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
HA16117F Series
Ordering Information
The HA16117F Series includes three ICs with different low threshold levels (V
TL
).
Type No.
HA16117FPA/FPAJ
HA16117FPB/FPBJ
HA16117FPC/FPCJ
Low Threshold Voltage (V
TL
)
4.4 V Typ
4.2 V Typ
4.0 V Typ
Pin Arrangement
V
CC
P-RUN
C
F
C
R
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
V
CC
P-RUN
C
F
C
R
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 t
ON
for power-on reset and t
OFF
, t
RH
,
and t
RL
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 t
RH
and t
OFF
(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
V
CC
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
C
R
Power-on and auto-reset circuit
(*I
1
< I
2
)
SW2
I
2
adjustment
I
2
I
1
−
+
5
to Micro-
computer
COMP.
SW1
R
1
510 k
8
R
2
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
f
L
/2
f
H
/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
C
F
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 I
1
that charges the
external capacitor C
R
, a current source I
2
that discharges C
R
, 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 I
2
in the multivibrator, the higher the duty cycle of the watchdog filter
output, the shorter the time during which I
2
discharges C
R
. If the duty cycle is high enough then C
R
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
Operating temperature range
Storage temperature
Note:
Symbol
V
CC
V
P
V
ACC
I
RES
P
T
Topr
Tstg
HA16117FPA/FPB/FPC
–0.3 to +14
V
CC
14
10
300
–30 to +85
–55 to +125
HA16117FPAJ/FPBJ/FPCJ
–0.3 to +14
V
CC
14
10
300
–40 to +85
–55 to +125
Unit
V
V
V
mA
mW
°C
°C
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 7.14 mW/°C.
40mm
Substrate
Permissible dissipation P
T
(mW)
0.8 mm ceramic or
1.5 mm epoxy
400
300
200
100
85°C
0
−30 −20
0 20 40 60 80 100
Ambient operating temperature range Ta (°C)
83°C
−7.14
mW/°C
(30% wiring density)
4
HA16117F Series
Electrical Characteristics
(V
CC
= 5 V, Ta = 25°C, C
F
= 0.01
µF,
C
R
= 0.1
µF,
R
1
= 510 kΩ, R
2
= 750 kΩ)
Item
General
Operating supply current
Symbol
I
CC1
I
CC2
Standby supply current
Low
voltage
detector
Low voltage
threshold
level
HA16117FPA/FPAJ
I
STBY
V
TL
Min
—
—
—
4.3
Typ
100
200
43
4.4
Max
—
600
100
4.5
Unit
µA
µA
µA
V
Test Conditions
V
ACC
= 0 V,
f
P-RUN
= 100 Hz
V
ACC
= 0 V,
f
P-RUN
= 20 kHz
V
ACC
= 12 V
When V
CC
drops
HA16117FPB/FPBJ
HA16117FPC/FPCJ
Hysteresis width
ACC
Low input voltage
High input voltage
P-RUN
input
WDT
Low input voltage
High input voltage
Power-on reset time
Reset-clock off time
Reset low time
Reset high time
Low setup time
High setup time
RES
output
RES
low voltage
RES
high voltage
Reset function starting voltage
Constant
range
Constant range of R
1
and R
2
V
HYS
V
IL1
V
IH1
V
IL2
V
IH2
t
ON
t
OFF
*
1
t
RL
t
RH
t
SL
t
SH
V
OL
V
OH
V
RES
K
V
CCRNG
4.1
3.9
50
—
2.0
—
2.0
24
78
12
36
1
—
—
—
—
0.55
V
TL
4.2
4.0
100
—
—
—
—
40
130
20
60
—
—
—
V
CC
0.8
0.6
—
4.3
4.1
150
0.8
—
0.8
—
56
182
28
84
—
1
0.4
—
1.4
0.8
6.0
V
V
mV
V
V
V
V
ms
ms
ms
ms
ms
ms
V
V
V
—
V
K =R
2
/ (R
1
+ R
2
)
I
OL
= 1 mA
Open
P-RUN pin = 0 V
Operating supply voltage range
Note:
1. Reset-clock off time t
OFF
is provided a shown in the under figure.
f = 500 Hz, Duty = 50%
P-RUN
RES
t
OFF
5
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