3059 Datasheet, PDF (4/8 Pages) Allegro MicroSystems – HALL-EFFECT GEAR-TOOTH SENSORS -AC COUPLED

3059 AND 3060
HALL-EFFECT
GEAR-TOOTH SENSORS
—AC COUPLED
TYPICAL OPERATING CHARACTERISTICS
SUPPLY CURRENT
20
13
V_CC = 18 V
12
15
B ≤ B _RP
11
10
10
5
9
T_A = +25°C
B < B_RP
0
-50 -25
0
25
50
75
100
AMBIENT TEMPERATURE IN °C
125 150
Dwg. GH-028-1
8
0
5
10
15
20
25
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-031-1
APPLICATIONS INFORMATION
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.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]