Two-wire unipolar Hall-effect switch minimises external component count

October 06, 2015 // By Julien Happich
A new package option for the Allegro MicroSystems A115x family of two-wire unipolar Hall-effect switches eliminates the need for an external capacitor and the associated PCB, saving size, component count and assembly cost and significantly simplifying the design process.

The A115x family, comprising the A1152, A1153, A1156, and A1157 devices, are factory-trimmed to optimise magnetic switchpoint accuracy. The different devices are distinguished by the choice of magnetic switch-points, output current, output polarity, and package.

These devices are produced using the Allegro advanced BiCMOS wafer fabrication process, which uses a patented high-frequency 4-phase chopper-stabilisation technique. This technique achieves magnetic stability over the full operating temperature range, and eliminates offsets inherent in devices with a single Hall element that are exposed to harsh application environments.

The A115x sensors were developed for use in automotive and industrial applications that are safety-critical or involve long sensor wiring harnesses. Typical applications include seat track position sensing, seat-belt buckle presence, hood/trunk latching, and shift selector position sensing.

Two-wire switches are particularly advantageous in cost- and/or weight-sensitive applications because they require one less wire for operation than the more traditional open-collector output switches. In addition, the system offers diagnostic capabilities because there is always output current flowing in either of two narrow ranges. A current level not within these ranges indicates a fault condition.

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