Independent A/D Converter Supply And Reference Voltage; Battery Backup Domain; Table 24. Rtc_Af1 Pin - ST STM32F446 Series Reference Manual

RM0390
5.1.1

Independent A/D converter supply and reference voltage

To improve conversion accuracy, the ADC has an independent power supply which can be
separately filtered and shielded from noise on the PCB.
•
The ADC voltage supply input is available on a separate V
•
An isolated supply ground connection is provided on pin V
•
To ensure a better accuracy of low voltage inputs, the user can connect a separate
external reference voltage ADC input on V
to V
5.1.2

Battery backup domain

Backup domain description
To retain the content of the RTC backup registers, backup SRAM, and supply the RTC when
V is turned off, V
DD
battery or by another source.
To allow the RTC to operate even when the main digital supply (V
pin powers the following blocks:
•
The RTC
•
The LSE oscillator
•
The backup SRAM when the low-power backup regulator is enabled
•
PC13 to PC15 I/Os
The switch to the V
block.
Warning:
If no external battery is used in the application, it is recommended to connect the V
V with a 100 nF external decoupling ceramic capacitor in parallel.
DD
When the backup domain is supplied by V
following functions are available:
•
PC14 and PC15 can be used as either GPIO or LSE pins
•
PC13 can be used as a GPIOas the RTC_AF1 pin (refer to
more details about this pin configuration)
.
DDA
pin can be connected to an optional standby voltage supplied by a
BAT
supply is controlled by the power-down reset embedded in the Reset
BAT
During
t
RSTTEMPO
is detected, the power switch between V
connected to V
During the startup phase, if V
t
RSTTEMPO
and V > V
DD
through an internal diode connected between V
power switch (V
If the power supply/battery connected to the V
support this current injection, it is strongly recommended to
connect an external low-drop diode between this power
supply and the V
. The voltage on V
REF
(temporization at V
.
BAT
DD
(refer to the datasheet for the value of t
+ 0.6 V, a current may be injected into V
BAT
).
BAT
pin.
BAT
(analog switch connected to V
DD
RM0390 Rev 4
Power controller (PWR)
pin.
DDA
.
SSA
ranges from 1.8 V
REF
) is turned off, the V
DD
startup) or after a PDR
DD
and V
BAT DD
is established in less than
RSTTEMPO
and the
DD
pin cannot
BAT
Table 24: RTC_AF1 pin
BAT
remains
)
BAT
pin to
BAT
), the
DD
for
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