These Hall-effect switches are monolithic integrated circuits with

tighter magnetic specifications, designed to operate continuously over
extended temperatures to +150

C, and are more stable with both tem-

perature and supply voltage changes. The unipolar switching character-
istic makes these devices ideal for use with a simple bar or rod magnet.
The three basic devices (A3121, A3122, and A3123) are identical except
for magnetic switch points.

Each device includes a voltage regulator for operation with supply

voltages of 4.5 volts to 24 volts, reverse battery protection diode, qua-
dratic Hall-voltage generator, temperature compensation circuitry, small-
signal amplifier, Schmitt trigger, and an open-collector output to sink up
to 25 mA. With suitable output pull up, they can be used with bipolar or
CMOS logic circuits. The A3121 is an improved replacement for the
UGx3113 and UGx3119.

The first character of the part number suffix determines the device

operating temperature range. Suffix `E' is for the automotive and
industrial temperature range of -40

C to +85

C. Suffix `L' is for the

automotive and military temperature range of -40

C to +150

C. Two

package styles provide a magnetically optimized package for most
applications. Suffix `LT' is a miniature SOT89/TO-243AA transistor
package for surface-mount applications; suffix `UA' is a three-lead
ultra-mini-SIP.

HALL-EFFECT SWITCHES

FOR HIGH-TEMPERATURE OPERATION

Always order by complete part number, e.g., A3121EUA .

ABSOLUTE MAXIMUM RATINGS

at T

= +25

Supply Voltage, V

........................... 30 V

Reverse Battery Voltage, V

RCC

........ -30 V

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

Output OFF Voltage, V

OUT

................ 28 V

Reverse Output Voltage, V

OUT

........ -0.5 V

Continuous Output Current, I

OUT

... 25 mA

Operating Temperature Range, T

Suffix `E' ................. -40

C to +85

Suffix `L' ............... -40

C to +150

Storage Temperature Range,

.............................. -65

C to +170

FEATURES and BENEFITS

s Superior Temp. Stability for Automotive or Industrial Applications
s 4.5 V to 24 V Operation ... Needs Only An Unregulated Supply
s Open-Collector 25 mA Output ... Compatible with Digital Logic
s Reverse Battery Protection
s Activate with Small, Commercially Available Permanent Magnets
s Solid-State Reliability ... No Moving Parts
s Small Size
s Resistant to Physical Stress

Data Sheet

27621.4C*

Pinning is shown viewed from branded side.

3121, 3122,

AND

3123

Dwg. PH-003A

SUPPLY

GROUND

OUTPUT

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION

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

FUNCTIONAL BLOCK DIAGRAM

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Supply Voltage

Operating

4.5

Output Saturation Voltage

OUT(SAT)

OUT

= 20 mA, B > B

14040

0 mV

Output Leakage Current

OFF

OUT

= 24 V, B < B

<1.010

Supply Current

B < B

(Output OFF)

4.6

9.0mA

Output Rise Time

= 820

, C

= 20 pF

0.04

2.0

Output Fall Time

= 820

, C

= 20 pF

0.18

2.0

ELECTRICAL CHARACTERISTICS over operating temperature range, at V

= 12 V.

MAGNETIC CHARACTERISTICS in gauss over operating supply voltage range.

Part Numbers*

A3121

A3122

A3123

Characteristic

Min.

Typ.

Max.

Min.

Typ.

Max.

Min.

Typ.

Max

at T

= 25

250350450

28034040

250345

440

over operating temp. range

22035050

260340430

230345

470

at T

= 25

125

245

380

140235

330

18024030

over operating temp. range

80245

410

120235

360

160240330

hys

at T

= 25

7010

140

7010

140

7010

140

over operating temp. range

6010

150

7010

140

7010

140

NOTES: Typical values are at T

= +25

C and V

= 12 V.

= operate point (output turns ON); B

= release point (output turns OFF); B

hys

= hysteresis (B

- B

*Complete part number includes a suffix to identify operating temperature range (E- or L-) and package type ( -LT or -UA).

REG.

Dwg. FH-005-2

GROUND

OUTPUT

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES

FOR HIGH-TEMPERATURE

OPERATION

www.allegromicro.com

SWITCH POINTS

OUTPUT SATURATION VOLTAGE

* Complete part number includes a suffix denoting operating temperature range (E- or L-) and package type ( -LT or -UA).

TYPICAL OPERATING CHARACTERISTICS

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-038

SWITCH POINT IN GAUSS

300

400

200

100

OPERATE POINT

RELEASE POINT

V = 12 V

150

-25

125

100

300

AMBIENT TEMPERATURE IN

°
°
°
°

200

100

-50

Dwg. GH-040

SATURATION VOLTAGE IN mV

150

-25

125

I = 20 mA

V = 4.524 V

OUT

100

AMBIENT TEMPERATURE IN

°
°
°
°

-50

Dwg. GH-039

125

-25

V = 12 V

SUPPLY CURRENT IN mA

7.0

6.0

5.0

4.0

150

SUPPLY VOLTAGE IN VOLTS

Dwg. GH-041

SUPPLY CURRENT IN mA

2.0

4.0

6.0

8.0

T = +25

SUPPLY CURRENT

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION

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

SENSOR LOCATIONS

(

0.005" [0.13 mm] die placement)

OPERATION

The output of these devices (pin 3) switches low when the mag-

netic field at the Hall sensor exceeds the operate point threshold (B

At this point, the output voltage is V

OUT(SAT)

. When the magnetic field

is reduced to below the release point threshold (B

), the device output

goes high. The difference in the magnetic operate and release points is
called the hysteresis (B

hys

) of the device. This built-in hysteresis allows

clean switching of the output even in the presence of external mechani-
cal vibration and electrical noise.

APPLICATIONS INFORMATION

Extensive applications information for Hall-effect sensors is

available in:
· Hall-Effect IC Applications Guide, Application Note 27701;
· Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and
Lead Forming, Application Note 27703.1;
· Soldering of Through-Hole Hall-Sensor Dervices, Application Note
27703; and
· Soldering of Surface-Mount Hall-Sensor Devices, Application Note
27703.2.
All are provided in Allegro Electronic Data Book, AMS-702. or at

www.allegromicro.com

CHANGE IN OPERATE POINT

Suffix "LT"

Suffix "UA"

0.043"
1.09 mm

Dwg. MH-008-2D

0.0305"
0.775 mm
NOM

ACTIVE AREA DEPTH

0.089"

2.26 mm

Dwg. MH-011-2D

0.0195"
0.50 mm
NOM

BRANDED
SURFACE

ACTIVE AREA DEPTH

0.082"

2.07 mm

0.055"

1.38 mm

SUPPLY VOLTAGE IN VOLTS

Dwg. GH-042

CHANGE IN OPERATE POINT IN GAUSS

-5.0

5.0

T = +25

Allegro

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES

FOR HIGH-TEMPERATURE

OPERATION

www.allegromicro.com

Dwg. MA-009-3A in

0.072
0.064

0.167
0.155

0.059

BSC

0.0189
0.0142

0.047
0.035

0.102
0.090

0.063
0.055

0.0173
0.0138

0.090
0.084

0.0221
0.0173

0.118

BSC

0.181
0.173

Dwg. MA-009-3A mm

4.60
4.40

1.83
1.62

4.25
3.94

1.50

BSC

0.48
0.36

1.20
0.89

2.60
2.29

1.60
1.40

0.44
0.35

2.29
2.13

0.56
0.44

3.00

BSC

PACKAGE DESIGNATOR `LT'

(SOT89/TO-243AA)

Dimensions in Inches

(for reference only)

Dimensions in Millimeters

(controlling dimensions)

NOTES: 1.

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

Supplied in bulk pack (500 pieces per bag) or add "TR" to part number for tape and reel.

Only low-temperature (

240

C) reflow-soldering techniques are recommended for SOT89 devices.

0.098

0.031

0.102

0.047

0.181

0.079

Dwg. MA-012-3 in

Pads 1, 2, 3, and A -- Standard SOT89 Layout
Pads 1, 2, 3, and B -- Low-Stress Version
Pads 1, 2, and 3 only -- Lowest Stress, But Not Self Aligning

0.028

TYP

0.031

TYP

2.5

0.8

2.6

1.2

4.6

2.0

Dwg. MA-012-3 mm

Pads 1, 2, 3, and A -- Standard SOT89 Layout
Pads 1, 2, 3, and B -- Low-Stress Version
Pads 1, 2, and 3 only -- Lowest Stress, But Not Self Aligning

0.7

TYP

0.8

TYP

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION

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

Dimensions in Inches

(controlling dimensions)

Dimensions in Millimeters

(for reference only)

PACKAGE DESIGNATOR `UA'

NOTES: 1.

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

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

Height does not include mold gate flash.

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

Where no tolerance is specified, dimension is nominal.

Supplied in bulk pack (500 pieces per bag).

Dwg. MH-014E in

0.164
0.159

0.062
0.058

0.0173
0.0138

0.050

BSC

0.640
0.600

0.0189
0.0142

0.085

MAX

0.031

0.122
0.117

SEE NOTE

Dwg. MH-014E mm

4.17
4.04

1.57
1.47

0.44
0.35

1.27

BSC

16.26
15.24

0.48
0.36

2.16

MAX

0.79

3.10
2.97

SEE NOTE

Radial Lead Form (order A312xxUA-LC)

NOTE:

Lead-form dimensions are the nominals produced on the
forming equipment. No dimensional tolerance is implied or
guaranteed for bulk packaging (500 pieces per bag).

0.620"
0.500"

(15.7 mm
12.7 mm)

0.100"

(2.5 mm)

Dwg. MH-026

0.108"

(2.74 mm)

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES

FOR HIGH-TEMPERATURE

OPERATION

www.allegromicro.com

HALL-EFFECT SENSORS

UNIPOLAR HALL-EFFECT DIGITAL SWITCHES

Partial

Operate

Release

Hysteresis

Replaces

Part

Point (G)

(G)

Oper.

and

Number

Over Oper. Voltage & Temp. Range

Temp.

Packages

Comments

A3121x

220 to 500

80 to 410

60 to 150

E, L

LT, UA

3019, 3113, 3119

A3122x

260 to 430

120 to 360

70 to 140

E, L

LT, UA

A3123x

230 to 470

160 to 330

70 to 140

E, L

LT, UA

A3141x

30 to 175

10 to 145

20 to 80

E, L

LT, UA

3040, 3140

A3142x

115 to 245

60 to 190

30 to 80

E, L

LT, UA

A3143x

205 to 355

150 to 300

30 to 80

E, L

LT, UA

A3144x

35 to 450

25 to 430

>20

E, L

LT, UA

3020, 3120

A3161E

<160 (Typ 130)

>30 (Typ 110)

5 to 80

LT, UA

2-wire operation

A3163E

<160 (Typ 98)

>30 (Typ 79)

5 to 40

LT, UA

2-wire

A3240x

<50 (Typ 35)

>5 (Typ 25)

Typ 10

E, L

LH, LT, UA

chopper stabilized

A3250x

<50 to >350

5 to 35

J, L

programmable, chopper stabilized

A3251x

<50 to >350

5 to 35

J, L

programmable, chopper stabilized

A3361E

<125

>405 to 30E

LH, LT, UA

2-wire, chopper stabilized,

output normally high

A3362E

<125

>405 to 30E

LH, LT, UA

2-wire, chopper stabilized,

output normally low

MICROPOWER OMNIPOLAR HALL-EFFECT DIGITAL SWITCHES

Partial

Operate

Release

Hysteresis

Average

Part

Points (G)

(G)

Oper.

Supply

Number

Over Oper. Voltage & Temp. Range

Temp.

Packages

Current (

A3209E

>-60, <60

<-5, >5

Typ 7.7

LH, UA

<425 (Typ 145)

A3210E

>-60, <60

<-5, >5

Typ 7.7

LH, UA

<60 (Typ 8.8)

A3212E

>-55, <55

<-10, >10

Typ. 8

LH, UA

<10 (Typ 4.2)

BIPOLAR HALL-EFFECT DIGITAL SWITCHES

Partial

Operate

Release

Hysteresis

Replaces

Part

Point (G)

(G)

Oper.

and

Number

Over Oper. Voltage & Temp. Range

Temp.

Packages

Comments

UGx3132

<95 (Typ 32)

>-95 (Typ -20) >30 (Typ 52)

K, L, S

LT, UA

3030, 3130, 3131

UGx3133

<75 (Typ 32)

>-75 (Typ -20) >30 (Typ 52)

K, L, S

LT, UA

UGx3134

-40 to 50

-50 to 40

5 to 55

E, L

LT, UA

A3260x

<30 (Typ 10)

>-30 (Typ -10)

Typ 20

E, L

LH, LT, UA

2 wire, chopper stabilized

Notes: 1) Typical data is at TA = +25

C and nominal operating voltage.

2) "x" = Operating Temperature Range [suffix letter or (prefix)]: S (UGN) = -20

C to +85

C, E = -40

C to +85

J = -40

C to +115

C, K (UGS) = -40

C to +125

C, L (UGL) = -40

C to +150

3121, 3122,

AND

3123

HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION

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

The products described herein are manufactured under one or more

of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283;
5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719;
5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents
pending.

Allegro MicroSystems, Inc. reserves the right to make, from time to

time, such departures from the detail specifications as may be required
to permit improvements in the performance, reliability, or
manufacturability of its products. Before placing an order, the user is
cautioned to verify that the information being relied upon is current.

Allegro products are not authorized for use as critical components

in life-support appliances, devices, or systems without express written
approval.

The information included herein is believed to be accurate and

reliable. However, Allegro MicroSystems, Inc. assumes no responsibil-
ity for its use; nor for any infringements of patents or other rights of
third parties that may result from its use.

Part Number A3121