HA1835P/HA1848P

Watchdog Timer

ADE-204-059 (Z)
Rev. 0
Dec. 2000

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.

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 HA1835P/HA1848P

Block Diagram

VCC RCS Vout

Q

C1
VCC CS VCONT Vout HA1835P
11 12 10 6

Current
Limiter
5 kΩ
Reference
Voltage Error
Amp
9 Comp *

8 Vadj
2 kΩ

14 RES

Fail Detector Power on Reset Detector

P-RUN 3 (Band Pass Filter) Reset Signal Oscillator 13 RES

7 4 5 1 2
Rf Cf RR CR
300 kΩ 0.01 µF 560 kΩ 0.1 µF

GND
Note: HA1848P: 9 pin is non connection.

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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
Output current 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
Note: Ta ≤ 77°C. If Ta > 77°C, derate by 8.3 mW/°C.

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 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 Output voltage Vout1 4.75 5.00 5.25 V VCC = 6 to 17.5 V, Iout = 0.5 A

section 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 δVout/δT — –0.6 — mV/°C

coefficient

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

Reset circuit Reset terminal low-level VOL1 — — 0.4 V IOL = 2 mA

section voltage

Reset terminal IOH1 — — 5.0 µA VOH = 5 V

leakage current IOH3 — — 30 µA VOH = 17.5 V

Reset time 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

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HA1835P/HA1848P

Test Circuit

2SB857D

S2
3 10
12 CS P-RUN VCONT Vout 6 + C2
RSC 0.2 Ω 5 kΩ 5 kΩ − 100 µF

11 VCC RES 14
S1 HA1835P
RES 13
VBatt
Vadj 8
Rf Cf GND RR CR Counter
4 5 7 1 2

300 kΩ 0.01 µF 560 kΩ 0.1 µF

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 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.

5 ⋅ Vout − 7.14
R (Vout − Vadj) ≈ (kΩ)
5 − Vout
7.14
R (Vadj − GND) ≈ (kΩ)
Vout − 5

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:

0.3 V
RSC ≈ (at Ta = 25°C)
Iout (Limit)

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.

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HA1835P/HA1848P

Application Circuit Example

RSC Q
VBatt 2SB857D
VReg
+ C1 0.2 Ω + C2
− 100 µF
− 10 µF
11 12 10 6 5 kΩ
VCC CS VCONT Vout
VCC
RES 13 RES

Microcomputer
system

P-RUN 3 I/O port

Rf Cf GND RR CR
4 5 7 1 2
Rf Cf RR CR
300 kΩ 0.01 µF 560 kΩ 0.1 µF

System burst
VCC

P-RUN

toff tRL
RES tRH
ton Reset output signal 3 Hz

Power-on reset signal

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 HA1835P/HA1848P

Characteristic Curves

Output voltage VOUT (V) 4

Ta = 25°C

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
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Ta = 25°C
Output voltage VOUT (V)

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
VIN = 12 V
Output voltage VOUT (V)

IOUT = 1 A

5.0

4.9
−50 0 50 100
Ambient temperature Ta (°C)
Figure 3 Output Voltage vs. Ambient Temperature

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HA1835P/HA1848P

Automatic reset pulse high time

200 µF

µF
.1
VIN = 12 V =0

22
0.
Ta = 25°C CR

=
tRH (ms)

R
C
7µ
F
100 4
= 0.0
CR

0
50 k 100 k 200 k 500 k 1M
Resistor RR (Ω)
Figure 4 Automatic Reset Pulse High Time vs. Resistor
Automatic reset pulse low time

200
VIN = 12 V
2µ
Ta = 25°C F
.2
tRL (ms)

=0
CR
100

.1 µF
CR = 0
47 µF
C R = 0.0
0
50 k 100 k 200 k 500 k 1M
Resistor RR (Ω)
Figure 5 Automatic Reset Pulse Low Time vs. Resistor
Power-on reset time ton (ms)

µF
µF

100 1
0.
22

=
VIN = 12 V
0.

CR
=

Ta = 25°C
R
C

7µ
F
50 4
= 0.0
CR

0
50 k 100 k 200 k 500 k 1M
Resistor RR (Ω)
Figure 6 Power-on Reset Time vs. Resistor

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 HA1835P/HA1848P

5k

Ta = 25°C
VIN = 12 V
2k
Clock pulse frequency f (Hz)

1k

500
Allowable operation
clock pulse duty
cycle
200

A B
100
B
Duty =
A+B
50

30
40 60 0 80 20
100
Clock pulse duty cycle (%)
Figure 7 Clock Pulse Frequency vs. Clock Pulse Duty Cycle

Ta = 25°C
20 k VIN = 12 V
Duty = 50%
10 k
System run-away
sense region
5k
Clock pulse frequency f (Hz)

2k

1k

500
Normal operation region

200

100

50
System run-away
sense region
20
100 k 200 k 500 k
Resistor Rf (Ω)
Figure 8 Clock Pulse Frequency vs. Resistor

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HA1835P/HA1848P

Package Dimensions

Unit: mm
19.20
20.32 Max
14 8

7.40 Max
6.30
1 7
1.30

2.39 Max 7.62

2.54 Min 5.06 Max

0.51 Min

+ 0.10
2.54 ± 0.25 0.48 ± 0.10 0.25 – 0.05

0° – 15°

Hitachi Code DP-14

JEDEC Conforms
EIAJ Conforms
Mass (reference value) 0.97 g

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 HA1835P/HA1848P

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intellectual property rights, in connection with use of the information contained in this document.
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received the latest product standards or specifications before final design, purchase or use.
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contact Hitachi’s sales office before using the product in an application that demands especially high
quality and reliability or where its failure or malfunction may directly threaten human life or cause risk
of bodily injury, such as aerospace, aeronautics, nuclear power, combustion control, transportation,
traffic, safety equipment or medical equipment for life support.
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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
beyond the guaranteed ranges. Even within the guaranteed ranges, consider normally foreseeable
failure rates or failure modes in semiconductor devices and employ systemic measures such as fail-
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