AT32WB415
Series Reference Manual
2022.04.13
Page 43
Ver 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). It can be configured as power-on,
low-power or power-off in three power saving modes.
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 (WDT), power-on reset/low voltage reset (POR/LVR),
LDO, ERTC circuit, LEXT oscillator and and all PAD circuits except PC13, PC14 and PC15. The VDDA
domain contains a ADC (AD converter), temperature sensor and so on.
Typically, to ensure a better accuracy of ADC at a low voltage, the digital circuit is supplied by VDD while
the analog circuit is powered by VDDA. he external reference voltage VREF+ and VREF- are connected
to the VDDA pin and VSSA pin, respectively.
Battery powered domain
The battery powered domain contains ERTC 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, ERTC calibration clock, ERTC 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 V
BAT
, the PC13 can be used as a a tamper pin,
ERTC 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 V
BAT
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 V
BAT
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 to the APB and AHB peripherals when they are not used.
Sleep mode
The Sleep mode is entered by executing WFI or WFE instruction. There are two options to select the
Sleep mode entry mechanism through the SLEEPONEXIT bit in the Cortex ® -M4 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.
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. The LDO output voltage is
configurable by the PWC_LDOOV register.
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.