I am considering using the RTC in the i.mx6 but have concerns about the battery life. It is my understanding that the lowest power consumption on the VDD_SNVS_IN is when the processor is in SLEEPDEEP mode (and then it is ~15uA). I also understand that to get the i.mx6 into this mode a control register has to be written to enable it. My concern is that if the power gets removed suddenly (AC power failure) that there will not be time to suddenly write this register and the i.mx6 will draw significantly larger currents from the battery and reduce the amount of time it can remain powered down before losing time.
I would like to know if anyone else has tried to use the internal RTC in a battery backed up configuration and how this worked.