A3260LUA(2006) データシートの表示（PDF） - Allegro MicroSystems

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A3260LUA
(Rev.:2006)

2-Wire Chopper Stabilized Precision Hall Effect Bipolar Switch

Allegro MicroSystems 

3260

2-WIRE, CHOPPER-STABILIZED,

PRECISION HALL-EFFECT

BIPOLAR SWITCH

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

exceeds the release point threshold (BRP). After turn-ON, the

output will source current equal to the device operating current

plus a current source (IGND(H)). When the magnetic field is

increased (south pole) above the operate point (BOP), the output

will source current equal to the Hall-effect sensor operating

current with the current source turned OFF (IGND(L)). Note

especially that release can occur when the magnetic field is

removed but to ensure release, a field reversal is required. The

difference in the magnetic operate and release points is the

hysteresis (Bhys) of the device. The hysteresis allows clean

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

chanical vibration or electrical noise.

Powering up in the absence of a magnetic field (less than

BOP and higher than BRP) will allow an indeterminate output

state. The correct state is warranted after the first excursion

beyond BOP or BRP.

Bipolar switches may switch on removal of field but

require field reversal for reliable operation over temperature

range; latches will not switch on removal of magnetic field.

REG

X

B

+V

Dwg. EH-012

—

HALL

VOLTAGE

+

Dwg. AH-011-2

+I

IOUT + ICC

ICC

0

-B

BRP

BOP

0

FLUX DENSITY

+B

Dwg. GH-034-6

www.allegromicro.com

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