NRF52840 nRESET pin

RE: NRF52840 nRESET pin

Øyvind — Tue, 07 May 2019 07:49:57 GMT

Please see my previous answer. REG0 Output can be configured between 1.8V up to 3.3V using the REGOUT0 register.

RE: NRF52840 nRESET pin

Mike — Mon, 06 May 2019 17:48:24 GMT

Is there a way to set it so that it doesn't drop back to 1.8V during a system reset?

RE: NRF52840 nRESET pin

Øyvind — Mon, 06 May 2019 08:22:56 GMT

Hello,

You can read more about how to configure the power supply in the Power and Clock Management Chapter. The REG0 output is available in High Voltage mode, and configured in the REGOUT0 register.

Kind regards,
Øyvind

RE: NRF52840 nRESET pin

Mike — Fri, 03 May 2019 17:28:27 GMT

My mistake, it looks like it drops down to 1.8V before being initialized back to 3.3V. Is there a way to program it so that REG0 is permanently 3.3V?

RE: NRF52840 nRESET pin

hmolesworth — Fri, 03 May 2019 17:24:43 GMT

That sounds worrying, need Nordic Engineer input for this .. if Reg0 indeed goes to 0 volts, then the power for the core including the reset pin itself will disappear leading to a potential oscillating condition once the core recovers ..

The other issue with the reset pull-up is that extended shelf life is not possible by simply holding down a reset button as the discharge current is high given 13k pull-up resistance. I only mention this as I came across a case where the user was doing just that, taping down the reset button (not the nRF52840 though). They changed to system off with another pin used as wake-up.

RE: NRF52840 nRESET pin

Mike — Fri, 03 May 2019 16:43:34 GMT

Also, it seems that during reset the output of REG0 goes to 0 volts. We are using a battery hooked up to VDDH, I just want to confirm that this is the expected operation.

RE: NRF52840 nRESET pin

hmolesworth — Fri, 03 May 2019 01:40:23 GMT

Yes, the pull-up is enabled; I assume the pull-up value is about 13k (standard pull-up) as I never found a separate specification