S-19500A03A-E8T1U4 Datasheet, PDF (32/52 Pages) Seiko Instruments Inc – CMOS VOLTAGE REGULATOR WITH WATCHDOG TIMER AND RESET FUNCTION

FOR AUTOMOTIVE 125°C OPERATION HIGH-WITHSTAND VOLTAGE CMOS VOLTAGE REGULATOR WITH WATCHDOG TIMER AND RESET FUNCTION
S-19500/19501 Series
Rev.1.2_01
Depending on the output current (IOUT) of the regulator, the watchdog timer monitoring activation is as follows.
(1) When IOUT of the regulator is the watchdog activation threshold current (IO,WDact) or more, the WADJ pin voltage
(VWADJ) is higher than the reference voltage (Vref), and the output of the comparator (C1) is "H". At this time, the
watchdog timer initiates the monitoring activation.
(2) When IOUT decreases to the watchdog deactivation threshold current (IO,WDdeact) (point A in Figure 45) or less,
VWADJ decreases to Vref or less and the output of C1 is "L". At this time, the watchdog timer deactivates the
monitoring. Even if IOUT increases, the watchdog timer continues the monitoring deactivation when IOUT is within
less than IO,WDact
(3) If IOUT further increases to IO,WDact (point B in Figure 45) or more, VWADJ increases to Vref or higher and the
output of C1 is "H". And then, the watchdog timer initiates the monitoring activation.
VIN
VOUT
+
Reference voltage ^−
circuit
WEN
WADJ
R_WADJ,ext
VSS
R_WADJ,int
V_WADJ
Reference
voltage
V_ref
circuit
C1
+
−
WDT
circuit
Figure 44 Operation of Output Current Detection Circuit
(1)
(2)
(3)
Watchdog activation
A
hysteresis current
I_OUT
B
Watchdog activation threshold current (I_O,WDact)
Watchdog deactivation threshold current (I_O,WDdeact)
(I_O,WDhys)
0 mA
WDT
WDT
WDT
monitoring monitoring monitoring
activation deactivation activation
Caution
Remark
Figure 45 Autonomous Watchdog Operation Function
Due to detecting IOUT of the regulator, current flows through the registors connected to the WADJ pin
(RWADJ,ext and RWADJ,int). Therefore, the WADJ pin voltage (VWADJ) may fluctuate since the current
flowing through RWADJ,ext and RWADJ,int also changes in the same way if the output current changes
transiently. VWADJ at that time should be evaluated with the actual device.
IO,WDact, IO,WDdeact and IO,WDhys can be adjusted by connecting RWADJ,ext to the WADJ pin. Refer to
" Selection of Watchdog Activation Threshold Current Adjustment Resistor (RWADJ,ext)" for the detail.
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