Independent A/D Converter Supply And Reference Voltage; Battery Backup Domain - ST STM32F207 Series Reference Manual

RM0033
4.1.1

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
4.1.2

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, plus PI8 I/O (when available)
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
. The voltage on V
REF
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 (temporization at V
t
RSTTEMPO
is detected, the power switch between V
connected to V .
BAT
During the startup phase, if V
t (Refer to the datasheet for the value of t
RSTTEMPO
and V > V + 0.6 V, a current may be injected into V
DD BAT
through an internal diode connected between V
power switch (V ).
BAT
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
BAT
RM0033 Rev 9
SSA
ranges from 1.8 V to V
REF
startup) or after a PDR
DD
BAT
is established in less than
DD
pin.
Power control (PWR)
pin.
DDA
.
DDA
) is turned off, the V
DD
and V remains
DD
)
RSTTEMPO
BAT
and the
DD
pin cannot
BAT
BAT
65/1381
.
BAT
pin to
83