S-8426AAA-J8T1X Datasheet, PDF (10/37 Pages) Seiko Instruments Inc – BATTERY BACKUP SWITCHING IC

BATTERY BACKUP SWITCHING IC
S-8426A Series
Rev.2.0_02
2. 2 PREEND Voltage Detector
The PREEND voltage detector monitors input voltage (VBAT) (VBAT pin voltage). The detection voltage can
be selected in the range of 1.7 to 3.4 V in 0.1 V step. By using this function, IC notifies if the backup battery is
scarce. The result of detection is output at the PREEND pin: “Low” for lower voltages than the detection
level and “High” for higher voltages than the release level.
2. 3 RESET Voltage Detector
The RESET voltage detector monitors output voltage (V_OUT) (VOUT pin voltage). The detection voltage can
be selected in the range of 1.7 to 3.4 V in 0.1 V step. The result of detection is output at the RESET pin:
“Low” for lower voltages than the detection level and “High” for higher voltages than the release level. RESET
outputs the normal logic if the VOUT pin voltage is 1.0 V or more.
Caution
The PREEND and RESET voltage detectors use the different pins, respectively.
Practically, the current is taken from the VBAT side, and consider the I/O voltage
difference (V_dif) of M1 when M1 is ON.
3. Switch Unit
The switch unit consists of the VSW1 and VSW2 detectors, a switch controller, voltage regulator 2, and switch
transistor M1 (Refer to Figure 14).
VOUT
VIN
REG2
M1
VBAT
Switch
controller
V_SW1
detector
V_SW2
detector
Figure 14
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