10

651LSH-DS

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

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

Two-Wire Self-Calibrating Differential Speed and Direction Sensor with Vibration Immunity

ATS651LSH

Applications Information

Data Protocol Description

Rotation Right. Referring to figure 1, a ferrous target passes in

front of the sensor (not shown) in the direction indicated. Each

tooth of the target generates a pulse from the sensor. Each pulse

provides speed and direction data. Speed is provided by the

pulse rate, while direction is obtained by measuring the width

of the pulses. A 45 μs pulse indicates rotation in the clockwise

direction.

Rotation Left. Referring to figure 2, when the target changes

direction, the sensor outputs a current pulse of or 90 μs, twice

as long as the Rotation Right pulse width. The maximum speed

is limited by the width of the pulse and the shortest Low-State

Duration the controller can resolve.

Figure 1. Target rotation to the right (CW) relative to the sensor gives forward speed.

Figure 2. Target rotation to the left (CCW) relative to the sensor gives reverse speed.

45 μs

45 μs

45 μs

45 μs

90 μs

90 μs

90 μs

90 μs