S-19500A03A-E8T1U4 Datasheet, PDF (34/52 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
3. 4 Watchdog input circuit
By inputting a rising edge to the WI pin, the watchdog timer detects a trigger. The S-19500/19501 Series has a
built-in watchdog input circuit which contains a band pass filter in the WI pin, and detects a rising edge which
satisfies an input condition as a trigger signal. Refer to *2 and Figure 4 in " Recommended Operation
Conditions".
During the operation of the watchdog timer, a trigger is detected only when the DLY pin voltage is in VDU to VDWL
and while the discharge operation of CDLY is being performed. Refer to "3. Watchdog timer block" in
" Operation" for details. The signal input from a monitored object by the watchdog timer to the watchdog timer
should be input with a time interval which is sufficiently shorter than the watchdog trigger time (tWI,tr).
Caution Under a noisy environment, the watchdog input circuit may detect the noise as a trigger signal.
Sufficiently evaluate with the actual application to confirm that a trigger is detected only in the
intended signal.
3. 5 Watchdog output circuit
The output form of the WO pin is Nch open-drain. The WO pin can output a signal without an external pull-up
resistor since it has a built-in resistor to pull up to the VOUT pin internally.
Do not connect to the pin other than VOUT pin when connecting an external pull-up resistor to the WO pin.
In the S-19500 Series, the watchdog output pin is prepared as the WO / RO pin.
Caution Define the external pull-up resistance by sufficient evaluation including the temperature
characteristics under the actual usage conditions.
34