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.

[Roger Clark]

Sorry. I should have made it clear I was referring to using a 32khz crystal rather than the 32kHz RC oscillator

For very accurate time keeping even that would not be enough as I think you require temperature compensation.

It probably depends on how accurate and over what time period and under what conditions you need to keep accurate time.

Ultimately if you want to be very accurate, you should probably use a external GPS for your timekeeping.