My customer ran into an issue with the AM5748ABZXA getting stuck after being operated at a high temperature during testing
2 out of 10 units were observed to have this issue while chamber testing.
- At high junction temperature (> 133C) Processor would reboot -> go to uboot, try to run Linux, reboot and the cycle continues forever until temperature is lowered then the loop is broken
- If the unit is left in this rebooting cycles for too long ( > 1hour or so), it will eventually stop rebooting and get “stuck”
- When it is stuck, lowering the temperature will not revive it, i.e. it will not reboot anymore
- Even after setting the ambient temperature around AM5748 to room temperature for 2 days, manually resetting the AM5748 cannot boot it up (which also issues a power-on-reset)
- I made sure that power-on-reset is applied during my troubleshooting
- When I manually reset it, the soc didn’t issue a reset_out
- The only thing that can revive it is by doing a power cycle (removing power and applying power)
What has been checked:
- Sysboot pins are at correct level the whole time the unit is “stuck”. So when manual reset is applied, the straps are at proper level
- Clock input is present and correct
- PMIC got reset and PMIC went out of reset (it releases power-on-reset) indicating that all voltage output are good
I also noticed that the soc has an internal watchdog (WD_Timer2) that should kick every 3 minutes during booting if system fails to boot i.e.: if it fails to find a device to boot from or if it can’t execute image.
However, I didn’t see this 3 minute interval during this “stuck” condition.
I don’t think I can use a JTAG debugger for this issue since this issue occurs very early on in the booting process (in the ROM startup/initialization sequence).
I would like to know of what is happening and where it is stuck at in the booting process.