STM32F217VG datasheet(24/173 Pages) STMICROELECTRONICS

24 / 173 page

Description

STM32F21xxx

24/173

Doc ID 17050 Rev 8

2.2.18

Low-power modes

The STM32F21x family supports three low-power modes 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.

●

Stop mode

The Stop mode achieves the lowest power consumption while retaining the contents of

SRAM and registers. All clocks in the 1.2 V domain are stopped, the PLL, the HSI RC

and the HSE crystal oscillators are disabled. The voltage regulator can also be put

either in normal or in low-power mode.

The device can be woken up from the Stop mode by any of the EXTI line. The EXTI line

source can be one of the 16 external lines, the PVD output, the RTC alarm / wakeup /

tamper / time stamp events, the USB OTG FS/HS wakeup or the Ethernet wakeup.

●

Standby mode

The Standby mode is used to achieve the lowest power consumption. The internal

voltage regulator is switched off so that the entire 1.2 V domain is powered off. The

PLL, the HSI RC and the HSE crystal oscillators are also switched off. After entering

Standby mode, the SRAM and register contents are lost except for registers in the

backup domain and the backup SRAM when selected.

The device exits the Standby mode when an external reset (NRST pin), an IWDG reset,

a rising edge on the WKUP pin, or an RTC alarm / wakeup / tamper /time stamp event

occurs.

Note:

The RTC, the IWDG, and the corresponding clock sources are not stopped when the device

enters the Stop or Standby mode.

2.2.19

VBAT operation

The VBAT pin allows to power the device VBAT domain from an external battery or an

external supercapacitor.

VBAT operation is activated when VDD is not present.

The VBAT pin supplies the RTC, the backup registers and the backup SRAM.

Note:

When the microcontroller is supplied from VBAT, external interrupts and RTC alarm/events

do not exit it from VBAT operation.

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