nRF52832 battery powered rise time issue

[OllieJ]

Hi all,

We are running into a problem with our battery powered nRF52.

The nRF is continuously powered by one lithium cell. When the battery is very deeply discharged (e.g 1.0V), the nRF is in reset state because of BOR. When we slowly recharge the battery, the supply rise time is much longer than the specified max 60ms.

The problem is that the POR circuit of the nRF52832 does not work properly with such a slow supply rise time. Is there something we can do about the configuration in software or is it only solvable in hardware?

Thanks!

[Turbo J]

OllieJ said:

one lithium cell. When the battery is very deeply discharged (e.g 1.0V),

... the cell is dead and could possibly set itself on fire.

Li-Ion cells absolutely require a deep discharge protection circuit, which would also somewhat solve the POR problem.

[OllieJ]

We are aware that it is not allowed to discharge so deeply but in our application it can happen very very occasionally when misused.

I guess that there are also applications with NiMh packs that will be fully discharged. How to solve the POR problem in those applications. Is it only possible in hardware?

[ketiljo]

You need to apply a pin reset or power cycle the device in case it hangs in POR. 

But as Turbo J say, discharging a lithium cell this far is potentially dangerous so  you need to add low voltage protection. 

[OllieJ]

So it's only solvable in hardware. Unfortunately we have to add an own POR circuit.

Thanks!