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High-Performance Power ICs and Hall-Effect Sensors
Allegro Announces a New High-Accuracy Speed Sensor
with Integrated Tracking Capacitor
Excellent Timing Accuracy and Repeatability 
Worcester, MA — June 18, 2004 — Allegro MicroSystems, Inc. announces a new high-accuracy analog speed sensor with integrated tracking capacitor and dual zero-crossing output signal. Allegro's A1425 is ideal for automotive crankshaft speed sensing applications using ring magnets. This ac-coupled differential sensor with on-chip capacitor is a true zero-crossing detector; the output switches precisely when the difference in magnetic field strength between the two Hall elements is zero. A unique dual-comparator scheme provides for accurate switching at the zero crossing on both the positive and negative going regions of the differential signal, while utilizing hysteresis to prevent false switching. These accurate switch-points are maintained over the entire automotive temperature range by an on-chip temperature compensation circuit.
When coupled with a back-biasing magnet, the sensor can be configured to turn on or off with the leading or trailing edge of a gear-tooth or slot. Two integrated Hall transducers sense changes in fields on the magnet face caused by a moving ferrous mass and are differentially amplified by on-chip electronics.
This differential sensing design provides immunity to radial vibration within the device's operating air gap. Steady-state magnet and system offsets are eliminated using an on-chip differential bandpass filter. This filter also provides relative immunity to interference from electromagnetic sources. The on-chip temperature compensation and Schmitt trigger, guarantees optimal operation to low frequencies over a wide range of air gaps and temperatures.
Allegro MicroSystems, Inc. is a supplier of advanced mixed-signal power semiconductors and Hall-effect sensors targeted toward the automotive, communications, computer/office automation, consumer and industrial markets. It maintains a leadership position in the integrated magnetic sensor and integrated motor driver product segments. With over 2,000 employees, Allegro is headquartered in Worcester, MA. Further information about Allegro, including free samples of our products, can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director – Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com