Recover from a brown-out reset

Question

Hi, 
 I encountered an issue from my custom board who are using a nrf52832. 
 When i place my board in very cold temperature environment (around -35°C), sometimes the voltage drop below VBor, that put my device in reset state. 
 My issue are the voltage could stay below Vbor during long time (>15min), and the consumption is around 1-2mA against 20uA in running state. That reduce considerably my life time of my device. 
 Is this consumption normal (i don't found any information about this) ? Is there is a way to reduce it ? 
 I see some devzone that explain the best way is to use the POF in order to put the system-off mode before brown-out are detected. My issue are how to wake up the device from the system-off when the voltage are not critical ? In other way, how to wake up the device without human action ? 
 For information the battery use is a CR2450 with operating temperature -40 to 85 °C. 
 Thanks, 
 Best Regards, 
 Julien

hmolesworth · Answer

Yes, classic repeated reset cycles. With no AIN available the only other option is just to repeatedly modify the POF threshold (Brown-Out detect level) and gradually lower this threshold on a reset or startup (as described above) to get a crude but effective VDD voltage comparator. Use a delay and perhaps also measure temperature; the temperature and POF (VDD) voltage can instigate a delay before the next POF check and only proceed when there is an acceptable level. cpu must be kept mostly asleep between these POF checks, of course; use a simple RTC timer for that. 
 " If the POF is enabled and the supply voltage falls below VPOF, the POFWARN event will be generated. This event will also be generated if the supply voltage is already below VPOF at the time the POF is enabled, or if VPOF is reconfigured to a level above the supply voltage ."