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10 POWER CONTROL CIRCUIT FOR BATTERY BACKUP FUNCTION
S5U1C17801T1100 HARDWARE MANUAL
EPSON
29
(SOFTWARE EVALUATION TOOL FOR S1C17801)
10 Power Control Circuit for Battery
Backup Function
SVT17801 has a battery backup function, and is equipped with a power control circuit allowing for this function.
Battery Backup Function
Three power supply lines are available on the S1C17801, i.e., VDD, AVDD and RTCVDD. VDD covers CPU core, log-
ic circuits, and I/O interface circuits, AV
DD covers analog circuits (ADC), and RTCVDD covers RTC and IVRAM.
The battery backup function supplies power only to RTCV
DD while stopping the power to AVDD and VDD. This
means that the function stops all operations except operating RTC and retaining contents inside IVRAM with low
power consumption. Because the power is supplied only to the minimum indispensable functions, leak current can
also be reduced drastically compared with sleep mode.
AVDD
VDD
RTCVDD
S1C17801
The SVT17801 is designed to connect the coin battery (CR2032) with RTCVDD, enabling RTC to keep functioning
and IRAM to retain its contents even if power supply from AC/DC adapter should be stopped.
In normal status, the power is supplied from AC/DC adapter without using the battery.
Power Control Circuit for Battery Backup Function
Figure 10.2.1 shows the power control circuit for SVT17801 battery backup function.
VDD, AVDD
POWER SW
RESET SW
#RESET
WAKEUP GPIO(P43)
GPIO(PC2) #STBY
S1C17801
RT
C
RTCVDD
IVRAM
5V
3.3VEN
(WAKEUP: Active HIGH signal)
Power switch
Active HIGH
Regulator
Fig. 10.2.1 Power Control Circuit for Battery Backup Function