AN1014 datasheet(10/25 Pages) STMICROELECTRONICS

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HOW TO MINIMIZE THE ST7 POWER CONSUMPTION

Measurements:

Table 5. Consumption IDD (Slow-Wait Mode) at TA = + 25 °C

6.1.2.5 Active-Halt Mode

Methodology: A resonator oscillator is used with fosc at 4 / 8 MHz. PLL*2 is disabled. So, fosc2

is fosc/2. All peripherals are in reset configuration except the ports. All ports are set as Push-

Pull Outputs with low level. The MCCSR-OIE bit is set to 1 and the TB1 & TB0 of MCCSR bits

are set to 1. The MCC/RTC interrupt is used as the wake-up interrupt. The oscillator is ON, so

the total consumption also includes the oscillator consumption.

Measurements:

Table 6. Consumption IDD (Active-Halt Mode) at TA = + 25 °C

6.1.2.6 Halt Mode

Methodology: A resonator oscillator is used with Fosc at 4 / 8 MHz. PLL*2 is disabled. So,

Fosc2 is Fosc/2. All peripherals are in reset configuration except the ports. All ports are set as

Push-Pull Outputs with low level.

Measurements:

Table 7. Consumption IDD (Halt Mode) at TA = + 25 °C

6.1.3 Conclusion

Current consumption depends on VDD. Consumption increases with the increase of VDD and

fOSC. In Active-Halt mode, the time base for the MCC/RTC interrupt does not affect the current

consumption in this particular application. The oscillator is ON in Active-Halt mode, so the total

consumption also includes the oscillator consumption. In Halt mode, current consumption is

independent of VDD and fOSC.

fOSC(MHz)

fCPU(MHz)

IDD at VDD = 4.5 V

IDD at VDD = 5 V

IDD at VDD = 5.5 V

40.125

1.28 mA

1.44 mA

1.63 mA

4 / 8

0.25

1.59 mA

1.85 mA

2.10 mA

4 / 8

0.5

2.12 mA

2.45 mA

2.77 mA

4 / 8

2.69 mA

3.02 mA

3.39 mA

3.56 mA

3.99 mA

4.39 mA

fOSC(MHz)

IDD at VDD = 4.5 V

IDD at VDD = 5 V

IDD at VDD = 5.5 V

1.06 mA

1.20 mA

1.36 mA

1.19 mA

1.35 mA

1.53 mA

fOSC(MHz)

IDD at VDD = 4.5 V

IDD at VDD = 5 V

IDD at VDD = 5.5 V

0.1

µA0.1 µA0.1 µA

0.1

µA0.1 µA0.1 µA

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