Using NRF51822 for full RTC and low power

[tuyenpham]

Hi all,

I need to using NRF51822 as a clock: second, min, hour, date.... I know I only use RTC as a timer 1s. When NRF51822 power off then time was lost. So, I must be use external a RTC chip? I concern it'll cost power consumption more because my system using battery. Any Nordic BLE MCU have full RTC with battery backup? thanks and regards,

[Roger Clark]

If you completely remove the power from the nRF51822 (or the nRF52) RTC and all other functions will stop.

Either you need an external RTC (which has its own battery),

Or.. you have a battery to power your nRF5 processor and put it into low power mode, when you are not using it for its main function.

[bjorn-spockeli]

If the product requires to accurately keep track of time over a long period of time then I recommend that you use an external Real-Time Clock and not the the Real-Time Counter(RTC) of the nRF51x22. If you put the nRF51x22 in System ON with 16kb RAM enabled and keep the RTC running then you should see about 2.6uA (SYSTEM-ON base current with 16 kB RAM enabled.) + 0.8uA (RC32k Run current)+ 0.1uA (RTC Run Current)= ~3.5uA.