S-8425AAAFT-TB-X Datasheet, PDF (12/45 Pages) Seiko Instruments Inc – BATTERY BACKUP SWITCHING IC

BATTERY BACKUP SWITCHING IC
S-8425 Series
Rev.3.1_01
2.2 RESET Voltage Detector
The RESET voltage detector monitors the output voltage V_OUT (VOUT pin voltage). The detection 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 a lower voltage than the detection level and “High” for a higher voltage than the
release level. RESET outputs the normal logic if the VOUT pin voltage is 1.0 V or more.
The S-8425 Series incorporates a RESET release delay circuit.
[RESET release delay time (t_DELAY)]
The interval from when the VOUT pin voltage exceeds the RESET release voltage value (+V_DET2) until the
output of the RESET pin is actually inverted is called the RESET release delay time.
V
VOUT
+VDET2
VRESET
t
tDELAY
Figure 7 Definition of RESET Release Delay Time (t_DELAY)
3. Switch Unit
The switch unit consists of the V_SW1 and V_{SW2 VIN}
detectors, a switch controller, voltage regulator 2,
and switch transistor M1 (see Figure 8 Switch
Unit).
VOUT
M1
REG2
VBAT
3.1 V_SW1 Detector
The V_SW1 detector monitors the power supply
voltage VIN and sends the results of detection to
the switch controller. The detection voltage
(VSW1) can be set to 77 ±2% or 85 ±2% of the CS
release voltage +VDET1.
Switch
controller
VSW1
detector
VSW2
detector
Figure 8 Switch Unit
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