Independent A/D And D/A Converter Supply And Reference Voltage; Battery Backup Domain - STMicroelectronics RM0365 Reference Manual

RM0365
V
DD
•
VDD18 = 1.65 to 1.95 V (VDD18 domain): power supply for digital core, SRAM and
Flash memory.
VDD18 is internally generated through an internal voltage regulator .
• V
DDA
operational amplifiers, temperature sensor, PLL, HSI 8 MHz oscillator, LSI 40 kHz
oscillator, and reset block.
V
DDA
It is forbidden to have V
between V
•
V
BAT
backup registers when V
power switch switches the backup power to V
connected to V
8.1.1

Independent A/D and D/A converter supply and reference voltage

To improve conversion accuracy, the ADC and the DAC have an independent power supply
which can be separately filtered and shielded from noise on the PCB.
The ADC and DAC voltage supply input is available on a separate VDDA pin. An isolated
supply ground connection is provided on the VSSA pin.
144- and 100-pin package connections (only on STM32F302xB/CD/E)
To ensure a better accuracy on low-voltage inputs and outputs, a separate external
reference voltage can be connected on VREF+. VREF+ is the highest voltage, represented
by the full scale value, for an analog input (ADC) or output (DAC) signal.
64-pin, 49-pin, 48-pin and 32-pin package connections
On these packages, the VREF+ and VREF- pins are not available. They are internally
connected to the ADC voltage supply (V
The V
DDA
supply is used, V
circuit in order to ensure a noise free V
When V
DDA
a safe potential difference between V
external Schottky diode can be used between V
maximum allowed difference.
8.1.2

Battery backup domain

To retain the content of the Backup registers and supply the RTC function when V
turned off, V
or by another source.
The V
BAT
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.
must always be kept lower than or equal to V
, V = 2.0 to 3.6 V : external power supply for ADC, DAC, comparators,
SSA
must be in the 2.4 to 3.6 V range when the OPAMP and DAC are used.
DDA
and V to guarantee that this condition is met.
DD DDA
= 1.65 to 3.6 V: Backup power supply for RTC, LSE oscillator, PC13 to PC15 and
DD
.
DD
supply/reference voltage can be equal to or higher than V
can be externally connected to V
DDA
is different from V
DD
pin can be connected to an optional standby voltage supplied by a battery
BAT
pin powers the RTC unit, the LSE oscillator and the PC13 to PC15 I/Os, allowing
DocID025202 Rev 7
< V - 0.4 V. An external Schottky diode must be placed
DD
is not present. When V
. If V
DD
) and ground (V
DDA
/reference voltage.
DDA
, V must always be higher or equal to V
DDA
and V during power-up/power-down, an
DDA DD
and V
DD
Power control (PWR)
.
DDA
supply is present, the internal
DD
is not used, it must be
BAT
) respectively.
SSA
. When a single
DD
, through the external filtering
DD
DD
. Refer to the datasheet for the
DDA
. To maintain
is
DD
BAT
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