STM32L431 datasheet(25/200 Pages) STMICROELECTRONICS

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STM32L431xx

Functional overview

3.9.5

Reset mode

In order to improve the consumption under reset, the I/Os state under and after reset is

“analog state” (the I/O schmitt trigger is disable). In addition, the internal reset pull-up is

deactivated when the reset source is internal.

3.9.6

VBAT operation

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

supercapacitor, or from VDD when no external battery and an external supercapacitor are

present. The VBAT pin supplies the RTC with LSE and the backup registers. Three anti-

tamper detection pins are available in VBAT mode.

VBAT operation is automatically activated when VDD is not present.

An internal VBAT battery charging circuit is embedded and can be activated when VDD is

present.

Note:

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

do not exit it from VBAT operation.

CRC calculation

unit

OOO

GPIOs

OOO

(9)

pins

(10)

(11)

pins

(10)

1. Legend: Y = Yes (Enable). O = Optional (Disable by default. Can be enabled by software). - = Not available.

2. The Flash can be configured in power-down mode. By default, it is not in power-down mode.

3. The SRAM clock can be gated on or off.

4. SRAM2 content is preserved when the bit RRS is set in PWR_CR3 register.

5. Some peripherals with wakeup from Stop capability can request HSI16 to be enabled. In this case, HSI16 is woken up by

the peripheral, and only feeds the peripheral which requested it. HSI16 is automatically put off when the peripheral does not

need it anymore.

6. UART and LPUART reception is functional in Stop mode, and generates a wakeup interrupt on Start, address match or

received frame event.

7. I2C address detection is functional in Stop mode, and generates a wakeup interrupt in case of address match.

8. Voltage scaling Range 1 only.

9. I/Os can be configured with internal pull-up, pull-down or floating in Standby mode.

10. The I/Os with wakeup from Standby/Shutdown capability are: PA0, PC13, PE6, PA2, PC5.

11. I/Os can be configured with internal pull-up, pull-down or floating in Shutdown mode but the configuration is lost when

exiting the Shutdown mode.

Table 4. Functionalities depending on the working mode(1) (continued)

Peripheral

Run

Sleep

Low-

power

run

Low-

power

sleep

Stop 0/1

Stop 2

Standby Shutdown

VBAT

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