ATS643LSH datasheet(12/16 Pages) ALLEGRO

12 / 16 page

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

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, POHYS,

is a minimum level of the peak-to-peak amplitude of the internal

analog electrical signal, VPROC, that must be exceeded before the

ATS643 starts to compute switchpoints.

Figure 6. Operation of Start Mode Hysteresis

Position 1. At power-on, the ATS643 begins sampling VPROC.

Position 2. At the point where the Start Mode Hysteresis is exceeded, the device begins to establish switching thresholds (BOP and BRP) using the Con-

tinuous Update algorithm. After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid VPROC 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 BOP. and the output transitions from high to low.

If the first switchpoint transition had been through BRP (such as position 4), no output transition would occur because IOUT already would be in the high

polarity. The first transition would occur at position 5 (BOP).

BRP(#1)

BOP(#1)

BOP(#2)

Start Mode Hysteresis, POHYS

Output Signal, IOUT

Sensor Position Relative to Target

Target Magnetic Profile

Differential Signal, VPROC

Target, Gear

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