GD32VF103 User Manual
48
Figure 3-1. Power supply overview
PMU
CTL
FWDGT
IRC40K
LDO
LXTAL
RTC
WKUP3
IRC8M
HXTAL
PLLs
POR/PDR
BPOR
ADC
Backup Domain
NRST
PA0
V
DD
Domain
WKUP1
WKUP4
V
DD
V
BAT
Power Switch
3.3V
V
BAK
RISC-V
AHB IPs
1.2V Domain
APB IPs
SLEEPING
SLEEPDEEP
1.2V
LVD: Low Voltage Detector
LDO: Voltage Regulator
POR: Power On Reset
PDR: Power Down Reset
BPOR: V
BAK
Power On Reset
WKUP2
LVD
DAC
V
DDA
3.3V
V
DDA
Domain
BREG
BREG: Backup registers
3.3.1.
Battery backup domain
The Backup domain is powered by the V
DD
or the battery power source (V
BAT
) selected by the
internal power switch, and the V
BAK
pin which drives Backup Domain, supplies power for RTC
unit, LXTAL oscillator, BPOR and BREG
,
and three pads, including PC13 to PC15. In order
to ensure the content of the Backup domain registers and the RTC supply, when V
DD
supply
is shut down, V
BAT
pin can be connected to an optional standby voltage supplied by a battery
or by another source. The power switch is controlled by the Power Down Reset circuit in the
V
DD
/V
DDA
domain. If no external battery is used in the application, it is recommended to
connect V
BAT
pin externally to V
DD
pin with a 100nF external ceramic decoupling capacitor.
The Backup domain reset sources include the Backup domain power-on-reset (BPOR) and
the Backup Domain software reset. The BPOR signal forces the device to stay in the reset
mode until V
BAK
is completely powered up. Also the application software can trigger the
Backup domain software reset by setting the BKPRST bit in the RCU_BDCTL register to reset
the Backup domain.
The clock source of the Real Time Clock (RTC) circuit can be derived from the Internal 40KHz
RC oscillator (IRC40K) or the Low Speed Crystal oscillator (LXTAL), or HXTAL clock divided
by 128. When V
DD
is shut down, only LXTAL is valid for RTC. Before entering the power saving
mode by executing the WFI/WFE instruction, the RISC-V can setup the RTC register with an
expected wakeup time and enable the wakeup function to achieve the RTC timer wakeup