AATS643LSH_06 Datasheet, PDF (12/16 Pages) Allegro MicroSystems – Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor with Continuous Update

ATS643LSH
Self-Calibrating, Zero-Speed Differential
Gear Tooth Sensor with Continuous Update
Start Mode Hysteresis. This feature helps to ensure optimal
self-calibration by rejecting electrical noise and low-amplitude
target vibration during initialization. This prevents AGC from
calibrating the sensor on such spurious signals. Calibration can
be performed using the actual target features.
A typical scenario is shown in figure 6. The hysteresis, PO_HYS,
is a minimum level of the peak-to-peak amplitude of the internal
analog electrical signal, V_PROC, that must be exceeded before the
ATS643 starts to compute switchpoints.
Target, Gear
1 ^{Sensor Position Relative to Target}
2
5
Target Magnetic Profile
Differential Signal, V_PROC
Start Mode Hysteresis, PO_HYS
B_RP(#1)
B_OP(#1)
B_OP(#2)
Output Signal, I_OUT
12
34
5
Figure 6. Operation of Start Mode Hysteresis
Position 1. At power-on, the ATS643 begins sampling V_PROC.
Position 2. At the point where the Start Mode Hysteresis is exceeded, the device begins to establish switching thresholds (B_OP and B_RP) using the Con-
tinuous Update algorithm. After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid V_PROC value exceeding the Start Mode
Hysteresis can be generated either by a legitimate target feature or by excessive vibration.
Position 3. In this example, the first switchpoint transition is through B_OP . and the output transitions from high to low.
If the first switchpoint transition had been through B_RP (such as position 4), no output transition would occur because I_OUT already would be in the high
polarity. The first transition would occur at position 5 (B_OP).
Allegro MicroSystems, Inc.
12
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Worcester, Massachusetts 01615-0036 [phone]
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