Brown-out (or Power-On-Failure) detection in low voltage mode setup (supply is 1.8V)

[Michal Zacharias]

Hi, everyone. I would like to be notified about the brown-out on my device. I know about POF peripheral, but lowest possible threshold is NRF_POWER_THRESHOLD_V21 (which is 2.1V). I'm using low voltage mode on my device, which means the supply power is always 1.8V and therefore always lower then POF threshold. Is it possible to use POF with low voltage mode?

[Stefan Birnir Sverrisson]

Hi Michal

It is not possible to detect with POF a declining supply voltage under 2.1V. 2.1V is the lowest voltage setting for the POF. The POF is meant to detect falling battery voltage which is typically ~3V when fully charged.

The brown-out-reset is specified to reset the chip when supply voltage drops below 1.7V and will hold the chip in reset mode until supply voltage again exceeds 1.75V. When coming out of reset, code execution will start from the beginning of your program. You could check the NRF_POWER->RESETREAS register in order to detect what caused your reset.

To monitor supply voltage drop, you could use the internal ADC.