GD32VF103 User Manual
51
Generally, digital circuits are powered by V
DD
, while most of analog circuits are powered by
V
DDA
. To improve the ADC and DAC conversion accuracy, the independent power supply V
DDA
is implemented to achieve better performance of analog circuits. V
DDA
can be externally
connected to V
DD
through the external filtering circuit that avoids noise on V
DDA
, and V
SSA
should be connected to V
SS
through the specific circuit independently. Otherwise, if V
DDA
is
different from V
DD
, V
DDA
must always be higher, but the voltage difference should not exceed
0.2V.
To ensure a high accuracy on low voltage ADC and DAC, the separate external reference
voltage on V
REF
should be connected to ADC/DAC pins. According to the different packages,
V
REF+
pin must be connected to V
DDA
pin, V
REF-
pin must be connected to V
SSA
pin. The V
REF+
pin is only available on no less than 100-pin packages, or else the V
REF+
pin is not available
and internally connected to V
DDA.
The V
REF-
pin is only available on no less than 100-pin
packages, or else the V
REF-
pin is not available and internally connected to V
SSA
.
3.3.3.
1.2V power domain
The main functions that include RISC-V logic, AHB/APB peripherals, the APB interfaces for
the Backup domain and the V
DD
/V
DDA
domain, etc, are located in this power domain. Once the
1.2V is powered up, the POR will generate a reset sequence on the 1.2V power domain. If
need to enter the expected power saving mode, the associated control bits must be
configured. Then, once a WFI (Wait for Interrupt) or WFE (Wait for Event) instruction is
executed, the device will enter an expected power saving mode which will be discussed in
the following section.
3.3.4.
Power saving modes
After a system reset or a power reset, the GD32VF103 MCU operates at full function and all
power domains are active. Users can achieve lower power consumption through slowing
down the system clocks (HCLK, PCLK1, PCLK2) or gating the clocks of the unused
peripherals. Besides, three power saving modes are provided to achieve even lower power
consumption, they are Sleep mode, Deep-sleep mode, and Standby mode.
Sleep mode
The Sleep mode is corresponding to the SLEEPING mode of the RISC-V. In Sleep mode,
only clock of RISC-V is off. To enter the Sleep mode, it is only necessary to clear the
CSR_SLEEPVALUE bit in the RISC-V System Control Register, and execute a WFI or WFE
instruction. If the Sleep mode is entered by executing a WFI instruction, any interrupt can
wake up the system. If it is entered by executing a WFE instruction, any wakeup event can
wake up the system. The mode offers the lowest wakeup time as no time is wasted in interrupt
entry or exit.