How to: power optimization techniques for measuring 3V coin cell battery level

[Tomi]

We have IoT gadget, where we use coin cell (CR2032) as power supply. Now, we would like to connect U_bat directly to ADC to measure battery level every n minutes, but keep ADC disabled between the intervals. Since we are very concerned about the power consumption, my question is:

What is amount of current going into ADC pin, when ADC is disabled?

[Stefan Birnir Sverrisson]

Hi Tomi

Im not sure what IC you are using, nRF51 or nRF52, but there are low power examples for both on Nordic's Github page, nRF51 ADC, nRF52 SAADC. These examples are for nRF5 SDK 11.

When ADC is disabled, no current is consumed.

For nRF51, when the ADC is enabled but not sampling, current consumption of the ADC is low, <1uA

For nRF52, when the SAADC is enabled but not sampling, current consumption of the SAADC is high, ~2mA. The current consumption is also ~2mA when the SAADC samples. The saadc_low_power example demonstrates how to disable the SAADC when not sampling, substantially decreasing the current consumption.

[sara]

Hello, The average current consumption of SAADC is higher than ADC, is it correct? If is, can we use ADC for nRF52? Thanks.