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Question asked by s.esat on Jan 31, 2013
Latest reply on Feb 1, 2013 by s.esat
Hi everyone
I hope someone could confirm this:
I am designing a project with  STM32F407vg that must operate from battery  for about 2 years in STANDBY MODE,
In my system i have 2 batteries , external 12v that is regulated to 3.3v VDD  ( using regulator )  for mcu but this regulator is turned off while the MCU  in standby mode to save energy (there are other ICs to switch them off),   and I have 3.6V battery ( about 600mA) on the PCB .
The datasheet declares that the stanbymode  current for the mcu is about 4uA if RTC is ON, so
600mAh  will keep the mcu in stanby mode for about 17 years (2 years is enough) !! that is ok .. is that right?
Now I have problem in the connections so please confirm if that right or not.
The output of the regulator is feeded to the VDD of the mcu and the 3.6battery is feeded by an diod to vdd to the mcu , is that ok?
when a wake up ocurres by PA0 rising edge  or RTC alarm output  the MCU will  turn to the normal mode and enable the external regulator to operate from the external 12v battery ..Is my configuration ok?
should I connect the VBAT  pin  of the mcu to vdd or to the 3.6 battery ( before diod or after diod)?
Thank you in advanced