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HA16117F Dataheets PDF



Part Number HA16117F
Manufacturers Hitachi Semiconductor
Logo Hitachi Semiconductor
Description CMOS Watchdog Timer
Datasheet HA16117F DatasheetHA16117F Datasheet (PDF)

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 batteryoperated systems. These ICs are avail.

  HA16117F   HA16117F


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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 batteryoperated 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 VCC) falls below a low threshold level (VTL). 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 (tRH and tRL) • Watchdog monitoring by frequency filtering (independent of duty cycle) • High-precision low voltage detection (±2%) • Space- and weight-saving 8-pin SOP package HA16117F Series Ordering Information The HA16117F Series includes three ICs with different low threshold levels (VTL). Type No. HA16117FPA/FPAJ HA16117FPB/FPBJ HA16117FPC/FPCJ Low Threshold Voltage (VTL) 4.4 V Typ 4.2 V Typ 4.0 V Typ Pin Arrangement VCC P-RUN CF CR 1 2 3 4 8 7 6 5 Tadj ACC GND RES (Top view) Pin Description Pin No. 1 2 3 4 5 6 7 8 Symbol VCC P-RUN CF CR RES GND ACC Tadj * Function Power supply voltage input Watchdog timer (WDT) input Connected capacitor C F determines WDT filter characteristic (normal frequency range) Connected capacitor C R determines tON for power-on reset and tOFF, t RH, and tRL for auto-reset Reset signal output from WDT and voltage supervision circuits Ground WDT on/off control input (on when ACC is low) For adjusting tRH and tOFF (divide V CC to get the adjustment voltage) Note: The low-voltage threshold cannot be modified by changing the external resistors connected to the Tadj pin. 2 HA16117F Series Block Diagram 5V GND VCC 1 2.52 (117FA) 2.36 (117FB) 2.20 (117FC) Low voltage detector − + 6 1 GND ≈1.25 V COMP. RES 0.1 µ 4 CR Power-on and auto-reset circuit (*I1 < I2) SW2 I2 adjustment I2 I1 − + 5 to Microcomputer COMP. SW1 R1 510 k 8 R2 750 k Tadj (SW1 and SW2 are active high) Watchdog timer Watchdog filter (f-duty converter) W.D out duty (%) Normal range W.D out fL/2 fH/2 duty n% P-RUN 1/2 frequency W.D in 2 divider duty 50% n W.D in frequency (Hz) 3 PULSE from I/O port Mode Operating Standby ACC Voltage Low High Function Low voltage detection and WDT Low voltage detection CF 0.01 µ 7 ACC Operating: "Low" Standby: "High" Note: The power-on reset circuit operates in both operating and standby modes. The HA16117F consists of a low voltage detector, power-on and auto-reset circuit, and watchdog timer. Low Voltage Detector Uses a reference voltage source (≈ 1.25 V) and high-precision comparator to detect drops in the supply voltage. Power-On and Auto-Reset Circuit Generates the RES waveform, using a multivibrator consisting of a current source I1 that charges the external capacitor C R, a current source I 2 that discharges CR, and a comparator. 3 HA16117F Series Watchdog Timer Reshapes the P-RUN signal (programming-running pulse) from the MPU to obtain a 50% duty cycle, then converts frequency to duty cycle in the watchdog filter (WD filter). The watchdog filter is a bandpass filter. The duty cycle of the filter output is highest in the normal frequency range of P-RUN. The watchdog filter output controls I2 in the multivibrator, the higher the duty cycle of the watchdog filter output, the shorter the time during which I2 discharges CR. If the duty cycle is high enough then CR is held at a high potential, preventing the multivibrator from firing, and the RES output remains high. Absolute Maximum Ratings (Ta = 25°C) Ratings Item Power supply voltage P-RUN input voltage ACC input voltage RES output current Permissible dissipation * 1 Symbol VCC VP VACC I RES PT Topr Tstg HA16117FPA/FPB/FPC –0.3 to +14 VCC 14 10 300 –30 to +85 –55 to +125 HA16117FPAJ/FPBJ/FPCJ –0.3 to +14 VCC 14 10 300 –40 to +85 –55 to +125 Unit V V V mA mW °C °C Operating temperature range Storage temperature Note: 1. This is the value when mounted on a glass epoxy substrate with 30% wiring density, up to an ambient temperature of 83 ° C. Above that temperature, derate by 7.1.


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