A1145 and A1146

A1145-DS, Rev. 6

Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

ABSOLUTE MAXIMUM RATINGS

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

Operating Temperature

On-chip protection

Supply transient protection

Reverse-battery protection

On-board voltage regulator

3.5 to 24 V operation

Ultrasensitive Two-Wire Chopper-Stabilized

Unipolar Hall Effect Switches

Package LH, 3-pin SOT

Features and Benefits

The A1145 and A1146 devices are two-wire, unipolar, Hall effect switches that are

factory-programmed at end-of-line to optimize ultrasensitive magnetic switchpoint

accuracy. These devices use a patented high frequency chopper-stabilization tech-

nique, 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 latch-

ing, and shift selector position. Two-wire unipolar switches, such as the A1145

and A1146, 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 diagnos-

tics 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 con-

dition. These devices also feature on-chip transient protection and a Zener clamp

to protect against overvoltage conditions on the supply line.

The output currents of the A1146 switches HIGH in the presence of a south (+)

polarity magnetic field of sufficient strength, and switches LOW otherwise, as in

the presence of a weak field or a north (–) polarity field. The A1145 has an oppo-

site output: the currents switch LOW in the presence of a south-polarity magnetic

field of sufficient strength, and switch HIGH otherwise.

Both versions are offered in two package styles. The LH is a SOT-23W, miniature

low-profile package for surface-mount applications. The UA is a three-lead ultra-

mini SIP for through-hole mounting. Each package is available in a lead (Pb) free

version (suffix, –T) with 100% matte tin plated leadframe. Field-programmable

versions also available: A1185 and A1186.

Package UA, 3-pin SIP

Chopper stabilization

Low switchpoint drift over operating

temperature range

Low sensitivity to stress

Factory programmed at end-of-line for

optimized switchpoints

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