ST ST32M103 Series - Power Control (PWR); Power Supplies; Independent A;D Converter Supply and Reference Voltage; Figure 3. Power Supply Overview

UM0306 Power control (PWR)
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3 Power control (PWR)
3.1 Power supplies
The device requires a 2.0-3.6V operating voltage supply (V
DD
). An embedded regulator is
used to supply the internal 1.8V digital power.
The Real-Time Clock (RTC) and backup registers can be powered from the V
BAT
voltage
when the main V
DD
supply is powered off.
Figure 3. Power supply overview
3.1.1 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
DDA
pin.
● An isolated supply ground connection is provided on pin V
SSA
.
When available (according to package), V
REF-
must be tied to V
SSA
.
On 100-pin packages:
To ensure a better accuracy on low voltage inputs, the user can connect a separate external
reference voltage ADC input on V
REF+
and V
REF-
. The voltage on V
REF+
can range from 0V
to V
DDA
.
On packages with 64 pins or less:
The ADC voltage supply and ground are internally tied to the ADC reference voltage pins.
A/D converter
V
DDA
V
DD
V
SSA
(3.3V)
V
REF+
V
BAT
V
SS
I/O Ring
(from 0V
(V
DD
)
(V
DD
)
up to V
DDA
)
BKP registers
Temp. sensor
Reset block
STANDBY circuitry
PLL
(Wake-up logic,
IWDG)
RTC
Voltage Regulator
Core
Memories
digital
peripherals
Low voltage detector
V
REF-
V
DDA
domain
V
DD
domain
1.8V domain
Backup domain
LSE crystal 32K osc
RCC BDCR register
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