s-8424a Seiko Instruments Inc., s-8424a Datasheet - Page 19

• Manufacturer Part Number: s-8424a
• Description: Battery Backup Switching Ic
• Manufacturer: Seiko Instruments Inc.

Rev.2.2
3. Switch Unit
2.2 PREEND Voltage Detector
2.3 RESET Voltage Detector
The switch unit consists of the V
transistor M1 (Refer to “ Figure 8 Switch Unit”).
3.1 V
_00
The PREEND voltage detector monitors the input voltage V
can be selected from between 1.7 V and 3.4 V in 0.1 V steps. A higher voltage can also be seclected
keeping a constant difference with the RESET voltage. This function enables the warning that the backup
battery is running out. The detection result is output to the PREEND pin: “Low” for lower voltages than
the detection voltage and “High” for higher voltages than the release voltage. The power supply of the
supplied from the VIN pin to the VOUT pin (V
supplied from the VBAT pin to the VOUT pin (V
The RESET voltage detector monitors the output voltage V
voltage can be selected from between 1.7 V and 3.4 V in 0.1 V steps. 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 V OUT pin voltage is 1.0 V or more.
Caution The PREEND and RESET voltage detectors use the different pins, respectively.
The V
controller. The detection voltage (V
+ V
PREEND voltage detector is supplied from the VIN pin. The output is valid only when the voltage is
SW1
DET1
Detector
SW1
.
Practically, the current is taken from the VBAT side, and consider the I/O voltage
difference (V
detector monitors the power supply voltage V
dif
VIN
) of M1 when M1 is ON.
SW1
Seiko Instruments Inc.
and V
SW1
controller
REG2
Switch
SW2
Figure 8 Switch Unit
) can be set to 77 ± 2% or 85 ± 2% of the CS release voltage
detectors, a switch controller, voltage regulator 2, and switch
VOUT
IN
IN
≥ V
< V
SW1
SW1
detector
M1
V
IN
). The output is the low level when the voltage is
SW1
).
and sends the results of detection to the switch
OUT
BAT
BATTERY BACKUP SWITCHING IC
(VOUT pin voltage). The detection
(VBAT pin voltage). The detection voltage
VBAT
detector
V
SW2
S-8424A Series
19