Three-Wire, Differential, Vibration Resistant

Sensor IC with Speed and Direction Output

ATS693LSG

9

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

FUNCTIONAL DESCRIPTION

Sensing Technology

The sensor IC contains a single-chip Hall-effect circuit that

supports a trio of Hall elements. These elements are used in

differential pairs to provide electrical signals containing informa-

tion regarding edge position and direction of target rotation. The

ATS693 is intended for use with ferromagnetic targets.

After proper power is applied to the sensor IC, it is capable of

providing digital information that is representative of the mag-

netic features of a rotating target. The waveform diagrams in

figure 4 present the automatic translation of the target profiles,

through their induced magnetic profiles, to the digital output

signal of the sensor IC.

Direction Detection

The sensor IC compares the relative phase of its two differential

channels to determine in which direction the target is moving.

The relative switching order is used to determine the direction,

which is communicated through the output protocol.

Data Protocol Description

When a target passes in front of the device (opposite the branded

face of the package case), the ATS693 generates an output pulse

for each tooth of the target. Speed information is provided by the

output pulse rate, while direction of target rotation is provided by

the duration of the output pulses. The sensor IC can sense target

movement in both the forward and reverse directions.

FORWARD ROTATION (SEE PANEL A IN FIGURE 3)

When the target is rotating such that a tooth near the sensor IC

passes from pin 4 to pin 1, this is referred to as forward rotation.

typical) pulse width.

REVERSE ROTATION (SEE PANEL B IN FIGURE 3)

When the target is rotating such that a tooth passes from pin 1 to

pin 4, it is referred to as reverse rotation. Reverse rotation is indi-

Figure 3: Target Rotation

Figure 4: Magnetic Profile

The magnetic profile reflects the features of the target, allowing the

sensor IC to present an accurate digital output.

Pin 1

Pin 4

Rotating Target

(Ferromagnetic)

Rotating Target

(Ferromagnetic)

Branded Face

of Package

Pin 1

Pin 4

Branded Face

of Package

A Channel

B Channel

A Channel

B Channel

Detected Channel Switching

Device Output Signal

Device Orientation to Target

(Pin 1

Side)

(Pin 4

Side)

IC

A Channel

Pole Piece

(Concentrator)

Package Case

Branded Face

(Top View of

Package Case)

Back-Biasing

Rare-Earth Pellet

IC

E1

E2

E3

North Pole

South Pole

Mechanical Position (Target moves past device pin 1 to pin 4)

This tooth

sensed earlier

This tooth

sensed later

+B

Target

Target Magnetic Profile

(A) Forward Rotation

(B) Reverse Rotation