Sensor detects tiny, symmetrical gear-tooth geometries.

Press Release Summary:

Model ATS645 differential sensor is offered with 2-wire back-biased package, peak detecting algorithms, and automatic gain control. Digital detection of gear tooth edges provides true zero-speed, gear-tooth sensing. Product consists of single-shot molded plastic package containing single chip differential Halt-effect sensor IC, Samarium Cobalt magnet, and flat ferrous pole piece. Hall elements, spaced 1.5 mm apart, allow device to sense small gear teeth geometries.

Original Press Release:

Next Generation Two-Wire Gear Tooth Sensor

Able to Sense Tiny Symmetrical Tooth Geometries with High Reliability

Worcester, MA, February 28, 2003 - Allegro MicroSystems, Inc. introduces the next generation differential digital gear tooth sensor with a two-wire back-biased package, peak detecting algorithms and automatic gain control. The ATS645 provides a user-friendly solution for true zero-speed gear tooth sensing in two wire applications by providing digital detection of gear tooth edges. The ATS645 is a highly reliable single chip sensing IC solution.

The ATS645 consists of a single-shot molded plastic package containing a single chip differential Hall-effect sensor IC, a Samarium Cobalt magnet, and a flat ferrous pole piece. The two Hall elements are spaced 1.5 mm apart allowing the device to sense small gear teeth geometries. The magnetic gradient is measured by the passing of a ferrous object, converted to an analog voltage and processed to provide a digital output signal.

The ATS645 switches in response to differential magnetic signals created by ferrous gear teeth. The circuitry contains a sophisticated digital circuit to eliminate magnet and system offsets and to achieve true zero speed operation. This device makes speed sensing using a ferrous target with symmetrical teeth very simple and removes the third sense wire from the circuit.

The Hall IC/magnet configuration is integrally molded into a plastic sub-assembly that has been optimized for size, ease of assembly and manufacturability. This small package (8.0 mm diameter x 5.5 mm length) can be easily assembled and used in conjunction with a wide variety of gear shapes and sizes.

With the improvement of the sensor-to-sensor spacing, which has been decreased to 1.5 mm allowing the device to sense very small, symmetrical tooth geometries reliably, the ATS645 replaces Allegro's ATS640 and ATS641 devices.

The ATS645 is ideally suited for obtaining speed and duty cycle in ABS and transmission application gear-tooth-based configurations, and therefore is primarily targeted to the automotive marketplace. The sensor is also suited for applications within the industrial market, specifically applications such as treadmills and industrial machinery.

The ATS645 has a 22-week lead-time to market and is priced at $1.51 in quantities of 100,000.

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 can be found at


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