10

ATS643-DS, Rev. 1

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

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

ATS643LSH

induced by the target and sensed by the Hall elements. When

higher or lower level, it triggers sensor switch turn-on and turn-

off. As shown in figure 3, when the switch is in the off state, as

t+

V+

(A) TEAG varying; cases such as

eccentric mount, out-of-round region,

normal operation position shift

typically resulting in the sensor

0

360

Target Rotation (°)

Hysteresis Band

(Delimited by switchpoints)

V+

Larger

TEAG

Smaller

TEAG

Sensor

Target

Larger

TEAG

Target

Sensor

Smaller

TEAG

Smaller

TEAG

As shown in panel C of figure 4, threshold levels for the ATS643

switchpoints are established dynamically as function of the

peak input signal levels. The ATS643 incorporates an algorithm

that continuously monitors the system and updates the switch-

ing thresholds accordingly. The switchpoint for each edge is

determined by the detection of the previous two edges. In this

manner, variations are tracked in real time.

Figure 4. The Continuous Update algorithm allows the Allegro sensor to immediately interpret and adapt to significant variances in the magnetic field

generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and

similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently

As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the sensor as a varying magnetic field, which

Determinant

Peak Values

1

2

3

4