Two-Wire, Zero Speed

Differential Gear Tooth Sensor IC

ATS685LSH

8

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Determining Output Signal Polarity

In figure 2, the top panel, labeled Mechanical Position, represents

the mechanical features of the target gear and orientation to the

device. The bottom panel, labeled Device Output Signal, displays

the square waveform corresponding to the digital output signal

(current amplitude) that results from a rotating gear configured

as shown in figure 3. Referring to the target side nearest the face

of the sensor IC, the direction of rotation is: perpendicular to the

leads, across the face of the device, from the pin 1 side to the

pin 4 side.

Rotating Target

Brande

of Package

Pin 1

Pin 4

dFace

Figure 3. This figure depicts left-to-right (pin 1 to pin 4) direction of target

rotation.

Figure 4. Alternative Polarity Configurations Using Two-Wire Sensing.

The Output Polarity States table provides the permutations of output

ATS685

VCC

GND

V

CC

1

4

ATS685

VCC

GND

V

CC

1

4

I

CC

I

CC

Output Polarity States

High side

(VCC pin side)

High

Low

Low

High

Low side

(GND pin side)

High

High

Low

Low

V+

V+

I+