nRF52840 Coin Cell Battery Percentage Monitor

[Radio]

Hi All,

I want to measure the battery level in my nRF52840 design using the ADC.

I came across this thread in the nordic devZone https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/measuring-lithium-battery-voltage-with-nrf52

My questions are,

1. In the voltage divider diagram shown in the above  thread, AIN connected to the ADC input. I presume, the sane AIN should be connected to the VDDH pin of the nRF52840 chip to power up. If that is the case, when ADC starts to sample, will it affect the overall power supply to the chip?

2. Are there another way of measuring the nRF52840 battery level especially for an industrial design? 

3. Is there is a way internally I can measure the VDDH pin battery level?

Thanks! 

[Radio]

Further to my above explanation, I am planning to use a CR2032 battery in my design.

I also came across Thingy52 schematic. In there they use two MOSFETS as shown below. Any comments on using the below circuitry in nRF52?

[Jared]

Hi,

1. The AIN should be connected to the ADC in the nRF52 through a AIN pin.
2. The battery monitoring in the Thingy:52 is a viable alternative. The Thingy:52 is as the name suggests already using a nRF52832.
3. No, unfortunately this isn't a feature of the nRF52. 

regards

Jared 

[Radio]

Hi Jared,

Many thanks for the reply. In the Thingy52 battery circuit above:

1. Should I connect "VLi-Ion" pin to the VDDH pin of the nRF52?

2. Is it recommended to use a voltage regulator before connecting to the VDDH pin?

3. I see a voltage regulator in the Thingy52 circuit, but some say not required for nRF52. But in this case since I am having a battery monitoring circuit, should I have a regulator? 

Thanks!

[Jared]

Hi,

1. The VLi-Ion pin should be connected to your supply i.e your battery
2. No regulator external regulator is needed.
3. It depends on the voltage of the battery that you're using. The nRF52832 has a maximum recommended voltage of 3.6 V. Anything over would need a step down regulator.

regards

Jared 

[Radio]

Hi Jared,

What about the chip power supply pin? VLi-Ion should be connected to this as well right?

Thanks!

[Jared]

Yes! The battery should be connected to VDDH(if using High voltage mode). 

[Radio]

Thanks for the information!