Power control (PWR)
RM0365
99/1080
DocID025202 Rev 7
Warning:
During
t
RSTTEMPO
(temporization at V
DD
startup) or after a PDR
is detected, the power switch between V
BAT
and V
DD
remains
connected to V
BAT
.
During the startup phase, if V
DD
is established in less than
t
RSTTEMPO
(Refer to the datasheet for the value of t
RSTTEMPO
)
and V
DD
> V
BAT
+ 0.6 V, a current may be injected into V
BAT
through an internal diode connected between V
DD
and the
power switch (V
BAT
).
If the power supply/battery connected to the V
BAT
pin cannot
support this current injection, it is strongly recommended to
connect an external low-drop diode between this power
supply and the V
BAT
pin.
If no external battery is used in the application, it is recommended to connect V
BAT
externally to V
DD
with a 100 nF external ceramic decoupling capacitor (for more details refer
to AN4206).
When the RTC domain is supplied by V
DD
(analog switch connected to V
DD
), the following
functions are available:
•
PC13, PC14 and PC15 can be used as GPIO pins
•
PC13, PC14 and PC15 can be configured by RTC or LSE (refer to
functional description on page 724
Note:
Due to the fact that the switch only sinks a limited amount of current (3 mA), the use of
GPIOs PC13 to PC15 in output mode is restricted: the speed has to be limited to 2 MHz with
a maximum load of 30 pF and these I/Os must not be used as a current source (e.g. to drive
an LED).
When the RTC domain is supplied by V
BAT
(analog switch connected to V
BAT
because V
DD
is not present), the following functions are available:
•
PC13, PC14 and PC15 can be controlled only by RTC or LSE (refer to
RTC functional description on page 724
8.1.3 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 RTC Domain.