Hi,

A couple of my BBBs have begun to not respond or intermittently not respond 
to the 5V supply, i.e. VDD_5V, but still are able to be powered through the 
USB. When in this state the board does not appear to respond at all to 5V 
power, no power or status LEDs. When I first noticed the problem I found 
that they would eventually return to normal operation if all power was 
removed for an undetermined period of time.


These devices are setup as remote systems that power up periodically via an 
external RTC, which momentarily pulls PWR_BUT to ground in order to turn 
the device on. They are powered through VDD_5V via a custom cape, as such, 
the error I’m seeing effectively breaks the function of my device.


I don’t know what’s causing this error, but assume that it’s something 
related to the PMIC. I believe I’ve only seen this issue on RevB BBB’s but 
the PMIC is the same for both the RevB and RevA boards that I have. I’ve 
also seen various levels of current draw from VDD_5V when in this state, 
~18.5mA in one case and ~0.39mA another time. I was wondering if the PMIC 
might be in some lockout mode, I know there is an “Under Voltage Lockout” 
mode. However, I haven’t figured out a good way to test this.


Any suggestions to help debug this issue would be greatly appreciated.


Thanks

jay

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