Datasheet HA1835P Datasheet (HIT)

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; VCC = 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

R
C

P-RUN

Rf
Cf

Vout

GND

1

R

2

R

3
4
5
6
7

14
13
12
11
10

RES

RES

CS
V

CC

V

CONT

Comp *

9

Vadj

8

(Top View)

Note: HA1848P: 9 pin is non connection.

Pin Functions

Pin No. Symbol Functions

1R

2C

R

R

3 P-RUN Clock pulse input terminal for watchdog timer
4 Rf Frequency band width of filter circuit depends on resistance connected to Rf

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

7 GND Ground
8 Vadj Output voltage fine tuning terminal
9 Comp Phase compensation terminal: Connect less than 100 pF capacitor between V

10 V
11 V

CONT

CC

12 CS Connect current sense resistor, which protects the external PNP transistor,

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.

Reset pulse width depends on resistance connected to R

R

Recommended range: 100 kΩ to 1 MΩ
Reset pulse width depends on capacitance connected to C

R

Recommended range: 100 kΩ to 500 kΩ

voltage for internal circuit

and Comp. HA1848P is non connection
External PNP transistor's base control terminal
Supply voltage terminal: Operating supply voltage range is 6 V to 30 V

between V

and CS

CC

CC

2

Block Diagram

V

CC

C

1

Reference

Voltage

11

R

V

CC

Current

Limiter

CS

12

Error
Amp

CS

Q

10

V

CONT

HA1835P/HA1848P

Vout

Vout HA1835P

6

5 kΩ

2 kΩ

9 Comp *

8 Vadj

14 RES

Fail Detector

3P-RUN

(Band Pass Filter)

4 5

Rf
300 kΩCf0.01 µF

Power on Reset Detector

Reset Signal Oscillator

1 27

R

R

560 kΩ

GND

Note: HA1848P: 9 pin is non connection.

C

R

0.1 µF

13 RES

3

HA1835P/HA1848P

Absolute Maximum Ratings (Ta = 25°C)

Item Symbol Rating Unit

Supply voltage V
P-RUN input voltage V
Output voltage V

Output current I

Control terminal voltage V
Control terminal current I

CC

P-RUN

RES

V

RES

RES

I

RES

CONT

CONT

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.

30 V
–0.3 to Vout V

17.5 V

17.5 V
2mA
2mA
V

CC

V

20 mA

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 I

CC

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 δV
Load regulation δV
Ripple rejection R
Limiter operating current I
Output voltage temperature

Oline

Oload

REJ

CS

δVout/δT — –0.6 — mV/°C

coefficient
P-RUN input Low-level input voltage V
section High-level input voltage V

Low-level input current I

High-level input current I
Reset circuit

section

Reset terminal low-level

voltage

Reset terminal I

leakage current I
Reset time Power on time t

Clock off reset time t

Reset pulse low-level time t

Reset pulse high-level time t

V

IL

IH

IL

IH

OL1

OH1

OH3

on

off

RL

RH

— 6.3 12 mA VCC = 17.5 V (No load),

with PNP transistor

–50 — +50 mV VCC = 6 to 17.5 V, Iout = 1 A
–100 — +100 mV Iout = 10 mA to 0.5 A
40 75 — dB ei = 0.5 Vrms, fi = 1 kHz

1.0 — 2.0 A RSC = 0.2 Ω

— — 0.8 V

2.0 — — V
–120 –60 — µAVIL = 0 V
— 1.8 3.0 mA Vout = 5 V, VIH = 5 V
— — 0.4 V IOL = 2 mA

— — 5.0 µAVOH = 5 V
——30µAVOH = 17.5 V
80 130 200 ms Rf = 300 kΩ, RR = 560 kΩ,
60 130 220 ms Cf = 0.01 µF, CR = 0.1 µF
40 80 160 ms
50 100 200 ms

5

HA1835P/HA1848P

Test Circuit

S

12 CS Vout

0.2 Ω

R

SC

11 V

S

1

V

Batt

Rf

2

CC

4

3

P-RUN

Cf

5

2SB857D

10

V

CONT

HA1835P

GND

7

+

C

5 kΩ

5 kΩ

−

100 µF

2

RES 14

13

RES

Vadj68

R

R

1

C

R

2

Counter

300 kΩ

0.01 µF

560 kΩ

0.1 µF

6

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) ≈ (kΩ)

R (Vadj − GND) ≈ (kΩ)

5 ⋅ Vout − 7.14

5 − Vout

7.14

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:

R

SC

0.3 V

≈ (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.

7

HA1835P/HA1848P

Application Circuit Example

R

V

CC

SC

0.2 Ω
1211

CS

V

Batt

+

C

1

−

10 µF

Q

2SB857D

10

V

CONT

6

Vout

5 kΩ

13

RES RES

V

C

2

100 µF

Reg

+

−

V

CC

Microcomputer

system

Rf

4

Rf
300 kΩ

Cf

5

Cf

0.01 µF

GND

7

R

R

1

P-RUN

R

R

560 kΩ

C

2

3

R

C

R

0.1 µF

I/O port

System burst

V

CC

P-RUN

RES

t

on

Power-on reset signal

t

RL

t

off

t

RH

Reset output signal 3 Hz

8

Characteristic Curves

HA1835P/HA1848P

5

4

(V)

OUT

V

3

I

= 0.1 A

2

Output voltage

1

0

0510

OUT

0.5 A

1.0 A

Input voltage

Figure 1 Output Voltage vs. Input Voltage

6

(V)

OUT

4

V

Ta = 25°C

VIN (V)

Ta = 25°C

Ω

2

R = 0.5

0.2 Ω

Output voltage

0

012

Output current

I

(A)

OUT

Figure 2 Output Voltage vs. Output Current

5.1

(V)

OUT

V

5.0

VIN = 12 V

= 1 A

I

OUT

Output voltage

4.9

−50 500 100

Ambient temperature

Ta (°C)

Figure 3 Output Voltage vs. Ambient Temperature

9

HA1835P/HA1848P

200

(ms)

100

RH

t

0

Automatic reset pulse high time

200

(ms)

100

RL

t

VIN = 12 V
Ta = 25°C

= 0.22 µF

R

C

C

200 k 500 k

Resistor R

R

(Ω)

Figure 4 Automatic Reset Pulse High Time vs. Resistor

V

= 12 V

IN

Ta = 25°C

C

= 0.1 µF

R

C

= 0.047 µF

R

= 0.22 µF

R

1 M50 k 100 k

0

Automatic reset pulse low time

Figure 5 Automatic Reset Pulse Low Time vs. Resistor

100

(ms)

on

VIN = 12 V
Ta = 25°C

50

0

Power-on reset time t

Figure 6 Power-on Reset Time vs. Resistor

Resistor RR (Ω)

= 0.22 µF

R

C

Resistor R

R

(Ω)

= 0.1 µF

C

R

= 0.047 µF

C

R

= 0.1 µF

R

C

= 0.047 µF

R

C

1 M50 k 100 k 200 k 500 k

1 M50 k 100 k 200 k 500 k

10

HA1835P/HA1848P

5 k

Ta = 25°C
V

= 12 V

IN

2 k

1 k

500

Allowable operation
clock pulse duty

200

Clock pulse frequency f (Hz)

100

50

30

0 20 40 60 80 100

Clock pulse duty cycle (%)

Figure 7 Clock Pulse Frequency vs. Clock Pulse Duty Cycle

cycle

Duty =

AB

B

A + B

Ta = 25°C

20 k

V

= 12 V

IN

Duty = 50%

10 k

5 k

2 k

1 k

500

System run-away
sense region

Normal operation region

200

Clock pulse frequency f (Hz)

100

50

System run-away
sense region

20

100 k 200 k 500 k

Resistor Rf (Ω)

Figure 8 Clock Pulse Frequency vs. Resistor

11

HA1835P/HA1848P

Package Dimensions

1

19.20

20.32 Max

1.30

Unit: mm

814

6.30

7.40 Max

7

2.54 ± 0.25

2.39 Max

0.48 ± 0.10

2.54 Min 5.06 Max

0.51 Min

Hitachi Code
JEDEC
EIAJ
Mass

7.62

+ 0.10

0.25

– 0.05

0° – 15°

(reference value)

DP-14
Conforms
Conforms

0.97 g

12

HA1835P/HA1848P

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for maximum rating, operating supply voltage range, heat radiation characteristics, installation
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