New package for two-wire unipolar Hall-effect sensors cuts costs

Paul Boughton

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, writes Nick Flaherty.

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 Allegro’s 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. The two-wire switches have cost and weight advantages because they require one less wire for operation than the more traditional open-collector output switches. The system also 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.

All A115x family members are offered in three package styles. The LH is a SOT-23W style miniature low-profile package for surface-mount applications. The UA is a 3-pin ultra-miniature single inline package for through-hole mounting. The UB is a 2-pin ultra-miniature single inline package with an integrated capacitor for through-hole mounting or for welding directly to connector pins, eliminating the PCB entirely. All three packages are RoHS-compliant, with 100% matt tin leadframe plating.