S-19500A03A-E8T1U4 Datasheet, PDF (33/52 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. 3 Watchdog enable circuit
S-19500 Series has a built-in watchdog Enable circuit that switches Enable or Disable of the watchdog timer due
to input to the WEN pin. When inputting "L" to the WEN pin, the watchdog timer becomes Disable and stops the
output current detection operation and monitoring activation. When inputting "H" to the WEN pin, the watchdog
timer becomes Enable. The watchdog timer monitoring activation is performed depending on the connection of the
WADJ pin.
The internal equivalent circuit of the WEN pin is configured as shown in Figure 46, and is pulled down internally
by the constant current source. For this reason, the WEN pin is set to "L" when using the WEN pin in the floating
status, and the watchdog timer becomes Disable. However, in order that the watchdog timer become Disable
certainly, connect the WEN pin to GND so that "L" is input to the WEN pin certainly, since the impedance of the
WEN pin is high when using the WEN pin in the floating status.
In order to fix the watchdog timer to Enable, connect the WEN pin to the VOUT pin so that "H" is input to the WEN
pin.
Table 16 shows the relation between status of each pins and the watchdog timer.
Table 16
WEN Pin
Input Logic
WADJ Pin Connection^*1
Output
Current^*2
Output Current
Watchdog Timer
WO Pin
Detection Circuit Monitoring Activation Input Logic
"H"
Open, or connect to VSS
pin via external resistor^*3
"H"
Operate
Activate
"H" or "L"
"H"
Open, or connect to VSS
pin via external resistor^*3
"L"
Operate
Deactivate
"H"
"H"
Connect to VOUT pin via
resistor of 270 kΩ
Don't care Stop
"H"
Connect to VSS pin
Don't care Stop
Activate
Deactivate
"H" or "L"
"H"
"L"
Don't care
Don't care Stop
Deactivate
"H"
*1. Refer to "1. WADJ pin" in " Pin Functions".
*2. Output current "H": IOUT > IO,WDact
Output current "L": IOUT < IO,WDdeact
*3. Refer to " Selection of Watchdog Activation Threshold Current Adjustment Resistor (RWADJ,ext)".
VOUT
WEN
VSS
Figure 46
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