Power control (PWR) RM0008
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When the backup domain is supplied by V
DD
(analog switch connected to V
DD
), the
following functions are available:
● PC14 and PC15 can be used as either GPIO or LSE pins
● PC13 can be used as GPIO, TAMPER pin, RTC Calibration Clock, RTC Alarm or
second output (refer to Section 5: Backup registers (BKP) on page 61)
Note: Due to the fact that the switch only sinks a limited amount of current (3 mA), the use of
GPIOs PC13 to PC15 is restricted: only one I/O at a time can be used as an output, the
speed has to be limited to 2 MHz with a maximum load of 30 pF and these IOs must not be
used as a current source (e.g. to drive an LED).
When the backup domain is supplied by V
BAT
(analog switch connected to V
BAT
because
V
DD
is not present), the following functions are available:
● PC14 and PC15 can be used as LSE pins only
● PC13 can be used as TAMPER pin, RTC Alarm or Second output (refer to section
Section 5.4.2: RTC clock calibration register (BKP_RTCCR) on page 63).
4.1.3 Voltage regulator
The voltage regulator is always enabled after Reset. It works in three different modes
depending on the application modes.
● In Run mode, the regulator supplies full power to the 1.8 V domain (core, memories
and digital peripherals).
● In Stop mode the regulator supplies low-power to the 1.8 V domain, preserving
contents of registers and SRAM
● In Standby Mode, the regulator is powered off. The contents of the registers and SRAM
are lost except for the Standby circuitry and the Backup Domain.
4.2 Power supply supervisor
4.2.1 Power on reset (POR)/power down reset (PDR)
The device has an integrated POR/PDR circuitry that allows proper operation starting
from/down to 2 V.
The device remains in Reset mode when V
DD
/V
DDA
is below a specified threshold,
V
POR/PDR
, without the need for an external reset circuit. For more details concerning the
power on/power down reset threshold, refer to the electrical characteristics of the datasheet.
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