HA16117F Datasheet, PDF (3/31 Pages) Hitachi Semiconductor – CMOS Watchdog Timer

Block Diagram
HA16117F Series
1
5V
V_CC
2.52 (117FA)
2.36 (117FB) Low voltage detector
GND
6
2.20 (117FC)
−
1
+
≈1.25 V
COMP.
GND
0.1 µ
4 ^CR
Power-on and auto-reset circuit
(*I₁ < I₂)
SW2
I₂ adjustment
I₂
I₁
SW1
−
+
COMP.
RES
5
to Micro-
computer
R₁
510 k
R₂
750 k
Tadj
8
(SW1 and SW2 are active high)
Watchdog timer
Watchdog filter (f-duty converter)
P-RUN
2
1/2 frequency ^{W.D in}
divider
W.D out
duty (%)
n
Normal range
duty 50%
f_L/2
f_H/2
W.D in frequency (Hz)
W.D out
duty n%
PULSE from I/O port
3 ^CF
0.01 µ
Mode
Operating
Standby
ACC Voltage
Low
High
Function
Low voltage detection and WDT
Low voltage detection
Note: The power-on reset circuit operates in both operating and standby modes.
ACC
7
Operating: "Low"
Standby: "High"
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 I₂ that discharges C_R, and a comparator.
3