I am currently involved in a project which we going to use ATSAM4E16E as the controlling mcu. We are currently in a doubt whether to use internal rtc or an external rtc. Reason for this doubt is that we expect our product to exist for about 5 years. If we use the internal rtc, the processor will be always on within it's lifetime. Because as this processor has no separate VBAT pins for rtc power we should keep the processor on at all the time (we can sleep it while not using other functions)
1. What do you recommend using? Internal rtc or an external rtc?
2. If internal rtc, please suggest a way to switch processor power source to a backup battery installed in the unit, when shut down. At this moment processor should go to sleep as it has been shut down