Two-wire wheel-speed sensor IC with integrated capacitor

Industry-leading performance in a very small package

The new A1688 from Allegro MicroSystems Europe is a Hall-effect sensor IC that provides a user-friendly solution for true zero-speed digital ring magnet and gear tooth sensing in two-wire automotive applications such as ABS braking systems.

The new device offers industry-leading performance in areas such as pitch deviation accuracy, consistent supply current distribution (better than six-sigma), low jitter and enhanced EMC performance provided by an integrated capacitor which also reduces the requirement for external components.

The integrated circuit incorporates a dual-element Hall-effect sensor and signal processing circuitry that switches in response to differential magnetic signals created by magnetic encoders, or, when properly back-biased with a magnet, from ferromagnetic targets. A sophisticated digital circuit reduces magnet and system offsets, calibrates the gain for air-gap independent switch points, and provides true zero-speed operation.

Signal optimisation occurs at power-up through the combination of offset and gain adjustment, and is maintained throughout operation with the use of a running-mode calibration scheme which provides immunity from environmental effects such as micro-oscillations of the sensed target or sudden air-gap changes.

The regulated current output is configured for two-wire interface circuitry, and is ideally suited to obtaining speed information in wheel speed applications. The Hall element spacing is optimised for high-resolution small-diameter targets.

The A1688 is offered in the UB package, which integrates the IC and the high-temperature ceramic capacitor in a single overmoulded SIP package with an outside diameter of less than 6.5 mm and offers the additional benefit of wider lead spacing. The package is lead (Pb) free, with 100% matt-tin leadframe plating.

About Allegro
Allegro MicroSystems, LLC is a leader in developing, manufacturing and marketing high-performance semiconductors. Allegro's innovative solutions serve high-growth applications within the automotive market, with additional focus on office automation, industrial, and consumer/communications solutions. Allegro is headquartered in Worcester, Massachusetts (USA) with design, applications, and sales support centers located worldwide. Further information about Allegro can be found at www.allegromicro.com

Allegro MicroSystems Europe, headquartered in Chertsey, United Kingdom, is the European sales and marketing operation, and operates a network of representatives and distributors throughout Europe.  Allegro also has an engineering design centre in Edinburgh in Scotland and an application and marketing centre in Annecy in France.