3260

2-WIRE, CHOPPER-STABILIZED,

PRECISION HALL-EFFECT

BIPOLAR SWITCH

www.allegromicro.com

7

FUNCTIONAL DESCRIPTION

Chopper-Stabilized Technique. These devices use a

proprietary dynamic offset cancellation technique, with an

internal high-frequency clock to reduce the residual offset

voltage of the Hall element that is normally caused by device

overmolding, temperature dependencies, and thermal stress.

This technique produces devices that have an extremely stable

quiescent Hall output voltage, are immune to thermal stress, and

have precise recoverability after temperature cycling. This

technique will also slightly degrade the device output repeat-

ability.

The Hall element can be considered as a resistor array

similar to a Wheatstone bridge. A large portion of the offset is

a result of the mismatching of these resistors. The chopper-

stabilizing technique cancels the mismatching of the resistors by

changing the direction of the current flowing through the Hall

plate and Hall voltage measurement taps, while maintaining the

Hall-voltage signal that is induced by the external magnetic

flux. The signal is, then, captured by a sample-and-hold circuit.

Operation. The output of these devices turns ON when a

magnetic field (north pole) perpendicular to the Hall sensor

output will source current equal to the device operating current

will source current equal to the Hall-effect sensor operating

difference in the magnetic operate and release points is the

switching of the output even in the presence of external me-

chanical vibration or electrical noise.

Applications. It is strongly recommended that an external

bypass capacitor be connected (in close proximity to the Hall

sensor) between the supply and ground of the device to reduce

both external noise and noise generated by the chopper-

stabilization technique.

Extensive applications information on magnets and Hall-

effect sensors is also available in the Allegro Electronic Data

Book AMS-702 or Application Note 27701.

Dwg. EH-012

REG

X

+V

HALL

VOLTAGE

B

+

—

Dwg. AH-011-2

0

+B

0

FLUX DENSITY

Dwg. GH-034-6

-B

+I

100

Ω

Dwg. EH-011-2A

0.1

µF

SUPPLY

X

'UA' PACKAGE

0.95 V

–

+