Power on Reset about voltage

[BEN_HB]

Hi.

setup is 52832, S332, SDK 15.3.0. 

issue is about reset voltage.

I use CR2032 for power supply. 

repeat fast put on and put off CR2032 on custom board, sometimes adc value is strange.(mostly it is normal)

it value is too low. Coin cell is 3.0, but adc result is 2.2 or 2.3 (sampling 100 count, interval 1ms, average samples)

I checked adc value, it sampled 2.6~1.8V value.

So I Found on PS under below

"A step increase in supply voltage of 300 mV or more, with rise time of 300 ms or less, within the valid supply range, may result in a system reset."

1.In this sentence. when only increase step, may result system reset? If with 300ms or less time, step decrease in supply voltage of 300mV or more, Does not may result system reset?

2. Brown-out reset. it is under 1.7V, Does it happend? not configure manually?

Thank you.

[Kenneth]

If you suspect that it is the impedance in your coin cell battery that is causing the variation in measurements, then I suggest to connect a steady power supply for comparison. For most accurate measurement I recommend to start the external HFCLK (32MHZ xtal), do an offset calibration of the SAADC, before measuring measuring VDD (NRF_SAADC_INPUT_VDD) with internal reference (likely you also should set NRF_SAADC_GAIN1_6).

Your questions is not related to your SAADC measurements, but to answer them:

1. Yes. So for instance if you swap power supply from 2.6V to 3.0V this may cause a reset.

2. Brown-out reset will occur if VDD fall below operation conditions (<1.7V), the BOR occurs will ensure the chip reset before the chip can malfunction. This is not configurable, but fully handled in hardware.