A3280, A3281, and A3283

Chopper-Stabilized, Precision Hall-Effect Latches

Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.

Date of status change: January 31, 2011

Recommended Substitutions:

For existing customer transition, and for new customers or new appli-
cations, refer to the A1220, A1221, and A1223.

NOTE: For detailed information on purchasing options, contact your

local Allegro field applications engineer or sales representative.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
 A3280, A3281, and A3283
Chopper-Stabilized, Precision
Hall-Effect Latches

Features and Benefits Description

▪ Symmetrical switch points The A3280, A3281, and A3283 Hall-effect latches
▪ Resistant to physical stress are extremely temperature-stable and stress-resistant
▪ Superior temperature stability sensor ICs especially suited for operation over extended
▪ Output short-circuit protection temperature ranges to +150°C. Superior high-temperature
▪ Operation from unregulated supply performance is made possible through dynamic offset
▪ Reverse battery protection cancellation, which reduces the residual offset voltage
▪ Solid-state reliability normally caused by device overmolding, temperature
▪ Small size dependencies, and thermal stress. The three devices are
identical except for magnetic switch points.
Packages: Each device includes on a single silicon chip a voltage
regulator, Hall-voltage generator, small-signal amplifier,
chopper stabilization, Schmitt trigger, and a short-circuit
protected open-collector output to sink up to 25 mA.
A south pole of sufficient strength will turn the output
on. A north pole is necessary to turn the output off. An
Package LH on-board regulator permits operation with supply voltages
of 4.2 to 24 volts.
Three package styles provide a magnetically optimized
package for most applications. Package type LH is a
modified SOT23W surface-mount package, LT is a
miniature SOT89/TO-243AA transistor package for
Package LT Package UA surface-mount applications; while UA is a three-lead
ultra-mini-SIP for through-hole mounting. Each package
type is lead (Pb) free (suffix, –T), with 100% matte tin
leadframe plating.
Not to scale

Functional Block Diagram

27609.20-DS, Rev. M
A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

Selection Guide
BRP(MIN) BOP(MAX)
Ambient, TA
Part Number Packing* Mounting (TA = 25°C) (TA = 25°C)
(°C)
(G) (G)
A3283ELTTR-T 7-in. reel, 1000 pieces/reel SOT89 Surface Mount
–40 to 85
A3283EUA-T Bulk, 500 pieces/bag 3-pin SIP through hole
A3283LLHLT-T 7-in. reel, 3000 pieces/reel SOT23W Surface Mount –180 180
A3283LLTTR-T 7-in. reel, 1000 pieces/reel SOT89 Surface Mount –40 to 150
A3283LUA-T Bulk, 500 pieces/bag 3-pin SIP through hole
*Contact Allegro for additional packing options.

Absolute Maximum Ratings

Characteristic Symbol Notes Rating Units
Supply Voltage VCC 26.5 V
Reverse Battery Voltage VRCC –30 V
Magnetic Flux Density B Unlimited G
Output Off Voltage VOUT 26 V
Internal current limiting is intended to protect
Continuous Output Current IOUT 25 mA
the device from output short circuits.
Reverse Output Currrent IROUT –50 mA
Range E –40 to 85 ºC
Operating Ambient Temperature TA
Range L –40 to 150 ºC
Maximum Junction Temperature TJ(max) 165 ºC
Storage Temperature Tstg –65 to 170 ºC

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

X
PTCT

V
CC

1 2 3
GROUND
SUPPLY

OUTPUT

Dwg. PH-003-2

Suffix '–LT' & '–UA' Pinning Suffix ‘–LH’ Pinning

(SOT89/TO-243AA & ultra-mini SIP) (SOT23W)

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

ELECTRICAL CHARACTERISTICS over operating temperature range.

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Supply Voltage Range VCC Operating, TJ < 170°C1 4.2 – 24 V

Output Leakage Current IOFF VOUT = 24 V, B < BRP – – 10 μA

Output Saturation Voltage VOUT(SAT) IOUT = 20 mA, B > BOP – 185 500 mV

Output Current Limit IOM B > BOP 30 – 60 mA

Power-On Time tpo VCC > 4.2 V – – 50 μs

Chopping Frequency fC – 340 – kHz

Output Rise Time tr RL = 820 , CL = 20 pF – 0.2 2.0 μs

Output Fall Time tf RL = 820 , CL = 20 pF – 0.1 2.0 μs

Supply Current ICC B < BRP, VCC = 12 V – 3.0 8.0 mA

B > BOP, VCC = 12 V – 4.0 8.0 mA

Reverse Battery Current ICC VRCC = -30 V – – -5.0 mA

Zener Voltage VZ + VD ICC = 15 mA, TA = 25°C 28 32 37 V

Zener Impedance zz + zD ICC = 15 mA, TA = 25°C – 50 – 

NOTES: 1. Maximum voltage must be adjusted for power dissipation and junction 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 voltage range.

Part Numbers1

A3280 A3281 A3283

Characteristic Test Conditions Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. Units

Operate Point, BOP at TA = +25°C and TA = max. 5.0 22 40 15 50 90 100 150 180 G

at TA = -40°C 5.0 – 40 15 – 90 100 – 200 G

Release Point, BRP at TA = +25°C and TA = max. -40 -23 -5.0 -90 -50 -15 -180 -150 -100 G

at TA = -40°C -40 – -5.0 -90 – -15 -200 – -100 G

Hysteresis, Bhys at TA = +25°C and TA = max. 10 45 80 30 100 180 – 300 360 G

(BOP - BRP) at TA = -40°C – – 80 – – 180 – – 360 G

NOTES: 1. Complete part number includes a suffix to identify operating temperature range (E or L) and package type (LH, LT, or UA).
2. As used here, negative flux densities are defined as less than zero (algebraic convention) and -50 G is less than +10 G.
3. Typical Data is at TA = +25°C and VCC = 12 V and is for design information only.
4. 1 gauss (G) is exactly equal to 0.1 millitesla (mT).

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

TYPICAL OPERATING CHARACTERISTICS

as a function of temperature

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

TYPICAL OPERATING CHARACTERISTICS

as a function of temperature (cont'd)
OUTPUT SATURATION VOLTAGE SUPPLY CURRENT
300 6.0

IOUT = 20 mA
V CC = 12 V
V CC = 12 V
5.0

200

4.0
OUTPUT ON, B > B OP OP

100
3.0
OUTPUT OFF, B < BRP RP

0 2.0
-50 -25 0 25 50 75 100 125 150 -50 -25 0 25 50 75 100 125 150
AMBIENT TEMPERATURE IN °C AMBIENT TEMPERATURE IN °C
Dwg. GH-029-4 Dwg. GH-028-5

TYPICAL OPERATING CHARACTERISTICS

as a function of supply voltage
A3280* SWITCH POINTS A3281* SWITCH POINTS
40 80

OPERATE POINT
OPERATE POINT
20 40

T A = 150°C T A = 150°C
0 T A = -40°C 0 T A = -40°C

-20 RELEASE POINT -40

RELEASE POINT

-40 -80
3.0 3.5 4.0 4.5 5.0 24 3.0 3.5 4.0 4.5 5.0 24
SUPPLY VOLTAGE IN VOLTS SUPPLY VOLTAGE IN VOLTS
Dwg. GH-021-3 Dwg. GH-021-1

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

TYPICAL OPERATING CHARACTERISTICS

as a function of supply voltage (cont’d)

OUTPUT SATURATION VOLTAGE

250
IOUT = 20 mA
T A = 150°C
T A = +25°C
T A = -40°C

225

200

175

150
3.0 3.5 4.0 4.5 5.0 24
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-055-1

SUPPLY CURRENT
8.0
OUTPUT ON
T A = 150°C
7.0 T A = +25°C
T A = -40°C

6.0

5.0

4.0

3.0

2.0

1.0

0
3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 11 12
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-058-4

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

FUNCTIONAL DESCRIPTION
Chopper-Stabilized Technique. The Hall element can be
considered as a resistor array similar to a Wheatstone bridge. A
large portion of the offset is a result of the mismatching of these
resistors. These devices use a proprietary dynamic offset cancel-
lation technique, with an internal high-frequency clock to reduce
the residual offset voltage of the Hall element that is normally
caused by device overmolding, temperature dependencies, and
thermal stress. The chopper-stabilizing technique cancels the
mismatching of the resistor circuit by changing the direction of
the current flowing through the Hall plate using CMOS switches
and Hall voltage measurement taps, while maintaing the Hall-
voltage signal that is induced by the external magnetic flux. The
signal is then captured by a sample-and-hold circuit and further
processed using low-offset bipolar circuitry. This technique
produces devices that have an extremely stable quiescent Hall
output voltage, are immune to thermal stress, and have precise
recoverability after temperature cycling. This technique will
also slightly degrade the device output repeatability. A relatively
high sampling frequency is used in order that faster signals can
be processed.
More detailed descriptions of the circuit operation can be
found in: Technical Paper STP 97-10, Monolithic Magnetic Hall
Sensing Using Dynamic Quadrature Offset Cancellation and
Technical Paper STP 99-1, Chopper-Stabilized Amplifiers With A
Track-and-Hold Signal Demodulator.
Operation. The output of these devices switches low (turns
on) when a magnetic field perpendicular to the Hall element
exceeds the operate point threshold (BOP). After turn-on, the
output is capable of sinking 25 mA and the output voltage is
VOUT(SAT). Note that the device latches; that is, a south pole of
sufficient strength towards the branded surface of the device
will turn the device on; removal of the south pole will leave the
device on. When the magnetic field is reduced below the release
point (BRP), the device output goes high (turns off). The differ-
ence in the magnetic operate and release points is the hysteresis
(Bhys) of the device. This built-in hysteresis allows clean switch-
ing of the output even in the presence of external mechanical
vibration and electrical noise.
Powering up in the absence of a magnetic field (less than
BOP and higher than BRP) will allow an indeterminate output
state. The correct state is warranted after the first excursion
beyond BOP or BRP.
It is strongly recommended that an external bypass capacitor

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

APPLICATIONS INFORMATION
be connected (in close proximity to the Hall element) between the vices, Application Note 27703.1
supply and ground of the device to reduce both external noise and More detailed descriptions of the chopper-stabilized circuit opera-
noise generated by the chopper-stabilization technique. tion can be found in:
The simplest form of magnet that will operate these devices is • Monolithic Magnetic Hall Sensing Using Dynamic Quadrature
a ring magnet. Other methods of operation, such as linear mag- Offset Cancelation, Technical Paper STP 97-10; and
nets, are possible. • Chopper-Stabilized Amplifiers With A Track-and-Hold Signal
Extensive applications information for Hall-effect devices is Demodulator, Technical Paper STP 99-1.
available in: All are provided at
• Hall-Effect IC Applications Guide, Application Note 27701; www.allegromicro.com
• Guidelines for Designing Subassemblies Using Hall-Effect De-

SUPPLY
3

OUTPUT
PTCT

0.1 MF
CC

X
1

SUPPLY
V

Dwg. EH-013

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

Package LH, 3-Pin (SOT-23W)

+0.12
2.98 –0.08

1.49 D
4°±4°
3 A
+0.020
0.180–0.053

0.96 D

+0.10 +0.19 2.40

2.90 –0.20 1.91 –0.06
0.70
D
0.25 MIN

1.00

1 2

0.55 REF 0.25 BSC 0.95

Seating Plane
Gauge Plane B PCB Layout Reference View

8X 10° REF Branded Face

1.00 ±0.13
NNT

+0.10 1
0.05 –0.05
0.95 BSC C Standard Branding Reference View
0.40 ±0.10
N = Last two digits of device part number
T = Temperature code
For Reference Only; not for tooling use (reference dwg. 802840)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Active Area Depth, 0.28 mm REF
B Reference land pattern layout
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances
C Branding scale and appearance at supplier discretion

D Hall element, not to scale

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

Package LT, 3-Pin SOT89

4.50±0.10
+0.10
1.73 –0.11
2.50
A 2.00
2.24
0.80

1.14 2.60 4.60

+0.15 +0.09
+0.15 2.45 –0.16 2.20 –0.07 Parting
4.10 –0.16 Line

+0.20
1.00 –0.11
1.00
1 2 3 +0.04
0.40 –0.05
0.70 1.50
1.50±0.10 B PCB Layout Reference View
Basic pads for low-stress, not self-aligning
Additional pad for low-stress, self-aligning
0.42±0.06 Additional area for IPC reference layout
0.50±0.06

2X 1.50 BSC

For Reference Only; not for tooling use (reference JEDEC. TO-243AA)
Dimensions in millimeters NNT
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Active Area Depth, 0.78 mm REF 1
B Reference land pattern layout (reference IPC7351 SOT89N); C Standard Branding Reference View
All pads a minimum of 0.20 mm from all adjacent pads; = Supplier emblem
adjust as necessary to meet application process N = Last two digits of device part number
requirements and PCB layout tolerances T = Temperature code
C Branding scale and appearance at supplier discretion
D Hall element, not to scale

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A3280, A3281 Chopper-Stabilized, Precision
and A3283 Hall-Effect Latches

Package UA, 3-Pin SIP

+0.08
4.09 –0.05

45°
B
C
E
2.06
1.52 ±0.05

1.45 E
Mold Ejector
+0.08 Pin Indent NNT
3.02 –0.05
E
Branded 45°
Face 1
2.16 D Standard Branding Reference View
MAX
= Supplier emblem
0.79 REF N = Last two digits of device part number
A T = Temperature code
0.51
REF
1 2 3

For Reference Only; not for tooling use (reference DWG-9049)

Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
+0.03 Exact case and lead configuration at supplier discretion within limits shown
0.41 –0.06
15.75 ±0.51

A Dambar removal protrusion (6X)

B Gate burr area
C Active Area Depth, 0.50 mm REF
D Branding scale and appearance at supplier discretion
E Hall element, not to scale

+0.05 1.27 NOM

0.43 –0.07

Copyright ©2002-2010, Allegro MicroSystems, Inc.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to per-
mit 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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use;
nor for any infringement of patents or other rights of third parties which may result from its use.

For the latest version of this document, visit our website:

www.allegromicro.com
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