Low-Power Modes - ST STM32L15 QC Series Datasheet

Functional overview
3.1

Low-power modes

The ultra-low-power STM32L151xC/C-A and STM32L152xC/C-A devices support dynamic
voltage scaling to optimize its power consumption in run mode. The voltage from the internal
low-drop regulator that supplies the logic can be adjusted according to the system's
maximum operating frequency and the external voltage supply.
There are three power consumption ranges:
•
Range 1 (V
•
Range 2 (full V
•
Range 3 (full V
only with the multispeed internal RC oscillator clock source)
Seven low-power modes are provided to achieve the best compromise between low-power
consumption, short startup time and available wakeup sources:
•
Sleep mode
In Sleep mode, only the CPU is stopped. All peripherals continue to operate and can
wake up the CPU when an interrupt/event occurs. Sleep mode power consumption at
16 MHz is about 1 mA with all peripherals off.
•
Low-power run mode
This mode is achieved with the multispeed internal (MSI) RC oscillator set to the MSI
range 0 or MSI range 1 clock range (maximum 131 kHz), execution from SRAM or
Flash memory, and internal regulator in low-power mode to minimize the regulator's
operating current. In low-power run mode, the clock frequency and the number of
enabled peripherals are both limited.
•
Low-power sleep mode
This mode is achieved by entering Sleep mode with the internal voltage regulator in
Low-power mode to minimize the regulator's operating current. In Low-power sleep
mode, both the clock frequency and the number of enabled peripherals are limited; a
typical example would be to have a timer running at 32 kHz.
When wakeup is triggered by an event or an interrupt, the system reverts to the run
mode with the regulator on.
•
Stop mode with RTC
Stop mode achieves the lowest power consumption while retaining the RAM and
register contents and real time clock. All clocks in the V
PLL, MSI RC, HSI RC and HSE crystal oscillators are disabled. The LSE or LSI is still
running. The voltage regulator is in the low-power mode.
The device can be woken up from Stop mode by any of the EXTI line, in 8 µs. The EXTI
line source can be one of the 16 external lines. It can be the PVD output, the
Comparator 1 event or Comparator 2 event (if internal reference voltage is on), it can
be the RTC alarm(s), the USB wakeup, the RTC tamper events, the RTC timestamp
event or the RTC wakeup.
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range limited to 1.71 V - 3.6 V), with the CPU running at up to 32 MHz
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range), with a maximum CPU frequency of 16 MHz
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range), with a maximum CPU frequency limited to 4 MHz (generated
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DS10262 Rev 8
STM32L151xC/C-A STM32L152xC/C-A
domain are stopped, the
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