ASIL-Compliant Hall-Effect Wheel Speed Sensor IC

with Speed and Direction Output

A19300

11

Allegro MicroSystems

955 Perimeter Road

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

www.allegromicro.com

BOP

BOP

BRP

BRP

Device Orientation

to Target

Package Case Branded Face

Target Magnetic Profile

+B

–B

Mechanical Position (Target moves past device pin 1 to pin 2)

Target

(Radial Ring Magnet)

IC Internal Differential Analog Signals, BDIFF

Detected Channel Switching

Output (pulse protocol)

(Pin 2 Side)

(Pin 1 Side)

(Top View of

Package Case)

IC

This pole

sensed later

This pole

sensed earlier

N

SS

Speed Channel

Element Pitch

Channel A

Channel A

Channel B

Channel B

Package Case Branded Face

(Pin 2 Side)

(Pin 1 Side)

(Top View of

Package Case)

Back-Biasing Magnet

Speed Channel

Element Pitch

This tooth

sensed

earlier

This tooth

sensed

later

Device Orientation to Target

Mechanical Position (Target moves past device pin 1 to pin 2)

Target

(Gear)

+B

Target Magnetic Profile

IC

South Pole

North Pole

BOP

BOP

BRP

BRP

IC Internal Differential Analog Signals, BDIFF

Detected Channel Switching

Output (pulse protocol)

Channel A

Channel A

Channel B

Channel B

Figure 9: Basic Operation

Channel A or Channel B can be used as the output switching channel.

This is determined on startup by the first channel that switches.

The non-switching channel is used for direction detection.