X4003, X4005 pdf datasheet (CP

These devices combine three popular functions; Power-on
Reset Control, Watchdog Timer and Supply Voltage
Supervision. This combination lowers system cost, reduces
board space requirements and increases reliability.
Applying power to the device activates the power-on reset
circuit which holds RESET/RESET active for a period of
time. This allows the power supply and oscillator to stabilize
before the processor can execute code.
The Watchdog Timer provides an independent protection
mechanism for microcontrollers. When the microcontroller
fails to restart a timer within a selectable time out interval,
the device activates the RESET/RESET signal. The user
selects the interval from three preset values. Once selected,
the interval does not change, even after cycling the power.
The device’s low VCC detection circuitry protects the user’s
system from low voltage conditions, resetting the system
when VCC falls below the minimum VCC trip point.
RESET/RESET is asserted until VCC returns to proper
operating level and stabilizes. Five industry standard VTRIP
thresholds are available; however, Intersil’s unique circuits
allow the threshold to be reprogrammed to meet custom
requirements, or to fine-tune the threshold for applications
requiring higher precision.