HA16117F Series
CMOS Watchdog Timer
Description
The HA16117F Series of ICs make a micro-processor (MPU) system fail-safe by monitoring its power
supply to detect voltage drops, and monitoring a P-RUN (program running) pulse to detect system crashes.
Also referred to as watchdog timers, these devices are essential in systems that aim for high levels of crash
protection. Fabricated by a CMOS process, they consume little power and are ideally suited for battery-
operated systems.
These ICs are available in versions for industrial and communications equipment and automotive
applications, as well as for consumer products.
Functions
Power-on reset
Sends a
RES
signal to the MPU for a fixed time at power-on
Watchdog timer (WDT)
Monitors a P-RUN signal from the MPU and sends the MPU a
RES
signal if P-RUN departs from a
set frequency range
Auto-reset
Outputs
RES
signals to the MPU at clocked intervals while P-RUN remains abnormal
Supply voltage supervision
Outputs a low
RES
signal if the supply voltage (same as the MPU's V
CC
) falls below a low threshold
level (V
TL
). The threshold differs for different ICs in the series, allowing designers to choose an IC
matching system requirements (see ordering information)
Features
Low power consumption : Operating (ACC pin low) = 0.5 mW (Typ)
: Standby (ACC pin high) = 0.2 mW (Typ)
Watchdog timer on/off control by ACC input signal
Independent auto-reset high and low times (t
RH
and t
RL
)
Watchdog monitoring by frequency filtering (independent of duty cycle)
High-precision low voltage detection (
±
2%)
Space- and weight-saving 8-pin SOP package