ATS645: True Zero Speed Gear-Tooth Sensor IC

This device is no longer in production. The device should not be purchased for new design applications. Samples are no longer available. Date of status change: November 10, 2014.

Recommended substitution: For existing customer transition, and for new customers or new applications, contact Allegro Sales.

The components in speed sensing applications continue to diminish in size to meet spatial constraints and weight reduction requirements. As the geometries of gears become smaller, this can compromise the capabilities of a gear speed sensor IC. The ATS645 Hall-element-to-Hall-element spacing of only 1.5 mm makes this device uniquely capable of accommodating very fine-pitch gears. In addition, the ATS645 signal peak-detecting algorithm supports consistent switching at relatively large air gaps, where the peak-to-peak amplitude is small. These features make the ATS645 the ideal solution to detect the speed of fine-pitch targets such as those found in ABS (antilock braking) systems.

The ATS645 combines a Hall-effect sensing integrated circuit and magnet to provide a manufacturer-friendly solution for true zero-speed digital gear-tooth sensing in two-wire applications. The device consists of a single-shot molded plastic package that includes a samarium cobalt magnet, a pole piece, and a Hall-effect integrated circuit that has been optimized to the magnetic circuit. This small package can be assembled simply and used in conjunction with a wide variety of gear shapes and sizes.

The integrated circuit incorporates a dual-element Hall effect sensor IC as well as signal processing that switches the output state in response to changes in the magnetic gradients 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 (U.S. Patent 5,917,320). A-D and D-A converters are used to adjust the device gain at power-on and to allow switching independent of the breadth of the air gap.

The regulated current output is configured for two wire applications, requiring one less wire for operation than do switches with the more traditional open-collector output.The package is available in a lead (Pb) free version, with 100% matte tin leadframe plating.


Astrorep Inc. (Allegro and Sanken Semiconductors, Sanken Power Supplies)
141 John Street, Suite 300
Babylon, NY 11702
Phone: (631)422-2500
Fax: (631)422-2504

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  • Features and BenefitsFeatures and Benefits
  • PackagingPackaging
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  • NewsNews
  • Fully optimized differential digital gear tooth sensor IC
  • Single chip sensing IC for high reliability
  • Internal current regulator for 2 wire operation
  • Small mechanical size (8 mm diameter x 5.5 mm depth)
  • Air gap independent switch points
  • Digital output representing gear profile
  • Precise duty cycle signal over operating temperature range
  • Large operating air gaps
  • Automatic Gain Control (AGC)
  • Automatic Offset Adjustment (AOA)
  • True zero speed operation
  • Under-voltage lockout
  • Wide operating voltage range
  • Defined power-on state

The package is available in a lead (Pb) free version, with 100% matte tin leadframe plating.

SH SIP 4 pin

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Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
ATS645LSHTN-I1-T 4-lead SIP -40°C to 150°C Yes View Data Discontinued Contact your
local sales rep
Check Stock
ATS645LSHTN-I2-T 4-lead SIP -40°C to 150°C Yes View Data Discontinued Contact your
local sales rep
Check Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.

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