What is the capacity of battery that can be used to power STM32H7 ?

[Kavana shree]

I want use battery to STM32H7 as a backup supply. The requirement scenario is before I power STM32H7 ​via USB, and before USB is enumerated, I want to use the backup supply from battery for 2mins. 4 LEDS and switches will be in use. What is the power consumption of STM32H7 at that point of time? What capacity of battery I should use? At what rate should I charge the battery? Also should I use separate battery for RTC? At what frequency MCU will be working at that point of time when MCU frequency of operation is 300MHZ later.

[T J]

Rough figures :( sorry for that, but its your work, this is a starting point.

Firstly, the RTC is not likely to be accurate over any period of time,

So, not sure if you really want to use it.

Secondly, a Processor will draw varying power depending on the PCB systems.

SDRAM for example will more than double the power requirement.

the 18650 is the highest volume battery shape, so you should use that.

If you go with a lithium Ion type, you would enjoy approx 2500mAH @3.4V

the recommended chargeing time is 10 hours, ie 250mA charge.

without SDRAM at 300MHz I am guessing approx 50-100mA draw, thats 50-25hours from that fully charged battery.

RTC batteries are very low current, unable to produce more than a few mAs.

I use a coin cell and a true RTC DS3232. this offers worst case 2Minutes error per year. however, if you remain close to 25C the accuracy is much better than that.