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A3230-DS

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

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

Chopper-Stabilized Hall Effect Bipolar Switch

A3230

Functional Description

V+

0

V+

0

V+

0

B+

B–

B+

B– 0

0

B+

B–

0

VCC

Sensor Output

GND

VOUT

A3230

0.1 µF

Operation

The output of these devices switches low (turns on) when a

magnetic field perpendicular to the Hall sensor exceeds the

30 mA. When the magnetic field is reduced below the release

ence in the magnetic operate and release points is the hysteresis,

ing of the output even in the presence of external mechanical

vibration and electrical noise.

There are three switching modes for bipolar devices, referred to

as latch, unipolar switch, and negative switch. Mode is deter-

mined by the switchpoint characteristics of the individual device.

Note that, as shown in figure 1, these switchpoints can lie in

either north or south polarity ranges. The values of the magnetic

parameters for the A3230 are specified in the Magnetic Charac-

teristics table, on page 3.

Bipolar devices typically behave as latches (although these

devices are not guaranteed to do so). In this mode, magnetic

fields of opposite polarity and equivalent strengths are needed

to switch the output. When the magnetic fields are removed

(B

→ 0) the device remains in the same state until a magnetic

Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as that shown in panel D. Panel A

such as the A3230, can operate in any of the three modes.

(A)

(B)

(C)

(D)

field of the opposite polarity and of sufficient strength causes

it to switch. The hysteresis of latch mode behavior is shown in

panel A of figure 1.

In contrast to latching, when a device exhibits unipolar switch-

ing, it only responds to a south magnetic field. The field must

back to the high state, as shown in panel B of figure 1. Devices