S-19500A03A-E8T1U4 Datasheet, PDF (21/52 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
 Selection of Watchdog Activation Threshold Current Adjustment Resistor (RWADJ,ext)
In the S-19500/19501 Series, the watchdog activation threshold current adjustment resistor (RWADJ,ext) can be
connected between the WADJ pin and the VSS pin to adjust the watchdog timer activation threshold current.
The set watchdog activation threshold current (IO,WDact(S)), the set watchdog deactivation threshold current (IO,WDdeact(S))
and the set watchdog activation hysteresis current (IO,WDhys(s)) are calculated by using following equations, respectively.
The watchdog activation threshold current (IO,WDact), the watchdog deactivation threshold current (IO,WDdeact) and the
watchdog activation hysteresis current (IO,WDhys) when the WADJ pin is open are shown in " Electrical
Characteristics".
IO,WDact(S) [mA] = IO,WDact [mA] ×
1 +

RWADJ,int [kΩ] 
RWADJ,ext [kΩ]_
IO,WDdeact(S) [mA] = IO,WDdeact [mA] × 1 +

RWADJ,int [kΩ] 
RWADJ,ext [kΩ]_
IO,WDhys(S) [mA] = IO,WDact(S) [mA] − IO,WDdeact(S) [mA]
Caution 1. The above equations will not guarantee successful operation. Perform thorough evaluation including
the temperature characteristics using an actual application to set the constants.
2. Mounted board layout should be made in such a way that no current flows into or flows from the
WADJ pin since the impedance of the WADJ pin is high, otherwise correct IO,WDact and IO,WDdeact may
not be provided.
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