STM32F3xx microcontroller low-power application example

AN4538

22/25

DocID026505 Rev 1

Figure 8. Log time display of the measured example

The time spent in each mode and the corresponding current consumption helps us to

calculate an estimated value of the whole application average current consumption. The

formula of the average current consumption is as follows:

Table 5 gives the time and the current consumption in different low-power modes of the

measured example. For Runx modes (x=1, 2, 3, 4, 5, 6), we assume that they are negligible

versus low-power modes in term of processing periods in a such low-power application.

Total time = wake up from Sleep3 mode time = 42488 ms

Note:

The current consumption of low-power modes is measured by holding the multimeter

display in each measured state of the application.

Applying the average formula gives:

I average = [(4.3 * 20015) + (2010 * 82) + (24.3 * 12957) + (2080 * 9336) + (2040 * 90)] /

42488 = 475 µA

So the calculation gives us a good average current consumption compared to the measured

one with almost only 1% error.

Table 5. low-power mode data of the measured example

Low-power modes

Active peripherals

Execution periods

(ms)

Average measured

current consumption

(µA)

Standby mode

RTC

(LSE, Backup domain)

20015

4.3

Sleep1 mode

RTC, USART1/DMA1

82

2010

Stop mode

RTC, USART1

12957

24.3

Sleep 2 mode

RTC, USART1/DMA1,

COMP2, TIM1

9336

2080

Sleep3 mode

RTC, USART1/DMA1

90

2040