AATS643LSH_06 Datasheet, PDF (11/16 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
Power-On State Operation. The ATS643 is guaranteed to
power-on in the high current state, I_CC(High).
Initial Edge Detection. The device self-calibrates using the
initial teeth sensed, and then enters Running mode. This results
in reduced accuracy for a brief period (less than four teeth),
however, it allows the device to optimize for continuous update
yielding adaptive sensing during Running mode. As shown in
figure 5, the first three high peak signals are used to calibrate
AGC. However, there is a slight variance in the duration of ini-
tialization, depending on what target feature is nearest the sensor
when power-on occurs.
Target
(Gear)
Sensor Position _{1 2 3 4}
Power-on
over valley 1
V_PROC
Output
Start Mode
Hysteresis
Overcome
Power-on
at rising edge ₂
AGC Calibration
V_PROC
Output
Running Mode
Start Mode
Hysteresis
Overcome
Power-on
over tooth ₃
AGC Calibration
V_PROC
Output
Running Mode
Start Mode
Hysteresis
Overcome
Power-on
at falling edge 4
AGC Calibration
V_PROC
Running Mode
Start Mode
Hysteresis
Overcome
Output
AGC Calibration
Running Mode
Figure 5. Power-on initial edge detection. This figure demonstrates four typical power-on scenarios. All of these examples assume that the target is
moving relative to the sensor in the direction indicated. The length of time required to overcome Start Mode Hysteresis, as well as the combined effect
of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when
AGC calibration begins. Three high peaks are always required for AGC calibration.
Allegro MicroSystems, Inc.
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115 Northeast Cutoff, Box 15036
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www.allegromicro.com