Description

The A1140, A1141, A1142, and A1143 devices are sensitive,

two-wire, unipolar, Hall effect switches that are factory-

programmed at end-of-line to optimize magnetic switchpoint

accuracy.These devices use a patented high frequency chopper-

stabilization technique, produced using the Allegro advanced

BiCMOS wafer fabrication process, to achieve magnetic

stability and to eliminate offset inherent in single-element

devices exposed to harsh application environments.

Commonly found in a number of automotive applications,

these switches are utilized to sense seat track position,

seat belt buckle presence, hood/trunk latching, and shift

selector position. Two-wire unipolar switches, such as the

A1140/41/42/43 family, are particularly advantageous in

price-sensitive applications because they require one less

wire for operation than do switches with the more traditional

open-collector output. Additionally, the system designer

inherently gains diagnostics because there is always output

current flowing, which should be in either of two narrow

ranges. Any current level not within these ranges indicates a

fault condition. The A1140/41/42/43 family of switches also

A1140-DS, Rev. 8

Features and Benefits

▪ Chopper stabilization

▫ Low switchpoint drift over operating

temperature range

▫ Low sensitivity to stress

▪ Factory programmed at end-of-line for optimized

switchpoints

▪ On-chip protection

▫ Supply transient protection

▫ Reverse-battery protection

▫ On-board voltage regulator

▫ 3.5 to 24 V operation

Sensitive Two-Wire Chopper-Stabilized

Unipolar Hall Effect Switches

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Functional Block Diagram

Not to scale

Packages: 3 pin SOT23W (suffix LH), and

3 pin SIP (suffix UA)

A1140, A1141, A1142, and A1143

Amp

Regulator

Low-Pass

Filter

GND

VCC

GND

Package UA Only

0.01 uF

V+

Clock/Logic

To All Subcircuits