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AN4365

STM32F4 low-power application case

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3.3

Current consumption measurement

The average current consumption is the sum of the total energy consumed by the system in

Dynamic and Static power modes, divided by the average system loop time. The average

current is important because it provides a single value, which can be used to accurately

determine battery life or the total energy use of the system.

This application involves speed (maximum device frequency used for FFT), complexity

(sampling and transfer of 1024 samples) and STM32F4 low-power efficiency using the

Sleep and Standby modes associated with other low-power techniques (described in the

previous chapter).

3.3.1

Measuring current consumption

Figure 17. Application waveform overview

Master current consumption

Figure 18. Calculating Master average current consumption

Average Current (mA)~= (Run1_M*0,11 + Run2_M*0,08 + Sleep*49 + Run3_M*0,6 + StdBy*50,19)/100

Note:

The standby period on the Master side is controlled by the RTC which is driven by the LSI

RC oscillator. The LSI varies from 17 KHz to 47 KHz (refer to the STM32F4 datasheet). This

means that the period can be changed from one device to another, and this can slightly

impact the consumption.