ST STM32G4 Series Reference Manual page 188

Power control (PWR)
ADC and DAC reference voltage
To ensure a better accuracy on low-voltage inputs and outputs, the user can connect to
V a separate reference voltage lower than V
REF+
represented by the full scale value, for an analog input (ADC) or output (DAC) signal.
V can be provided either by an external reference of by an internal buffered voltage
REF+
reference (VREFBUF).
The internal buffered voltage reference (VREFBUF) is enabled by setting the ENVR bit in
the Section 22.3.1: VREFBUF control and status register
buffered voltage reference (VREFBUF) is set to 2.048 V, 2.5 V or 2.9 V according the
VRS[1:0] bits setting. The internal buffered voltage reference can also provide the voltage to
external components through V
Voltage reference buffer (VREFBUF)
5.1.2 USB transceivers supply
The USB transceivers are supplied from V
from 3.0 V to 3.6 V.
5.1.3 Battery backup domain
To retain the content of the Backup registers and supply the RTC function when V
turned off, the VBAT pin can be connected to an optional backup voltage supplied by a
battery or by another source.
The VBAT pin powers the RTC unit, the LSE oscillator and the PC13 to PC15 I/Os, allowing
the RTC to operate even when the main power supply is turned off. The switch to the V
supply is controlled by the power-down reset embedded in the Reset block.
Warning:
If no external battery is used in the application, it is recommended to connect V
externally to V
When the backup domain is supplied by V
following pins are available:
•
PC13, PC14 and PC15, which can be used as GPIO pins
•
PC13, PC14 and PC15, which can be configured by RTC or LSE (refer to
188/2083
REF+
During
t
RSTTEMPO
has been detected, the power switch between V
remains connected to V
During the startup phase, if V
t (refer to the datasheet for the value of t
RSTTEMPO
and V > V
DD BAT
through an internal diode connected between V
power switch (V
If the power supply/battery connected to the VBAT pin cannot
support this current injection, it is strongly recommended to
connect an external low-drop diode between this power
supply and the VBAT pin.
with a 100 nF external ceramic decoupling capacitor.
DD
RM0440 Rev 1
. V
DDA REF+
(VREFBUF_CSR). The internal
pin. Refer to the device datasheet and to
for further information.
power supply pin. V
DD
(temporization at V
DD
.
BAT
is established in less than
DD
+ 0.6 V, a current may be injected into V
).
BAT
(analog switch connected to V
DD
is the highest voltage,
Section 22:
range for USB usage is
DD
DD
startup) or after a PDR
and V
BAT DD
RSTTEMPO
BAT
and the
DD
BAT
), the
DD
Section 34.3:
RM0440
is
BAT
)