High-Accuracy, Pulse-Width or AK Protocol

Hall-Effect Wheel Speed and Direction Sensor IC

A19302

10

Allegro MicroSystems

955 Perimeter Road

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

www.allegromicro.com

DESCRIPTION OF AK PROTOCOL

The A19302 will fulfill the requirements according to the AK

protocol specification “Requirement Specifications for Standard-

ized Interface for Wheel Speed Sensors with Additional Infor-

mation ‘AK-Protokoll’” version 4.0 with some modifications as

discussed in the following.

AK BIT DEFINITIONS

The AK protocol (-xAx variant) consists of 10 pulses. A single

speed pulse, 8 data bits, and a single parity bit. The speed pulse

and data bit definitions are described below.

Field

Abbreviation

Coding

Speed Pulse

SP

ICC(HIGH) if speed pulse, ICC(MID) if standstill pulse

Bit Number

Field

Abbreviation

Coding

Post-Power-On

Default Value

0

Air Gap Reserve

LR

1 if Gpkpk < BLR(pk-pk), 0 otherwise

0

1

Status Mode

M

1 if not in running mode, 0 otherwise

1

2

Overtemperature

OT

1 if overtemperature, 0 otherwise

0

3

Validity of the Direction of Rotation

GDR

1 if direction is valid, 0 otherwise

0

4

Direction

DR

1 if forward rotation, 0 if reverse rotation

0

5

Air Gap Indication

LM0

LM LSB

0

6

Air Gap Indication

LM1

LM

0

7

Air Gap Indication

LM2

LM MSB

0

8

Parity

P

1 if parity incl. parity bit is even, 0 otherwise

1

LM AIR GAP TABLE

Data bits [5:7] report the air gap indication. These bits give 8 air

gap ranges in respect to the measured peak to peak magnetic field

(BDIFF(pk-pk)).

LM2

LM1

LM0

Threshold

Value (Typ.)

Units

0

0

0

≤ 12

G

0

0

1

> 12

G

0

1

0

> 18

G

0

1

1

> 24

G

1

0

0

> 36

G

1

0

1

> 54

G

1

1

0

> 78

G

1

1

1

> 111

G