Amp

Regulator

Program/Lock

Low-Pass

Filter

GND

VCC

GND

Programming

Logic

Package UA Only

Offset

Adjust

Clock/Logic

To all

subcircuits

0.01 uF

V+

Description

The A1185 and A1186 are ultrasensitive, two-wire, unipolar

programmed, after final packaging of the sensor and

placement into the application. This advanced feature allows

the optimization of the sensor switching performance, by

effectively accounting for variations caused by mounting

tolerances for the device and the target magnet.

This family of devices are produced on the Allegro

MicroSystems new DABIC5 BiCMOS wafer fabrication

process,whichimplementsapatented,high-frequency,chopper-

stabilization technique that achieves magnetic stability and

eliminates the offsets that are inherent in single-element devices

exposed to harsh application environments. Commonly found

in a number of automotive applications, the A1185 and A1186

devices are utilized to sense: seat track position, seat belt buckle

presence, hood/trunk latching, and shift selector position.

Two-wire unipolar switches are particularly advantageous

in price-sensitive applications, because they require one less

wire than the more traditional open-collector output switches.

A1185-DS, Rev. 2

Features and Benefits

▪ Chopper stabilization

▫ Low switchpoint drift over operating

temperature range

▫ Low sensitivity to stress

▪ Field programmable for optimized switchpoints

▪ On-chip protection

▫ Supply transient protection

▫ Reverse-battery protection

▫ On-board voltage regulator

▫ 3.5 to 24 V operation

Ultrasensitive Two-Wire Field-Programmable

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)

A1185 and A1186