Hall-effect speed/direction sensor IC with hysteresis detection

February 11, 2015 // By Graham Prophet
A1232 from Allegro MicroSystems Europe is a Hall-effect speed and direction sensor IC with built-in hysteresis detection; it offers improved overall accuracy when sensing high-resolution, multi-pole ring magnets.

The IC is a sensitive temperature-stable magnetic sensing device for use in ring magnet based speed and direction sensing systems in harsh automotive and industrial environments. Allegro says it is the first device of its kind with the ability to detect when it powers up in the magnetic hysteresis band. This feature reduces angle accuracy error, which can occur when edges are missed at start-up.

The Allegro A1232 includes dual Hall elements spaced 1.63 mm apart that are photolithographically aligned to within 1 µm. The precise spacing of the sensing elements eliminates a major manufacturing hurdle encountered when using fine-pitch ring magnets. The signals from the dual Hall elements are encoded into logic outputs representing the speed and direction of the target.

Factory trimming and Allegro’s chopper stabilisation and dynamic offset cancellation techniques provide precise, symmetrical magnetic switchpoints over a wide range of operating conditions. A built-in voltage regulator, short-circuit protected outputs, internal Zener clamps, reverse battery protection, and a -40̊ to +150̊C operating range give the A1232 the ruggedness demanded by automotive applications. It occupies an 8-pin TSSOP (suffix LE) surface mount package.

The sensor IC is targeted at motor applications in the automotive market. Key applications include window lifts, sunroofs, sliding doors and tail/trunk lift gates. It is also suitable for non-automotive applications such as garage door openers and window blinds.

Allegro MicroSystems; www.allegromicro.com