Hitachi HA1835P Watchdog timer Datasheet

HA1835P/HA1848P
Watchdog Timer
Description
The HA1835P and HA1848P is a monolithic voltage regulator control designed for microcomputer
systems. In addition to the voltage regulator, it include watchdog timer function and power-on reset
function.
These ICs can perform many function in various microcomputer systems with few external parts.
Features
• Regulated power supply control function
 Wide area of operational voltage; V CC = 6 V to 30 V
 Available external PNP-type transistor, suited to any system power supply
 Built-in overcurrent limiter for external PNP-type transistor
 Output voltage can be adjusted exactry in the range from 4 V to 6 V
• Watchdog timer
 Internal bandpass filter control circuit (pulse width detect type) and reset signal oscillator
 Fail-safe utility
 Bandpass filter characteristics can be set by external resister (Rf) and capacitance (Cf)
• Automatic reset
 Automatic power-on reset
 Pulse generator characteristics can be set by external resistor (RR) and capacitance (CR)
 Alternative between RES and RES output
HA1835P/HA1848P
Pin Arrangement
RR
1
14
RES
CR
2
13
RES
P-RUN
3
12
CS
Rf
4
11
VCC
Cf
5
10
VCONT
Vout
6
9
Comp *
GND
7
8
Vadj
(Top View)
Note: HA1848P: 9 pin is non connection.
Pin Functions
Pin No.
Symbol
Functions
1
RR
Reset pulse width depends on resistance connected to RR
Recommended range: 100 kΩ to 1 MΩ
2
CR
Reset pulse width depends on capacitance connected to CR
3
P-RUN
Clock pulse input terminal for watchdog timer
4
Rf
Frequency band width of filter circuit depends on resistance connected to Rf
Recommended range: 100 kΩ to 500 kΩ
5
Cf
Frequency band width of filter circuit depends on capacitance connected to Cf
6
Vout
Connect to external PNP transistor's collector: This pin supplies 5 V regulated
voltage for internal circuit
7
GND
Ground
8
Vadj
Output voltage fine tuning terminal
9
Comp
Phase compensation terminal: Connect less than 100 pF capacitor between V CC
and Comp. HA1848P is non connection
10
VCONT
External PNP transistor's base control terminal
11
VCC
Supply voltage terminal: Operating supply voltage range is 6 V to 30 V
12
CS
Connect current sense resistor, which protects the external PNP transistor,
between V CC and CS
13
RES *
Reset pulse output terminal for low level reset type microcomputer
14
RES *
Reset pulse output terminal for high level reset type microcomputer
Note: RES and RES are open-collector output terminals, so connect a pull-up resistor of about 5 kΩ.
2
HA1835P/HA1848P
Block Diagram
RCS
VCC
Vout
Q
C1
11
VCC
12
CS
10
VCONT
Current
Limiter
Reference
Voltage
6
Vout
HA1835P
5 kΩ
Error
Amp
9 Comp *
8 Vadj
2 kΩ
14 RES
Fail Detector
(Band Pass Filter)
P-RUN 3
7
4
Power on Reset Detector
Reset Signal Oscillator
5
Rf
300 kΩ
1
Cf
0.01 µF
13 RES
2
RR
560 kΩ
CR
0.1 µF
GND
Note: HA1848P: 9 pin is non connection.
3
HA1835P/HA1848P
Absolute Maximum Ratings (Ta = 25°C)
Item
Symbol
Rating
Unit
Supply voltage
VCC
30
V
P-RUN input voltage
VP-RUN
–0.3 to Vout
V
Output voltage
VRES
17.5
V
VRES
17.5
V
I RES
2
mA
I RES
2
mA
Control terminal voltage
VCONT
VCC
V
Control terminal current
I CONT
20
mA
Power dissipation (Note)
PT *
400
mW
Operating temperature range
Topr
–40 to +85
°C
Storage temperature range
Tstg
–50 to +125
°C
Soldering temperature
Tsol
+260 (< 10 sec)
°C
Output current
Note: Ta ≤ 77°C. If Ta > 77°C, derate by 8.3 mW/°C.
4
HA1835P/HA1848P
Electrical Characteristics (VCC = 12 V, Vout = 5 V, Ta = 25°C)
Item
Symbol
Min
Typ
Max
Unit
Test Conditions
Power supply terminal current
ICC
—
6.3
12
mA
VCC = 17.5 V (No load),
with PNP transistor
Regulator
Vout1
4.75
5.00
5.25
V
VCC = 6 to 17.5 V, Iout = 0.5 A
Vout2
4.70
5.00
5.30
V
VCC = 6 to 17.5 V, Iout = 1 A
Line regulation
δVOline
–50
—
+50
mV
VCC = 6 to 17.5 V, Iout = 1 A
Load regulation
δVOload
–100
—
+100
mV
Iout = 10 mA to 0.5 A
Ripple rejection
RREJ
40
75
—
dB
ei = 0.5 Vrms, fi = 1 kHz
Limiter operating current
ICS
1.0
—
2.0
A
RSC = 0.2 Ω
Output voltage temperature
coefficient
δVout/δT
—
–0.6
—
mV/°C
P-RUN input Low-level input voltage
VIL
—
—
0.8
V
section
High-level input voltage
VIH
2.0
—
—
V
Low-level input current
IIL
–120
–60
—
µA
VIL = 0 V
High-level input current
IIH
—
1.8
3.0
mA
Vout = 5 V, VIH = 5 V
VOL1
—
—
0.4
V
IOL = 2 mA
Reset terminal
IOH1
—
—
5.0
µA
VOH = 5 V
leakage current
IOH3
—
—
30
µA
VOH = 17.5 V
Power on time
ton
80
130
200
ms
Rf = 300 kΩ, RR = 560 kΩ,
Clock off reset time
toff
60
130
220
ms
Cf = 0.01 µF, CR = 0.1 µF
Reset pulse low-level time
tRL
40
80
160
ms
Reset pulse high-level time
tRH
50
100
200
ms
Output voltage
section
Reset circuit Reset terminal low-level
section
voltage
Reset time
5
HA1835P/HA1848P
Test Circuit
2SB857D
S2
3
P-RUN
12 CS
RSC
10
VCONT
Vout 6
0.2 Ω
5 kΩ
RES 14
11 VCC
S1
HA1835P
RES 13
VBatt
Rf
4
Cf
5
300 kΩ
6
5 kΩ
GND
7
0.01 µF
RR
1
Vadj 8
CR
2
560 kΩ
0.1 µF
Counter
+ C2
− 100 µF
HA1835P/HA1848P
Functional Description
Voltage Regulator
The HA1835P, and HA1848P supplies 5 V regulated output from a wide VCC input range (VCC = 6 V to
17.5 V). The external PNP transistor should be selected according to the supply current demand of the
system. Connect a more than 100 µF capacitor between Vout and GND to realize the 5 V regulated output.
The resistor connected from the Vadj terminal to the Vout or GND terminal fine tunes the output voltage.
A resistor between Vadj and the Vout decreases the output voltage, and a resistor between Vadj and GND
increases the output voltage.
R (Vout − Vadj) ≈
5 ⋅ Vout − 7.14
5 − Vout
R (Vadj − GND) ≈
7.14
Vout − 5
(kΩ)
(kΩ)
Current Limiter
To protect the external transistor from overcurrent, connect a current-sense resistor between the CS
terminal and the VCC terminal. The value of this resistor should be:
RSC ≈
0.3 V
Iout (Limit)
(at Ta = 25°C)
Power-On Reset
The HA1835P, and HA1848P can output a reset pulse to start the microcomputer at power on (figure 6).
The external resistor RR and capacitor CR determine the power-on reset timing.
Note that RES and RES are open-collector terminals. They should therefore be connected to a pull-up
resistor of about 5 kΩ.
Watchdog Timer
The watchdog timer is a fail-safe function. It can reset the microcomputer system if the system runs out of
control. It does this be monitoring a pulse output by the system's software. It uses a bandpass filter to
determine whether the pulse frequency is within the system's normal frequency band (figure 7, 8). External
resistor and capacitor Rf and Cf determine the frequency range of the bandpass filter. If the pulse
frequency is not within the frequency band, the HA1835P, and HA1848P outputs a reset pulse.
7
HA1835P/HA1848P
Application Circuit Example
Q
2SB857D
RSC
VBatt
VReg
0.2 Ω
+ C1
− 10 µF
11
VCC
+ C2
− 100 µF
12
CS
10
VCONT
5 kΩ
6
Vout
RES 13
RES
VCC
Microcomputer
system
P-RUN 3
Rf
4
Cf
5
Rf
300 kΩ
GND
7
Cf
0.01 µF
RR
1
CR
2
RR
560 kΩ
CR
0.1 µF
System burst
VCC
P-RUN
toff tRL
RES
ton
Power-on reset signal
8
tRH
Reset output signal 3 Hz
I/O port
HA1835P/HA1848P
Characteristic Curves
Output voltage VOUT (V)
5
4
Ta = 25°C
3
IOUT = 0.1 A
2
0.5 A
1.0 A
1
0
0
5
10
Input voltage VIN (V)
Figure 1 Output Voltage vs. Input Voltage
Output voltage VOUT (V)
6
Ta = 25°C
4
R = 0.5 Ω
0.2 Ω
2
0
0
1
2
Output current IOUT (A)
Figure 2 Output Voltage vs. Output Current
5.1
Output voltage VOUT (V)
VIN = 12 V
IOUT = 1 A
5.0
4.9
−50
0
50
100
Ambient temperature Ta (°C)
Figure 3 Output Voltage vs. Ambient Temperature
9
10
µF
200
CR
µF
.1
=0
C
R
=
0.
22
VIN = 12 V
Ta = 25°C
7µ
F
100
CR
0
50 k
=
4
0.0
100 k
1M
200 k
500 k
Resistor RR (Ω)
Figure 4 Automatic Reset Pulse High Time vs. Resistor
200
VIN = 12 V
Ta = 25°C
2µ
CR
F
.2
=0
100
.1 µF
CR = 0
100 k
200 k
500 k
Resistor RR (Ω)
Figure 5 Automatic Reset Pulse Low Time vs. Resistor
0.
=
CR
0.
=
1M
µF
R
VIN = 12 V
Ta = 25°C
1
22
100
7µ
F
50
CR
0
50 k
47 µF
C R = 0.0
µF
0
50 k
C
Power-on reset time ton (ms)
Automatic reset pulse low time
tRL (ms)
Automatic reset pulse high time
tRH (ms)
HA1835P/HA1848P
100 k
=
200 k
500 k
Resistor RR (Ω)
Figure 6 Power-on Reset Time vs. Resistor
4
0.0
1M
HA1835P/HA1848P
5k
Ta = 25°C
VIN = 12 V
1k
500
Allowable operation
clock pulse duty
cycle
200
A B
100
Duty =
B
A+B
50
30
40
60
80
100
Clock pulse duty cycle (%)
Figure 7 Clock Pulse Frequency vs. Clock Pulse Duty Cycle
0
20
20 k
Ta = 25°C
VIN = 12 V
Duty = 50%
10 k
Clock pulse frequency f (Hz)
Clock pulse frequency f (Hz)
2k
System run-away
sense region
5k
2k
1k
500
Normal operation region
200
100
50
System run-away
sense region
20
100 k
200 k
Resistor Rf (Ω)
500 k
Figure 8 Clock Pulse Frequency vs. Resistor
11
HA1835P/HA1848P
Package Dimensions
Unit: mm
19.20
20.32 Max
8
6.30
7.40 Max
14
1.30
7
2.54 ± 0.25
0.48 ± 0.10
0.51 Min
2.39 Max
2.54 Min 5.06 Max
1
7.62
+ 0.10
0.25 – 0.05
0° – 15°
Hitachi Code
JEDEC
EIAJ
Mass (reference value)
12
DP-14
Conforms
Conforms
0.97 g
HA1835P/HA1848P
Cautions
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contact Hitachi’s sales office before using the product in an application that demands especially high
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4. Design your application so that the product is used within the ranges guaranteed by Hitachi particularly
for maximum rating, operating supply voltage range, heat radiation characteristics, installation
conditions and other characteristics. Hitachi bears no responsibility for failure or damage when used
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failure rates or failure modes in semiconductor devices and employ systemic measures such as failsafes, so that the equipment incorporating Hitachi product does not cause bodily injury, fire or other
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