STM32F769AI datasheet(36/255 Pages) STMICROELECTRONICS

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Functional overview

STM32F765xx STM32F767xx STM32F768Ax STM32F769xx

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DocID029041 Rev 4

The RTC clock sources can be:

•

A 32.768 kHz external crystal (LSE)

•

An external resonator or oscillator(LSE)

•

The internal low power RC oscillator (LSI, with typical frequency of 32 kHz)

•

The high-speed external clock (HSE) divided by 32

The RTC is functional in VBAT mode and in all low-power modes when it is clocked by the

LSE. When clocked by the LSI, the RTC is not functional in VBAT mode, but is functional in

all low-power modes.

All RTC events (Alarm, WakeUp Timer, Timestamp or Tamper) can generate an interrupt

and wakeup the device from the low-power modes.

2.21

Low-power modes

The devices support 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 be put either in main regulator mode (MR) or in low-power

mode (LPR). Both modes can be configured as follows (see Table 5: Voltage regulator

modes in stop mode):

–

Normal mode (default mode when MR or LPR is enabled)

–

Under-drive 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 and

LPTIM1 asynchronous interrupt).

•

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

Table 5. Voltage regulator modes in stop mode

Voltage regulator

configuration

Main regulator (MR)

Low-power regulator (LPR)

Normal mode

MR ON

LPR ON

Under-drive mode

MR in under-drive mode

LPR in under-drive mode

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