GD32F20x User Manual
64
Figure 3-1. Power supply overview
PMU
CTL
FWDGT
IRC40K
LDO
LXTAL
RTC
WKUPF
IRC8M
HXTAL
PLLs
POR/PDR
BPOR
ADC
Backup Domain
NRST
PA0
V
DD
Domain
WKUP
WKUPR
V
DD
V
BAT
Power Switch
3.3V
V
BAK
Cortex-M3
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
WKUPN
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 then the V
BAK
pin drives Backup Domain. The Backup domain
provides power to RTC unit, LXTAL oscillator, BPOR and BREG, and three pads, including
PC13 to PC15. In order to ensure the content of the registers in Backup domain and the RTC
work normally, 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 includes 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 Corte
x™-M3 needs to setup the RTC
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...