Two-Wire, Zero-Speed

Differential Gear Tooth Sensor IC

ATS684LSN

9

Allegro MicroSystems, LLC

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, repre-

sents 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 config-

ured as shown in Figure 4. 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 3 side.

Figure 4: Left-to-Right, Pin 1 to Pin 3 (top) and Right-to-

Left, Pin 3 to Pin 1 (bottom) Direction of Target

Rotation.

Figure 5: Alternative Polarity Conf igurations Using

Two-Wire Sensing.

The Output Polarity States table provides the permutations of output

inverted.

V

DD

V

DD

I

CC

I

CC

11

VCC

VCC

ATS684

ATS684

GND

GND

33

R

LOAD

100

W

R

LOAD

100

W

C

LOAD

C

LOAD

Output Polarity States

High side

(VCC pin side)

High

Low

Low

High

Low side

(GND pin side)

High

High

Low

Low

I+

V+

V+

I

CC

V

SENSE(LowSide)

V

SENSE(HighSide)

Panel A

Panel B

Panel C