nRF52840 Battery voltage measurement in normal voltage mode

[PabloL]

Hi,

I want to measure the battery voltage with my nRF52840 board.

According to the datasheet VDDH should be shorted to VDD to normal voltage mode. (Circuit 1) So, in order to measure battery voltage, it is necessary to use a voltage divisor connected to an ADC input, which draws current all the time.

To take advantage of internal voltage divisor VDDHDIV5 it is necessary to connect VBAT to VDDH, so:

Questions:

1) Is it possible to connect VDDH to a higher voltage than VDD keeping the normal voltage mode (REG0 off)? (Circuit 2)
2) If correct, will the internal ADC draw some current from VDDH when it is disabled?

In both cases there is no inductor on DCCH.

Thank you!

[ketiljo]

You can make a very low current voltage divider like this:  https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/measuring-lithium-battery-voltage-with-nrf52 

Circuit 2 won't work.