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AT32F413
Series Reference Manual
2022.06.27
Page 42
Rev 2.00
3.5 Power domain
1.2 V domain
1.2 V core domain includes a CPU core, SRAM, embedded digital peripherals and Phase Locked Loop
(PLL). Such power domain is supplied by LDO (voltage regulator).
VDD/VDDA domain
VDD/VDDA domain includes VDD domain and VDDA domain. The VDD domain contains I/O circuit,
power-saving mode wakeup circuit, watchdog timer, power-on reset/low voltage reset (POR/LVR), LDO
and all PAD circuits other than PC13, PC14 and PC15. The VDDA domain contains DAC/ADC (DA/AD
converters), temperature sensor and so on.
Typically, to ensure a better accuracy of ADC/DAC at a low voltage, the digital circuit is supplied by VDD
while the analog circuit is powered by VDDA. On 64-pin packages and packages with less pins, the
external reference voltage VREF+ and VREF- are connected to the VDDA pin and VSSA pin, respectively.
Battery powered domain
The battery powered domain contains RTC circuit, LEXT oscillator, PC13, PC14 and PC15, which is
powered by either VDD or VBAT pin. When the VDD is cut off, the battery powered domain is
automatically switched to VBAT pin to ensure that RTC can work normally.
1)
When the battery powered domain is powered by VDD, the PC13 can be used as a general-purpose
I/O, tamper pin, RTC calibration clock, RTC alarm or second output, while the PC14 and PC15 can
be used as a GPIO or LEXT pin. (As an I/O port, PC13, PC14 and PC15 must be limited below 2
MHz, and to the maximum load of 30 pF, and these I/O ports must not be used as current sources)
2)
When the battery powered domain is powered by VBAT, the PC13 can be used as a a tamper pin,
RTC alarm or second output, while the PC14 and PC15 can only be used as a LEXT pin.
The switch of the battery powered domain will not be disconnected from VBAT because of the VDD
being at its rising phrase or due to VDD low voltage reset. If the power switch has not been switched to
the VDD when the VDD is powered on quickly, it is recommended to add a low votage drop diode
between VDD and VBAT in order to prevent the currents of VDD from being injected to VBAT. If there is
no external battery in the application, it is better to connet the VBAT to a 100 nF ceramic filter capacitor
that is externally connected to VDD.
3.6 Power saving modes
When the CPU does not need to be kept running, there are three types of low-power modes available
(Sleep mode, Deepsleep mode and Standby mode) to save power. Users can select the mode that gives
the best compromise according to the low-power consumption, short startup time, and available wakeup
sources. In addition, the power consumption in Run mode can be reduced by slowing down the system
clocks or gating the clocks on the APB and AHB peripherals when they are not used.
Sleep mode
The Sleep mode is entered by executing WFI or WFE command. There are two options to select the
Sleep mode entry mechanism through the SLEEPONEXIT bit in the Cortex ® -M4F system control
register.
SLEEP-NOW mode:
When SLEEPDEEP=0 and SLEEPONEXIT=0, the MCU enters Sleep mode as soon as WFI or WFE
instruction is executed.
SLEEP-ON-EXIT mode:
When SLEEPDEEP=0 and SLEEPONEXIT=1, the MCU enters Sleep mode as soon as the system exits
the lowest-priority interrupt service routine by executing the WFI instruction.
In Sleep mode, all clocks and LDO work normally except CPU clocks (stopped), and all I/O pins keep
the same state as in Run mode. The LDO provides an 1.2 V power (for CPU core, memory and
embedded peripherals) as it is in normal power consumption mode.
1)
If the WFI is executed to enter Sleep mode, any peripheral interrupt can wake up the device from
Sleep mode.
2)
If the WFE is executed to enter Sleep mode, the MCU exits Sleep mode as soon as an event occurs.