ATS673 datasheet(12/19 Pages) ALLEGRO

12 / 19 page

Self-Calibrating TPOS Gear Tooth Sensor Optimized

for Automotive Cam Sensing Applications

ATS673 and

ATS674

Allegro MicroSystems, Inc.

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

Switchpoints

Switchpoints in the ATS673 and ATS674 are established dynami-

cally as a percentage of the amplitude of the signal, VPROC, after

normalization with AGC. Two DACs track the peaks of VPROC

(see the Update subsection).

The switching thresholds are established at fixed percentages

of the values held in the two DACs. The value of the thresholds

has been carefully selected, where the signal is steepest and least

affected by air gap variation, thus providing the most accurate

and consistent switching.

The low hysteresis, 10%, provides high performance over vari-

ous air gaps while maintaining immunity to false switching on

noise, vibration, backlash, or other transient events.

Figure 8 graphically demonstrates the establishment of the

switching threshold levels. Because the thresholds are estab-

lished dynamically as a percentage of the peak-to-peak signal,

the effect of a baseline shift is minimized.

100

BOP%

V+

Device

State

-LT option

Target

Mechanical

Profile

BRP%

Off

-HT option

Off

Figure 8. Switchpoint Relationship to Thresholds.The device switches

when VPROC passes a threshold level, BOP or BRP, while changing in the

corresponding direction: increasing for a BOP switchpoint, and decreasing

for a BRP switchpoint.

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