Numerous low power modes

AN3193

6/13

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Numerous low power modes

At a higher architectural level, the power consumption of the STM32L1 can be modulated by

entering one of seven low power modes. The power consumption can be reduced by

progressively disabling the frequency-independent current sources (the clock sources, the

non-volatile memory and the regulator) up to the point where most of the chip is powered

down. The following table summarizes the features available for each mode and provides

an indication of the current consumption.

Table 1. STM32L1xx low power mode overview

Two new modes have been implemented on the STM32L1xx in addition to the STM32F

modes: the Low power run and Low power sleep modes. They offer Run and Sleep mode

functionality for applications with extremely low current consumption where some

peripherals cannot be switched off (for instance communication peripherals or timers), or

where the CPU is processing continuously at low speed to minimize current variations.

Several functional blocks can be used to reach a very low current:



The voltage regulator is in low power (LP) mode to reduce its quiescent current



Non-volatile memory can be switched off, processing being done on the 16-Kbyte RAM



The master clock source comes from the MSI internal RC oscillator, which can be

reduced down to 1.5 µA.

The maximum current that the regulator can deliver in LP mode only limits the operating

frequency and the number of peripherals that can be activated.

Low power

mode

Consumption

CPU

Flash

/ EEPROM

RAM

DMA &

Periph.

Clock

LCD RTC

Sleep

100 µA/MHz (Range 1)

No

ON

ON

Active

Any

Available

82 µA / MHz (Range 2)

65 µA/MHz (Range 3)

Low power

run

10.4 µA

(Flash OFF, 32 kHz)

Yes ON or OFF

ON

Active

MSI

Available

Low power

sleep

5.1 µA

(periph. OFF)

No

OFF

ON

Active

MSI

Available

6.1 µA

(1 timer ON)

Stop

with RTC

1.3 µA (1.8 V)

No

OFF

ON

Frozen

LSE,

LSI

Available

1.6 µA (3 V)

Stop

500 nA

No

OFF

ON

Frozen

LSE,

LSI

OFF OFF

Standby

with RTC

1.3 µA (3 V)

OFF

OFF

OFF

OFF

LSE,

LSI

OFF

ON

1 µA (1.8 V)

Standby

270 nA

OFF

OFF

OFF

OFF

LSE,

LSI

OFF OFF