The

A3421xKA

is a

DISCONTINUED PRODUCT

Replaced by the

A3422xKA;

see later data sheet.

The A3421xKA and A3422xKA Hall-effect, direction-detection

sensors are a new generation of special-function integrated sensors that
are capable of sensing the direction of rotation of a ring magnet. These
transducers provide separate digital outputs that provide information on
magnet rotation speed, direction, and magnet pole count. These devices
eliminate the major manufacturing hurdles encountered in fine-pitch
direction-detection applications, namely maintaining accurate mechani-
cal location between the two active Hall elements. Here, the two Hall
elements are photolithographically aligned to better than 1

m, as

contrasted with 100

m or worse mechanical location tolerance when

manufactured discretely. These highly sensitive, temperature-stable,
magnetic transducers are ideal for use in digital-encoder systems in the
harsh environments of automotive or industrial applications. The
A3421xKA is a high-hysteresis device designed for low-resolution
pulse counting while the A3422xKA is a high-sensitivity device
optimized for use with high-density magnets.

The A3421xKA and A3422xKA monolithic integrated circuits

contain two independent Hall-effect latches whose digital outputs are
internally coupled to CMOS logic circuitry that decodes signal speed
and direction. Extremely low-drift BiCMOS circuitry is used for the
amplifiers to ensure symmetry between the two latches so that signal
quadrature can be maintained. An on-chip voltage regulator allows the
use of these devices from a 4.5 V to 18 V supply. Both devices have
standard open-collector outputs; the logic operation of both devices is
the same.

Two operating temperature ranges are provided; suffix `E' is for

the automotive and industrial temperature range of -40

C to +85

suffix `L' is for the automotive and military temperature range of
-40

C to +150

C. The 5-pin `KA' SIP package provides a cost-

competitive solution to linear magnetic sensing in harsh environments.

FEATURES

Internal Direction-Decoding Circuitry

Two Matched Hall Latches On A Single Substrate

Superior Temperature Stability

4.5 V to 18 V Operation
Electrically Defined Power-On State
Under-Voltage Lockout

HALL-EFFECT,

DIRECTION-DETECTION SENSORS

Always order by complete part number, e.g., A3421EKA .

Dwg. PH-015

SUPPLY

DIRECTION

GROUND

E1 OUTPUT

SPEED

LOGIC

Pinning is shown viewed from branded side.

ABSOLUTE MAXIMUM RATINGS

Supply Voltage, V

. . . . . . . . . . . . . 18 V

Magnetic Flux Density, B . . . . Unlimited

Output OFF Voltage, V

OUT

. . . . . . . . V

Output Sink Current, I

OUT

. . . . . . . 30 mA

Package Power Dissipation,

. . . . . . . . . . . . . . . . . . . . . . 500 mW

Operating Temperature Range, T

Suffix `EKA' . . . . . . . -40°C to +85°C

Suffix `LKA' . . . . . . -40°C to +150°C

Storage Temperature Range,

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

3421

AND

3422

PRELIMINARY INFORMATION

(subject to change without notice)

September 6, 2000

Data Sheet

27650.1

3421

AND

3422

HALL-EFFECT,

DIRECTION-DETECTION

SENSORS

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Supply Voltage Range

Operating, T

< 165

4.5

Output Leakage Current

OFF

OUT

= V

= 18 V

<1.0

Output Saturation Voltage

OUT(SAT)

OUT

= 20 mA

0.21

0.50

Power-On State

POS

= 0

5 V,

OFF

RP1

< B < B

OP1

, B

RP2

< B < B

OP2

Under-Voltage Lockout

CC(UV)

OUT

= 20 mA, V

= 0

5 V

3.5

Under-Voltage Hysteresis

CC(hys)

Lockout (V

CC(UV)

) - Shutdown

0.5

Power-On Time

> 4.5 V

Output Rise Time

= 20 pF, R

= 820

200

Output Fall Time

= 20 pF, R

= 820

200

Direction Change Delay

= 20 pF, R

= 820

0.5

1.0

5.0

Supply Current

= 8 V, All outputs OFF

5.0

9.0

ELECTRICAL CHARACTERISTICS over operating temperature range.

100

125

175

0.5

0.1

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

TEMPERATURE IN

°
°
°
°

0.4

0.3

0.2

Dwg. GH-069

= 164

C/W

0.6

150

NOTES: 1. Maximum supply voltage must be adjusted for power dissipation and ambient temperature.

2. Typical Data is at V

= 12 V and T

= +25

C and is for design information only.

3421

AND

3422

HALL-EFFECT,
DIRECTION-DETECTION
SENSORS

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

A3421xKA

A3422xKA

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Min.

Typ.

Max.

Units

Operate Point

= -40

140

185

300

= +25

130

160

280

= Maximum

120

260

Release Point

= -40

-300

-190

-140

-85

-19

= +25

-280

-175

-130

-75

-18

= Maximum

-260

-120

-75

-16

Hysteresis

hys

= -40

280

375

= +25

260

335

= Maximum

240

Operate Differential

OP1

- B

OP2

Release Differential

RP1

- B

RP2

MAGNETIC CHARACTERISTICS over operating voltage range.

NOTES: 1. Magnetic flux density is measured at most sensitive area of device,

nominally located 0.014" (0.37 mm) below the branded face of the package.

2. Typical Data is at V

= 12 V and T

= +25

C and is for design information only.

3. As used here, negative flux densities are defined as less than zero (algebraic convention).

3421

AND

3422

HALL-EFFECT,

DIRECTION-DETECTION

SENSORS

TYPICAL A3421xKA CHARACTERISTICS

TYPICAL A3422xKA CHARACTERISTICS

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-026-1

SWITCH POINTS IN GAUSS

OPERATE POINT

RELEASE POINT

150

-25

125

-50

-40

-30

-20

-10

V = 8 V

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-051-1

125

-25

HYSTERESIS IN GAUSS

150

100

V = 8 V

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-026-2

SWITCH POINTS IN GAUSS

OPERATE POINT

RELEASE POINT

150

-25

125

100

150

200

250

-250

-200

-150

-100

-50

V = 8 V

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-051-2

125

-25

HYSTERESIS IN GAUSS

100

150

400

500

300

200

V = 8 V

3421

AND

3422

HALL-EFFECT,
DIRECTION-DETECTION
SENSORS

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

TYPICAL ELECTRICAL CHARACTERISTICS

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-053-1

125

-25

SUPPLY CURRENT IN mA

9.0

8.0

7.0

6.0

150

V = 8 V

ALL OUTPUTS ON

ALL OUTPUTS OFF

100

300

AMBIENT TEMPERATURE IN

°
°
°
°

200

100

-50

Dwg. GH-029-2

SATURATION VOLTAGE IN mV

150

-25

125

I = 20 mA

OUT

250

150

SUPPLY VOLTAGE IN VOLTS

8.0

6.0

Dwg. GH-058-3

SUPPLY CURRENT IN mA

9.0

7.0

5.0

ALL OUTPUTS ON

ALL OUTPUTS OFF

2.0

6.0

T = 25

3421

AND

3422

HALL-EFFECT,

DIRECTION-DETECTION

SENSORS

Outputs. The device provides three saturated outputs:
DIRECTION, E1 OUTPUT, and SPEED. DIRECTION
provides the direction output of the sensor and is defined
as OFF (high) for the direction E1 to E2 and ON (low) for
the direction E2 to E1. SPEED provides an XOR'd output
of the two sensors. Because of internal delays, DIREC-
TION will always be updated before SPEED and is
updated at every transition of E1 OUTPUT and E2 OUT-
PUT (internal) allowing the use of up-down counters
without the loss of pulses.

Power-On State. At power on, the logic circutry is reset
to provide an OFF (high) at DIRECTION and an OFF
(high) for E1 and E2 (internal) for magnetic fields less
than B

. This eliminates ambiguity when the device is

powered up and either sensor detects a field between B

and B

. If either sensor is subjected to a field greater than

, the internal logic will set accordingly.

The integrated circuit contains an internal voltage regula-
tor that powers the Hall sensors and both the analog and
digital circuitry. This regulator allows operation over a
wide supply voltage range and provides some immunity to
supply noise. The device also contains CMOS logic
circuitry that decodes the direction of rotation of the ring
magnet.

Quadrature/Direction Detection. Internal logic
circuitry provides outputs representing speed and direction
of the magnetic field across the face of the package. For
the direction signal to be appropriately updated, a quadra-
ture relationship must be maintained between the ring
magnet pole width*, the sensor-to-sensor spacing, and, to a
lesser extent, the magnetic switch points. For optimal
design, the sensor should be actuated with a ring magnet
pole width* two times the sensor-to-sensor spacing. This
will produce a sinusoidal magnetic field whose period
(denoted as

) is then four times the sensor-to-sensor

spacing. A quadrature relationship can also be maintained
for a ring magnet that has a period that satisfies the rela-
tionship n

/4 = 1.5 mm, where n is any odd integer.

Therefore, ring magnets with pole-pair spacings equal to 6
mm (n = 1), 2 mm (n = 3), 1.2 mm (n = 5), etc. are permit-
ted.

The response of the device to the magnetic field

produced by a rotating ring magnet is shown on page 2.
Note the phase shift between the two integrated sensors.

*"Pole" refers to a single pole (North or South) unless

stated as "pole pair" (North and South).

FUNCTIONAL DESCRIPTION

3421

AND

3422

HALL-EFFECT,
DIRECTION-DETECTION
SENSORS

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

APPLICATIONS INFORMATION

Operation with Fine-Pitch Ring Magnets. For
targets with a circular pitch of less than 4mm, a perfor-
mance improvement can be observed by rotating the front
face of the sensor subassembly (see below). This sensor
rotation decreases the effective sensor-to-sensor spacing,
provided that the Hall elements are not rotated beyond the
width of the target.

Applications. It is strongly recommended that an
external 0.01

F bypass capacitor be connected (in close

proximity to the Hall sensor) between the supply and
ground of the device to reduce both external noise and
noise generated by the internal logic.

The simplest form of magnet that will operate these

devices is a ring magnet. Other methods of operation,
such as linear magnets, are possible. Extensive applica-
tions information on magnets and Hall-effect sensors is
also available in the "Hsall-Effect IC Applications Guide"
which can be found in the latest issue of the Allegro
MicroSystems Electronic Data Book, AMS-702 or Appli-
cation Note 27701, or at

www.allegromicro.com

Dwg. MH-024

TARGET FACE WIDTH, F

>1.50 SIN

(mm)

>0.059 SIN

(inch)

1.50 COS

(mm)

0.059 COS

(inch)

0.059"

1.50 mm

Rotated sensor for
fine-pitch ring
magnets

3421

AND

3422

HALL-EFFECT,

DIRECTION-DETECTION

SENSORS

CRITERIA FOR DEVICE QUALIFICATION

All Allegro sensors are subjected to stringent qualification requirements prior to being released to production. To

become qualified, except for the destructive ESD tests, no failures are permitted.

Test Method and

Samples

Qualification Test

Test Conditions

Test Length

Per Lot

Comments

Temperature Humidity

JESD22-A101,

1000 hrs

Device biased for

Bias Life

= 85

C, RH = 85%

minimum power

Bias Life

JESD22-A108,

1000 hrs

= 150

C, T

= 165

(Surge Operating Life)

JESD22-A108,

1000 hrs

= 175

C, T

= 190

Autoclave, Unbiased

JESD22-A102,

96 hrs

= 121

C, 15 psig

High-Temperature

JESD22-A103,

1000 hrs

(Bake) Storage Life

= 170

Temperature Cycle

JESD22-A104

1000 cycles

-55

C to +150

ESD,

CDF-AEC-Q100-002

Pre/Post

3 per

Test to failure

Human Body Model

Reading

test

All leads > 8 kV

SENSOR LOCATIONS

(

0.005" [0.13 mm] die placement)

Dwg. MH-007-1

0.014"
0.37 mm
NOM

BRANDED
SURFACE

ACTIVE AREA DEPTH

0.059"

1.50 mm

0.096"

2.44 mm

0.072"

1.83 mm

3421

AND

3422

HALL-EFFECT,
DIRECTION-DETECTION
SENSORS

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

PACKAGE DESIGNATOR 'KA'

Dimensions in Inches

(controlling dimensions)

Dimensions in Millimeters

(for reference only)

Dwg. MH-010G in

0.018

0.015

0.016

0.050

BSC

0.063
0.059

0.600
0.560

0.083

MAX

0.252
0.247

0.181
0.176

SEE NOTE

SURFACE-MOUNT LEAD FORM (Suffix '-TL')

2.41

0.13

0.51

MIN

FLAT

Dwg. MH-015 mm

0.10

MAX

0.051

MAX

0.095

0.005

0.020

MIN

FLAT

Dwg. MH-015 in

0.004

MAX

0.002

MAX

NOTES: 1. Tolerances on package height and width represent allowable mold offsets. Dimensions given are measured at the widest point (parting line).

2. Exact body and lead configuration at vendor's option within limits shown.

3. Height does not include mold gate flash.

4. Recommended minimum PWB hole diameter to clear transition area is 0.035" (0.89 mm).

5. Where no tolerance is specified, dimension is nominal.

Dwg. MH-010G mm

0.46

0.38

0.41

1.27

BSC

1.60
1.50

15.24
14.23

2.11

MAX

6.40
6.27

4.60
4.47

SEE NOTE

3421

AND

3422

HALL-EFFECT,

DIRECTION-DETECTION

SENSORS

HALL-EFFECT SENSORS SELECTION GUIDE

Partial Part

Avail. Oper.

Operate Limits Over Temp.

Number

Temp.

BOP max

BRP min

Bhys min

Function

Notes

3046

E/L+200

-200

Gear-Tooth Sensor

3054

K/S

+300

5.0

Unipolar Multiplex

3056

E/L+225

-225

Gear-Tooth Sensor

3058

E/L+300

-300

150

Gear-Tooth Sensor

3059

K/S

+100

-100

AC Gear-Tooth Sensor

3060

K/S

+35

-35

AC Gear-Tooth Sensor

3121

E/L+500

+80

Unipolar Switch

3122

E/L+430

+120

Unipolar Switch

3123

E/L+470

+160

Unipolar Switch

3132

K/L/S

+95

-95

Bipolar Switch

3133

K/L/S

+75

-75

Bipolar Switch

3134

E/L+50

-50

5.0

Bipolar Switch

3141

E/L+175

+10

Unipolar Switch

3142

E/L+245

+60

Unipolar Switch

3143

E/L+355

+150

Unipolar Switch

3144

E/L+450

+25

Unipolar Switch

3161

+160

+30

5.0

2-Wire Unipolar Switch

3175

+180

-180

Latch

3177

+150

-150

Latch

3185

E/K/L/S

+300

-300

280

Latch

3187

E/K/L/S

+175

-175

100

Latch

3188

E/K/L/S

+200

-200

160

Latch

3189

E/K/L/S

+250

-250

100

Latch

3195

E/L+200

-200

110

atch

2, 3

3197

L+200

-200

110

atch

3210

7.7*

Chopper-Stabilized Switch

3235

+200

+15

Unipolar Switch

-15

-200

Unipolar Switch

3275

+250

-250

100

Latch

3421

E/L+300

-300

240

Direction Detection

3422

E/L+85

-85

Direction Detection

3503

Typ. 1.3 mV/G

Linear Sensor

3515

E/L Typ. 5.0 mV/G

Chopper-Stabilized L

inear Sensor

3516

E/L Typ. 2.5 mV/G

Chopper-Stabilized L

inear Sensor

3517

L/S

Typ. 5.0 mV/G

Chopper-Stabilized Linear Sensor

3518

L/S

Typ. 2.5 mV/G

Chopper-Stabilized Linear Sensor

3625

+150

-150

200*

900 mA Latch

3, 5, 6

3626

+150

-150

200*

400 mA Latch

3, 5, 6

5140

+240

+25

300 mA Unipolar Switch

3, 6

Operating Temperature Ranges:

C = 0

C to +70

C, S = -20

C to +85

C, E = -40

C to +85

C, K = -40

C to +125

C, L = -40

C to +150

Notes

1.Multiplexed two-wire sensor; after proper address, power/signal bus current indicates magnetic field condition.
2.Active pull down.
3.Protected.
4.Output 1 switches on south pole, output 2 switches on north pole for 2-phase, bifilar-wound, unipolar-driven brushless dc motor control.
5.Complementary outputs for 2-phase bifilar-wound, unipolar-driven brushless dc motor control.
6.Power driver output.
* Typical.
Latches will not switch on removal of magnetic field; bipolar switches may switch on removal of field but require field reversal for reliable operation over
operating temperature range.

Part Number A3421