Dear community,
I would like to keep the RTC value when I turn off my device (which use the Murata type ABZ based on STM32L072). I know the Vbat system is not available on STM32L0 but I neet to use this MCU. So I found the application note AN4718 which tell us how to design a Vbat system for STM32L0.
Following those guidelines, I managed to reproduce the "Case 1b: supply from main supply and battery or super capacitor backup wake up pin" by creating a software which goes to STOP mode when there is a voltage drop and wakes up from it when main supply is back.
My problem now is to choose the right components to be sure the super capacitor will keep the RTC for at least some days.
My main Supply is always 3.3V. In Active mode, my STM32L0 current consumption can be around 50mA and when I'm in STOP mode, the consumption drops under 1uA.
In the application note, there are references for the 2 schottky diodes and the PMOS but I don't know which resistor and super capacitor should I use to get the Vbackup works well ?
Thank you for your replies.
Regards.
