nrf52 reboot and VDD overvoltage

[pytepaul]

Hi,

I am trying to figure out the reboot reason on an NRF52 in order to solve it in the best way.

We have a design with a dual supply 3.6V/5V going through a 3V LDO. Problem is that when swtching from the 3.6V to the 5V one the LDO reacts in a slow way and it results in a 3.8V over-voltage for 200us on the NRF52 supply until the LDO regulates to 3V.

To my mind this reset may have to deal with the brownout reset has at reset powerup RESETREAS register is printf-ed and it contains 0x0, while it was set to 0x1 at previous startup. So this register has been reset too. And only a power on or a brouwn out reset clear it.

As additional information, the design is based on a BMD300 Rgado's module.

Thanks for your help, Paul.

[John]

Did you see this note in the power section of the product specification: "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."?

There doesn't seem to be a category in the RESETREAS that covers this case so perhaps that is why the value is 0?

[pytepaul]

Hi John,

I think you pointed out the explanation. We are in the >=300mV in <=300ms case. As this generate a power on reset, this also reset the RESETREAS register. So I have to reduce the overvoltage to something at least below 3.3V.

Thanks for your answer, Paul.