S-19500A03A-E8T1U4 Datasheet, PDF (25/52 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
Rev.1.2_01
S-19500/19501 Series
3. Watchdog timer block
3. 1 Watchdog trigger time (tWI,tr)
The watchdog trigger time is the time period from when the watchdog timer initiates the detection of a trigger
signal to when a time-out is detected and the WO pin output changes to "L" (Refer to Figure 38). This value
changes according to CDLY. tWI,tr is determined by a built-in constant current which charges CDLY, the charge
detection threshold of the DLY pin, and the capacitance of CDLY. It is calculated by using the following equation.
tWI,tr = CDLY ×
(VDU − VDWL)
ID,dcha
VDLY
VDU
VDWL
t
tWI,tr
tWD,l
VWO
tWD,p
t
Figure 38 Watchdog Trigger Time
3. 2 Watchdog output "L" time (tWD,I)
The watchdog output "L" time is the time period when the WO pin continues "L" after the watchdog timer detects a
time-out. This value changes according to CDLY, and is calculated by using the following equation.
tWD,I = CDLY ×
(VDU − VDWL)
ID,dcha
3. 3 Watchdog output pulse period (tWD,p)
The watchdog output pulse period is the period of the continuous rectangular wave that appears in the WO pin
when the watchdog timer repeats the detection of a time-out. It is calculated by using the following equation.
tWD,p = tWI,tr + tWD,I
Caution
Values shown in "3. Watchdog timer block" in " Electrical Characteristics" and " Characteristics
(Typical Data)" are values when VOUT decreases to −VDET or lower and the discharge operation of CDLY
due to the detector operation is not performed.
The discharge operation of CDLY could be performed when VOUT decreases to −VDET or lower, at that
time, tWI,tr, tWD,I and tWD,p may be changed.
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