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HOW TO MINIMIZE THE ST7 POWER CONSUMPTION

7.2.1 Measurement Configuration

– The port PA0 (through which external interrupt is applied to MCU) is configured as pull up

interrupt.

– The sensitivity of the interrupt is configured as rising edge.

– Then the capacitor is charged and immediately the MCU is put into the corresponding mode

(Wait, Slow-Wait, Halt) by calling “WFI” or “HALT” instruction and setting some bits.

– As soon as the capacitor charges to 0.7Vdd, the MCU takes it as external interrupt and

comes out of that mode.

– The capacitor is then discharged by setting PA0 port to Push-Pull Output at low level and

small delay is then provided to let the capacitor discharge fully before charging it next time.

– The MCU is again put into corresponding mode and the same process is repeated. The

Measurement of current consumption is done in continuous interrupted mode.

– In Option Byte, PLL is disabled, Internal RC Oscillator is OFF, LVD is Off & No Reset when

Halt is selected.

Figure 5. Hardware Setup

7.2.2 Consumption

The consumption mainly depends on the Wake-Up frequency of the MCU from different

is fixed but the internal pull up resistance value varies depending upon the voltage supply of

7.2.2.1 Wait Mode

Methodology: An external CLK source, up to 16MHz is used on pin CLKIN. PLL is disabled

e

i0

PA0

mA

ST7LITE0