I'm using a NRF52832. I'm looking to measure the battery voltage. I'm using 2XAAA cells in serie (voltage range between 2V and 3V).
Below is the configuration to measure the voltage (To simplify the example, I have voluntarily removed protections on the battery connection).
Regarding the internal characteristics of the ADC on NRF52, what is the best value for R6 and C6 to avoid any issue with acquisition time / impedance ...? Could you confirm that the leakage would be very low (input impedance >1M Ohms on the ADC input)?
EDIT : In my real use case, the NRF is not directly powered by the batteries but by a boost circuit (3V).
I assume you are actually powering the nRF with the 2xAAA batteries, if so there is no reason to provide an external connection to the batteries. You can configure the SAADC to measure the nRF VDD via its register settings. It has internal hardware connections to VDD to facilitate this.
Thank you for your reply.
I have over simplified my example regarding the real schematic. In my case, the nRF is powered by a boost circuit (3V) so I need hardware to do the battery voltage measurement.
That just begs more questions. Why do you need to boost anything?
The nRF will operate from 1.8V to 3.6V on it's internal DC/DC.
If it's a gpio issue that forces you to run the nRF at 3v constant, then I suggest you take a close look at your peripheral IC's. Most devices have a wide operating range. As long as all the peripherals use the same VDD the comms voltages will all be the same.
It's because I'm using other external devices like buzzer etc...I'm also using some specific sensors which are not working below 3V.