I have developed a board based on i.MX6 Dual Lite and PMIC MMPF0100.
I need RTC function.
My system hasn't a main battery but is supplied by a wall mount power supply. I need that RTC will keep the time when the main power supply will be disconnected for a little.
So, I have provided a supercap but it seems that it isn't enough.
Now I'm revising my board and I would provide a small lithium rechargable battery.
But, I have some doubts.
1) How is the voltage required to mantain RTC time when the main power is OFF? In the i.MX6 datasheet I read that "Backup battery supply range (VDD_SNVS_IN) is minimum 2.9V and maximum 3.3V". Is it correct?
2) I read that the Maximum supply current of VDD_SNVS_IN is 275uA
With the supply current specified (275uA), the small coin lithium batteries (like ML614 or ML621) has a voltage drop and doesn't assure that the voltage will be above 2.9V, even if it is full charged.
Should I provide a bigger battery or there is something that I miss?
Onto the SABRE SDP is present a ML414 that for sure can't assure a voltage above 2.9V with a current sink of 275uA.
Thanks very much,