Allegro A3425LK-TK, A3425LK Datasheet

The A3425LK dual Hall-effect switch is an extremely

temperature-stable and stress-resistant sensor especially suited for use in

digital-encoder systems in the harsh environments of automotive or
industrial applications over extended temperature ranges to +150°C.

Superior high-temperature performance is made possible through
dynamic offset cancellation, which reduces the residual offset voltage
normally caused by device overmolding, temperature dependencies, and
thermal stress. This device also eliminates the major manufacturing

hurdles encountered in fine-pitch direction-detection applications,
namely maintaining accurate mechanical location between the two active
Hall elements. Here, the two Hall elements are photolithographically
aligned to better than 1 µm, as contrasted with 100 µm or worse me­chanical location tolerance when manufactured discretely. The
A3425LK is an ultra-sensitive device optimized for use with high­density ring magnets.

The device includes on a single silicon chip a voltage regulator, two
independent chopper-stabilized Hall-voltage generators , two small­signal amplifiers, two Schmitt triggers, and two short-circuit protected
open-collector outputs to sink up to 30 mA each. An on-board regulator
permits operation with supply voltages of 3.3 to 26.5 volts. With
suitable output pull ups, it can be used directly with bipolar or MOS
logic circuits.

The A3425LK dual Hall-effect switch is supplied in a 4-pin plastic
SIP for operation over a temperature range of -40°C to +150°C. A
similar device, with on-chip logic processing specifically for direction
detection applications, in a 5-pin SIP, is the A3422LKA.

FEATURES

■ Two Matched Hall Switches On A Single Substrate

■ 1 mm Sensor-to-Sensor Spacing

■ Superior Temperature Stability

■ Resistant to Physical Stress

■ Output Short-Circuit Protection

■ Operation From Unregulated Supply

■ Reverse Battery Protection

■ Solid-State Reliability

■ Integrated ESD Protection on Outputs and Supply

Data Sheet

27651.20

PRELIMINARY INFORMATION

(subject to change without notice)

August 21, 2000

Pinning is shown viewed from branded side.

DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE,

BIPOLAR HALL-EFFECT SWITCH

3425

ABSOLUTE MAXIMUM RATINGS

at TA = +25°C

Supply Voltage, VCC........................ 26.5 V

Reverse Battery Voltage, V

RCC

.......... -18 V

Zener Current, IZ............................ 100 mA

Magnetic Flux Density, B ........... Unlimited

Output Off Voltage, V

OUT

.................... V

CC

Output Current, I

OUT

........................ 30 mA

Reverse Output Current, I

OUT

........ -50 mA

Package Power Dissipation, PD. See Graph

Junction Temperature, TJ............... +170°C

Operating Temperature Range,

TA, ............................ -40°C to +150°C

Storage Temperature Range,

TS.............................. -65°C to +170°C

Always order by complete part number, e.g., A3425LK .

Dwg. PH-017

1

SUPPLY

V

CC

4

GROUND

32

X

OUTPUT

2

OUTPUT

1

X

3425

DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

2

FUNCTIONAL BLOCK DIAGRAM

Copyright © 2000, Allegro MicroSystems, Inc.

OUTPUT

1

<1Ω

X

DYNAMIC

OFFSET CANCELLATION

REG.

TO ALL

SUBCIRCUITS

SUPPLY

CONTROL

CURRENT

LIMIT

SAMPLE

& HOLD

LOW-PASS

FILTER

Dwg. FH-020-7

GROUND

OUTPUT

2

<1Ω

X

DYNAMIC

OFFSET CANCELLATION

CONTROL

CURRENT

LIMIT

SAMPLE

& HOLD

LOW-PASS

FILTER

1

2

3

4

E1

E2

75 100 125 150 175

1.0

0.2

0

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

AMBIENT TEMPERATURE IN °C

0.8

0.6

0.4

50

Dwg. GH-001-1

250

FREE AIR, R = 177°C/W

θJA

-25

3425

DUAL, CHOPPER-STABILIZED,

ULTRA-SENSITIVE,

BIPOLAR HALL-EFFECT SWITCH

www.allegromicro.com

3

ELECTRICAL CHARACTERISTICS over operating temperature range, each switch tested
separately (unless otherwise specified).

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Supply Voltage Range V

CC

Operating, TJ < 170°C

1

3.3 – 26.5 V

Output Leakage Current I

OFF

V

OUT

= 18 V, B < B

RP

– <1.0 10 µA

Output Saturation Voltage V

OUT(SAT)

I

OUT

= 20 mA, B > B

OP

– 225 400 mV

Output Current Limit I

OM

B > B

OP

30 – 55 mA

Chopping Frequency f

C

– 340 – kHz

Output Rise Time t

r

RL = 820 Ω, CL = 10 pF – 110 – ns

Output Fall Time t

f

RL = 820 Ω, CL = 10 pF – 55 – ns

Total Supply Current I

CC

Both outputs off, VCC ≤ 26.5 V – 3.8 6.0 mA

Both outputs on, VCC ≤ 26.5 V – 7.5 10 mA

Reverse Battery Current I

CC

V

RCC

= -18 V – 2.0 15 mA

Zener Voltage VZ + V

D

ICC = 15 mA, TA = 25°C 283337 V

Zener Impedance zz + z

D

ICC = 15 mA, TA = 25°C – 50 100 Ω

NOTES:1. Supply voltage is limited by allowable package power dissipation as a function of ambient temperature.

2. BOP = operate point (output turns on); BRP = release point (output turns off).

3. Typical Data is at TA = +25°C and VCC = 12 V and is for design information only.

MAGNETIC CHARACTERISTICS over operating supply voltage and temperature ranges, each
switch tested separately (unless otherwise specified).

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Operate Point B

OP1

– 8.0 24 G

B

OP2

–1124G

Release Point B

RP1

-24 -11 – G

B

RP2

-24 -8.0 – G

Hysteresis B

hys

BOP – B

RP

5.0 19 35 G

Operate Differential B

OP(dif)

B

OP1

– B

OP2

– -2.0 ±30 G

Release Differential B

RP(dif)

B

RP1

– B

RP2

– -3.3 ±30 G

Symmetry B

sym

BOP + B

RP

––±30 G

NOTES:1. As used here, negative flux densities are defined as less than zero (algebraic convention) and -50 G is less than +10 G.

2. Typical Data is at TA = +25°C and VCC = 12 V and is for design information only.

3425

DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

4

TYPICAL OPERATING CHARACTERISTICS

as a function of temperature

TOTAL SUPPLY CURRENT

OUTPUT SATURATION VOLTAGE

CHANNEL 2 SWITCH POINTS

0 50 100

AMBIENT TEMPERATURE IN °C

-50

Dwg. GH-026-7

SWITCH POINT IN GAUSS

0

5

150-25 25 75 125

10

15

20

25

-25

-20

-15

-10

-5

RELEASE POINT

VCC = 18-26.5 V

V

CC

= 3.3-5 V

VCC = 5 V

V

CC

= 3.3 V

V

CC

= 18 V

V

CC

= 26.5 V

OPERATE POINT

0 50 100

AMBIENT TEMPERATURE IN °C

-50

Dwg. GH-026-8

SWITCH POINT IN GAUSS

0

5

OPERATE POINT

150-25 25 75 125

10

15

20

25

-25

-20

-15

-10

-5

RELEASE POINT

VCC = 26.5 V

V

CC = 18 V

V

CC = 3.3-5 V

VCC = 26.5 V

V

CC = 5 V

V

CC = 18 V

V

CC = 3.3 V

CHANNEL 1 SWITCH POINTS

0 25 50 75 100

300

0

AMBIENT TEMPERATURE IN °C

200

100

-50

Dwg. GH-029-5

SATURATION VOLTAGE IN mV

150-25 125

I

OUT

= 20 mA

VCC = 26.5 V

VCC = 3.3 V

0

SUPPLY CURRENT IN mA

8

6

4

2

0 255075100

AMBIENT TEMPERATURE IN °C

-50

Dwg. GH-028-8

125-25 150

B ≥ B

OP

VCC = 18 V

VCC = 18 V

VCC = 3.3 V

VCC = 3.3 V

B ≤ B

RP