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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 IC 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 IC 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 IC 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.
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