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GD32F403xx User Manual
62
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
0.3V.
To ensure a high accuracy on ADC and DAC, the ADC / DAC independent external reference
voltage should be connected to V
REF+
/ V
REF-
pins. According to the different packages, V
REF+
pin can be connected to V
DDA
pin, or external reference voltage which refers to
Table 13-1. DAC I/O description
, 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
1.2V power domain supplies power for Cortex
®
-M4 logic, AHB/APB peripherals, the APB
interfaces for the Backup domain and the V
DD
/ V
DDA
domain, etc. 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.
High-driver mode
If the 1.2V power domain runs with high frequency and opens many functions, it is
recommended to enter high-driver mode. The following steps are needed when using high-
driver mode.
◼
IRC8M or HXTAL selected as system clock.
◼
Set HDEN bit in PMU_CTL register to 1 to open high-driver mode.
◼
Wait HDRF bit be set to 1 in PMU_CS register.
◼
Set HDS bit in PMU_CTL register to 1 to switch LDO to high-driver mode.
◼
Wait HDSRF bit be set to 1 in PMU_CS register. And enter high-driver mode.
◼
Running the application at high frequency.
The high-driver mode exit by resetting HDEN and HDS bits in PMU_CTL register after IRC8M
or HXTAL selected as system clock. The high-driver mode exit automaticly when exiting from
Deep-sleep mode.
3.3.4.
Power saving modes
After a system reset or a power reset, the GD32F403xx MCU operates at full function and all