ATS673 datasheet(14/19 Pages) ALLEGRO

14 / 19 page

Self-Calibrating TPOS Gear Tooth Sensor Optimized

for Automotive Cam Sensing Applications

ATS673 and

ATS674

Allegro MicroSystems, Inc.

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

Sensor and Target Evaluation

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Tooth

Valley

1.0

2.0

3.0

4.0

5.0

6.0

Target Rotation (°)

Magnetic Map, Reference Target 8X with SE Package

AG (mm)

Air Gap Versus Magnetic Field, Reference Target 8X with SE Package

Magnetic Profile

In order to establish the proper operating specification for a par-

ticular sensor device and target system, a systematic evaluation

of the magnetic circuit should be performed. The first step is the

generation of a magnetic map of the target. By using a calibrated

device, a magnetic profile of the system is made. Figure 10 is a

magnetic map of the 8X reference target.

A pair of curves can be derived from this map data, and be used

to describe the tooth and valley magnetic field strength, B, versus

the size of the air gap, AG. This allows determination of the mini-

mum amount of magnetic flux density that guarantees operation

of the sensor, so the system designer can determine the maximum

allowable AG for the sensor and target system. One can also

determine the TPOS air gap capabilities of the sensor by compar-

ing the minimum tooth signal to the maximum valley signal.

Figure 10. Magnetic Data for the 8X Reference Target and SE package.

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