Position Sensor IC

with Speed and Direction Output

ATS696PSM

8

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

FUNCTIONAL DESCRIPTION

Sensing Technology

The sensor IC contains three Hall elements used in three differ-

ential pairs to provide an electrical output signal containing infor-

mation regarding target edge position and direction of rotation.

Target Profiling

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

of providing digital information that is representative of the

mechanical or magnetic features of a rotating target. The wave-

form diagrams in Figure 7 present the automatic translation of

the target profiles, from their induced magnetic profiles to the

digital output signal of the sensor IC. Three differential mag-

netic profiles are used to determine the location of the switching

feature as well as the direction of rotation. While the location of

the switching feature is determined from the differential magnetic

profile (referred to as the speed channel), the direction of rotation

is determined by the relative amplitude comparison of two low

resolution normalized direction channels.

Direction Detection

The sensor IC compares the relative amplitude values of the two

low resolution normalized direction signals at the speed channel

switchpoint location to determine which direction the target is

rotating. The direction of rotation is then communicated through

the output pulse width. While in calibration mode, direction

information is not available. As a result of this, forward output

the true target rotation direction.

NOTE: For proper functionality, the output must be programmed

such that the signature region is a non-switching feature (see

Application Information section).

The sensor IC can be programmed such that the output will

pin 1 to pin 3 (Option F) or from pin 3 to pin 1 (Option R). This

is illustrated in Figure 8, with the arrow on the target indicating

direction of rotation.

Figure 7: Magnetic Profile.

The magnetic profile reflects the features of the target, allowing

the sensor IC to present an accurate digital output.

Detected Channel Switching

Device Output

Direction

Channel

Direction

Channel

Speed

Channel

Speed

Channel

Device Orientation to Target

(Pin 1

Side)

(Pin 3

Side)

IC

Speed Channel

Element Pitch

Pole Piece

(Concentrator)

Package Case

Branded Face

(Top View of

Package Case)

Back-Biasing

Rare-Earth Pellet

Speed Channel

Element Pitch

Mechanical Position (Target moves past device pin 1 to pin 3)

Target

(Ferromagnetic)

This tooth

sensed earlier

This tooth

sensed later

E1

E2

E3

+B

Target Magnetic Profile

North Pole

South Pole

Figure 8: Rotation Direction Definitions

Option F

Forward pulses (t

Pin 1

Pin 3

Rotating Target

(Ferromagnetic)

Rotating Target

(Ferromagnetic)

Option R

Forward pulses (t

Pin 1

Pin 3

Branded Face

of SM Package

Branded Face

of SM Package