MX6UL processor that is having an issue on about 1% of our boards. The issue is that when we send a poweroff command, the board reboots instead of powering off. We have made some measurements and have noted two odd behaviors on the failing boards. The first odd behavior is that the ONOFF signal (which in our design is only connected to a test point) droops causing SNVS_PMIC_ON_REQ to go back high, resetting the board.
We tried adding an external pullup of 1K to ONOFF, which eliminated the droop, but SNVS_PMIC_ON_REQ still went back high rather than remaining low.
The second odd behavior is that when we heated the failing board to try reflowing things, it started working properly for a few minutes until the board cooled off again, at which point the issues came back.
Any insights into what could be causing this behavior would be greatly appreciated.
