Details, datasheet, quote on part number: A643
DescriptionTrue Zero-Speed, Two-Wire, Miniature Gear-tooth Sensor
CompanyAllegro Micro Systems, Inc.
DatasheetDownload A643 datasheet
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Features, Applications
CONCEPTUAL DATASHEET (subject to change without notice)
True Zero-Speed, Two-Wire, Miniature Gear Tooth Sensor

The is an optimized Hall-effect sensing integrated circuit and magnet combination that provides a user-friendly solution for true zero-speed digital gear-tooth sensing in two-wire applications. The sensor consists of a single-shot molded plastic package that includes a samarium cobalt magnet, a pole piece, and a Hall effect IC that has been optimized to the magnetic circuit. This small package can be easily assembled and used in conjunction with a wide variety of gear shapes and sizes. The integrated circuit incorporates a dual element Hall-effect sensor and signal processing circuitry that switches in response to differential magnetic signals created by ferrous targets. The device contains a sophisticated compensating circuit to eliminate magnet and system offsets. Digital tracking of the analog signal is used to achieve true zero speed operation. A-D and D -A converters are used to adjust the device gain and offset at power up resulting in air gap independent switch-points, which greatly improves output accuracy. The regulated current output is configured for two-wire operation. This sensor is ideal for obtaining speed and duty cycle information in gear-tooth-based applications such as transmission speed sensing.

Supply Voltage, VCC 26.5 V* Reverse Supply Voltage, 18 V Operating Temperature Range, C* Storage Temperature, C Package Power Rating, 126 C/W Maximum Junction Temperature, TJ, continuous. C * Operation at increased supply voltages and temperatures

Fully optimized differential digital gear tooth sensor Single chip sensing IC for high reliability Internal current regulator for 2-wire operation Vibration immunity Small mechanical size (8 mm dia 5.5 mm length) Air gap independent switch-points Digital output representing gear profile Precise duty cycle over temperature Large operating air gaps <2 ms power up time AGC and reference adjust circuit True zero-speed operation Under-voltage lockout Wide operating voltage range Defined power-on state

Operating Characteristics: Valid over operating temperature range unless otherwise noted.

Characteristics Symbol Test Conditions Min. ELECTRICAL CHARACTERISTICS Supply Voltage Under Voltage Lockout Supply Zener Clamp Voltage Max Zener Pulse Current Supply Zener Resistance Supply Current I1 Supply Current I2 Supply Current Ratio VCC VCC(UV) IZ RZ ICC Low Current State: IccLow High Current State: IccHigh Low Current State: IccLow High Current State: IccHigh Ratio of High Current to Low Current Operating, 165 C VCC 5 V IZT 1 mA Continuous t=20mS Pulse Mode TBD Vcc<V cc Min V mA Limits Typ. Max. Units


Power Up Time is the time required to complete the internal automatic offset adjust; the DAC's are then ready for peak acquisition. Rev 2.1, MHN, 09.May.2003 Page of 9

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts (508) 853-5000 Copyright 1993, 1995 Allegro MicroSystems, Inc.

Operating Characteristics: Valid with Reference Target unless otherwise specified

Characteristics Symbol Test Conditions Min. SWITCH POINT CHARACTERISTICS Rotation Speed Bandwidth Operate Point Release Point CALIBRATION Initial Calibration AGC Disable DAC CHARACTERISTICS Dynamic Offset Cancellation PDAC / NDAC

Reference Target % of peak to peak referenced from PDAC to NDAC, AG < Agmax; % of peak to peak referenced from PDAC to NDAC, AG < Agmax;

Rising Output Edges for Accurate Edge Detection Rising Output Edges
60 Number of Bits for Tracking Both Positive and Negative Signal Peaks 9

The device will compensate magnetic and installation offsets to 80 gauss. Offsets greater than 80 gauss may cause inaccuracies in the output. Rev 2.1, MHN, 09.May.2003 Page of 9

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts (508) 853-5000 Copyright 1993, 1995 Allegro MicroSystems, Inc.


Some Part number from the same manufacture Allegro Micro Systems, Inc.
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A660 True Zero-Speed, Hall-effect Adaptive Gear-tooth Sensor Module
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