nRF52810 Power Up Issue

[Harv77]

Can a "Pin Reset" recover the nRF52810 part if the part has encountered a slow voltage rise, greater than 60 ms, from 0 - 1.7V (described in the image below)?

[Simonr]

Hi

Why are you planning on having this slow of a voltage rise? Yes, you can recover it manually after the slow voltage rise by applying a pin reset or power cycle to avoid it from hanging during the Power On reset.

Best regards,

Simon

[Harv77]

We are running the nRF52810 with a coin cell battery and a super capacitor. The coin cell charges the super capacitor slowly, so the rise from 0 - 1.7V is VERY slow (could be up to 60 seconds). We have a stand alone supervisor chip connected to the nRF52810 RESET line. The supervisor chip holds the line low until the input voltage reaches 1.9V. The line is then released.

The issue is when the supervisor chip reaches 1.9V. The RESET line is held low (0V) up until this point. The line is then released and should rise to the supply voltage (regulated to 2.5V). I'm seeing the RESET line at around 0.3V after the supervisor chip releases the line. It seems like the nRF52810 is stuck in strange state at this point. We've tried manually toggling the RESET line, by shorting it to ground in this state. This does not get the part to reset and run normally either. Is there something I'm missing here?

[Simonr]

Hi

I spoke to one of our experts on the matter, and unfortunately this is the expected behavior, as the chip will need a valid POR event before being able to reset as you want. As the pin reset is configurable, the SoC won't be able to set it up correectly without a valid POR first. So the VDD rise time is a requirement I'm afraid. A possible solution might be to connect the supervisor chip to a MOSFET that delayed VDD until it is high enough.

Best regards,

Simon