n51822 Brown-out reset voltage and duration for working

[Leo]

Hello,

I'm testing n51822 with low voltage mode, and want to check the BOR condition.

1. Is there any threshold for brown-out reset, or voltage tolerance? e.g. 1.68V or 1.72V
2. how long time is required for the ROR action? e.g. xx us lower than 1.7V

Thanks.

[Stefan Birnir Sverrisson]

1. Yes, the brownout is specified to put the chip in reset mode when supply voltage goes down to 1.7V. The chip should come out of reset again at 1.75V for low voltage mode configuration and at 1.80V for LDO mode configuration. I am not sure about the actual tolerance but I have tested this on a few nRF51 devices with noise up to 100mV peak to peak on the supply voltage, and the chip went to Brownout in the range of 1.64V-1.68V. For LDO mode, the supply voltage is specified to be 1.8V minimum and for Low Voltage Mode it is specified to be 1.75V minimum so there seems to be a good margin there.

2. I do not think this is explicitly documented how long you need to hold supply voltage low in order for the nRF51 to enter brownout reset. However, it is expected to be much shorter than any realistic supply rise/fall time.