HALL-EFFECT

GEAR-TOOTH SENSORS

—AC COUPLED

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

4

TYPICAL OPERATING CHARACTERISTICS

SUPPLY CURRENT

0

20

15

10

5

0

25

5075100

AMBIENT TEMPERATURE IN

°°°°C

-50

Dwg. GH-028-1

125

-25

V

= 18 V

CC

150

B

≤ B

RP

A gear-tooth sensing system consists of the sensor

IC, a back-biasing magnet, and a target. The system

requirements are usually specified in terms of the effective

working air gap between the package and the target (gear

teeth), the number of switching events per rotation of the

target, temperature and speed ranges, minimum pulse

duration or duty cycle, and switch point accuracy. Careful

choice of the sensor IC, magnet material and shape,

target material and shape, and assembly techniques

enables large working air gaps and high switch-point

accuracy over the system operating temperature range.

Naming Conventions. With a south pole in front of

the branded surface of the sensor or a north pole behind

the sensor, the field at the sensor is defined as positive.

As used here, negative flux densities are defined as less

than zero (algebraic convention), e.g., -100 G is less than

+50 G.

Magnet Biasing. In order to sense moving non-

magnetized ferrous targets, these devices must be back-

biased by mounting the unbranded side on a small

permanent magnet. Either magnetic pole (north or south)

can be used.

The devices can also be used without a back-biasing

magnet. In this configuration, the sensor can be used to

detect a rotating ring magnet such as those found in

brushless dc motors or in speed sensing applications.

Here, the sensor detects the magnetic field gradient

created by the magnetic poles.

APPLICATIONS INFORMATION

0

8

SUPPLY VOLTAGE IN VOLTS

Dwg. GH-031-1

13

12

11

10

9

510

15

20

25

T = +25

°C

A