HA16117F Datasheet, PDF (1/31 Pages) Hitachi Semiconductor – CMOS Watchdog Timer

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