Managing nRF52832 with a 3,7V Li-Po-battery

[Ray Breslin]

Hello,

I am currently evaluating concepts on how I can power my nRF52832-custom-board with a LiPo-battery, in order to get a good tradeoff between lifetime and form-factor.

First of all, I came across this topic here, that states to never use a 3,7V-Li-Po-battery directly as power-supply due to its maximum voltage of 4,2V when fully charged. As far as I know pretty much every Li-Po-battery has a 4,2V-level at its charged-state, but only as long as there is no power-consuming-circuit attached. If you connect a component that draws current, then the voltage-level will immediatly drop from 4,2V to 3,7V while being in operation-state (open to corrections here!).

Now even those 3,7V exceed the recommended operation-conditions for the nRF52832, so I assume there needs to be some kind of regulation circuit integrated. Is it better to use f.ex. a 3,3V-voltage-regulator like the NCP161 or can you use just a simple shottky-diode/hot-carrier-diode with a 0,2V-forward-voltage? What about the suggested Torex XC9265 PFM-module (see link above) - does anyone have any experience with that?

Kind regards,

Ray

[Jørn]

Hello Ray Breslin

Please note the ADC's of the nRF51 and nRF52 do differ in a few aspects, so be sure to read through the SAADC section of the nRF52832 product specification here.

You can find a SAADC example in the SDK->peripheral->saadc folder (SDK11 and later). The example you refer to is outdated as it was made for SDK 6, which was released several years ago. I recommend you look at the examples of newer versions of the SDK.

For the resistor divider you will need to set the acquisition time (described in the PS linked above) to a suitable interval, based on the total source impedance of your divider.

Another relevant read is this blog post on battery voltage measurements with the nRF52

Best regards

Jørn Frøysa