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Allegro Announces Improvements to Family of Gear-Tooth
Sensor ICs
Improvements include integrated capacitor, smaller package size 
Worcester, MA, June 8, 2005 — Allegro MicroSystems, Inc. announces the release of the A1421LK, A1422LK, and A1423LK, improved additions to Allegro's family of AC-coupled Hall-effect gear-tooth sensor ICs. Improvements include a smaller package size and an integrated filter capacitor to provide additional reliability to the system solution.
The A1421LK, A1422LK, and A1423LK are AC-coupled Hall-effect gear-tooth sensor ICs with monolithic integrated circuits that switch in response to changing differential magnetic fields created by a moving ring magnet or by a ferrous target when back-biased with a magnet. These devices are ideal for use in speed, position and timing applications such as transmission and engine management. This family of devices also includes an integrated filter capacitor so a high-accuracy analog solution can be achieved without additional external components, thus improving reliability for the final sensing solution.
Two integrated Hall transducers sense changes in fields and are differentially amplified by on-chip electronics. Differential sensing provides immunity to radial vibration within the device's operating air gap range by rejection of the common mode signal change. Steady-state system offsets are eliminated using an on-chip differential band-pass filter. This filter also provides relative immunity to interference from electromagnetic sources. The device utilizes advanced temperature compensation for the high-pass filter, sensitivity, and Schmitt trigger switch-points to guarantee optimal operation to low frequencies over a wide range of air gaps and temperatures.
Each device includes a voltage regulator, two Hall-effect sensing elements, temperature-compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger, and an output driver that requires a pull-up resistor. The on-board regulator permits operation with supply voltages of 4.0 to 26.5 volts. The output stage can easily switch 20 mA over the full frequency response range of the sensor and is compatible with bipolar and MOS logic circuits.
The devices differ in their switchpoints: the A1421 provides one zero crossing, the A1422 includes narrow set and symmetric switchpoints, and the A1423 offers high vibration immunity with its wide set switchpoints. This variety of options gives the flexibility to achieve a solution for a wide variety of application needs, including transmission and crankshaft speed sensing.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power and Hall-effect sensor integrated circuits. Allegro's innovative solutions serve high-growth applications within the automotive, communications, computer/office automation, consumer and industrial markets. Allegro is headquartered in Worcester, Massachusetts (USA) with design and applications centers located in North and South America, Asia, and Europe. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director - Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com