Dynamic, Self-Calibrating, Threshold-Detecting, Differential

Speed and Direction Hall-Effect Gear Tooth Sensor IC

ATS657

10

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

During normal running mode, vibration can interfere with the

direction detection functions. In that case, during the vibration the

device may continue to output speed data with non-directional

pulses.

If the vibration that occurs has a large enough amplitude such

switchpoints, non-direction pulses will be outputted during the

vibration, as shown in figure 5.

If the vibration has a low enough amplitude such that its posi-

no switchpoint updating occurs until the vibration becomes large

does occur, a single direction pulse may be outputted, however,

regardless of whether or not that single pulse occurs, non-direction

pulses are outputted throughout the remainder of the vibration.

Figure 6. Small amplitude vibration during Running mode operation

Figure 5. Large amplitude vibration during Running mode operation

Operation During Running Mode Vibration

+V

Switchpoint

Hysteresis

+t

+t

Normal Rotation

Vibration

}

+I

+V

Switchpoint

Hysteresis

+t

+t

Normal Rotation

Vibration

}

+I