ATS665LSG

TRUE ZERO-SPEED GEAR TOOTH SENSOR

Final Version, Rev 2.0; MN; 19Dec05

Page 12

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc.

TARGET DESIGN

For the generation of adequate magnetic field levels to maximize air gap performance, the following recommendations

should be followed in the design and specification of targets.

•

Tooth width > 2 mm

•

Valley width > 2 mm

•

Valley depth > 2 mm

•

Gear thickness > 3 mm

•

Target material must be low carbon steel

Though these parameters apply to targets of traditional geometry (radially oriented teeth with radial sensing), they can be

applied to stamped targets as well. For stamped geometries with axial sensing, the valley depth is intrinsically infinite so

the criteria for tooth width, valley width, material thickness (can be < 3 mm) and material specification need only be

considered.

SENSOR EVALUATION: ACCURACY

While the update algorithm will allow the sensor the adapt to system changes (i.e. air gap increase), major changes in air

gap can adversely affect switching performance. When characterizing sensor performance over a significant air gap range,

be sure to re-power the device at each air gap. This ensures that self-calibration occurs for each installation condition.

See the section entitled Characteristic Data for typical duty cycle performance.