A3211 データシートの表示（PDF） - Allegro MicroSystems

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A3211

Micropower, Ultra-sensitive Hall-ef fect Switches

Allegro MicroSystems 

A3211 and

A3212

Micropower, Ultrasensitive

Hall Effect Switch

FUNCTIONAL DESCRIPTION (cont'd)

Operation. The output of the A3212 switches low (turns on)

when a magnetic field perpendicular to the Hall sensor exceeds

the operate point BOPS (or is less than BOPN). After turn-on, the

output is capable of sinking up to 1 mA and the output voltage

is VOUT(ON). When the magnetic field is reduced below the

release point BRPS (or increased above BRPN), the device output

switches high (turns off). The difference in the magnetic operate

and release points is the hysteresis (Bhys) of the device. This

built-in hysteresis allows clean switching of the output even

in the presence of external mechanical vibration and electrical

noise. The A3211 functions in the same manner, except the out-

put voltage is reversed from the A3212, as shown in the figures

to the right.

As used here, negative flux densities are defined as less than

zero (algebraic convention), i.e., -50 G is less than +10 G.

Applications. Allegro's pole-independent sensing technique

allows for operation with either a north pole or south pole mag-

net orientation, enhancing the manufacturability of the device.

The state-of-the-art technology provides the same output polarity

for either pole face.

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. This

is especially true due to the relatively high impedance of battery

supplies.

The simplest form of magnet that will operate these devices

is a bar magnet with either pole near the branded surface of the

device. Many other methods of operation are possible. Exten-

sive applications information for Hall-effect sensors is available

in:

• Hall-Effect IC Applications Guide, Application Note 27701;

• Hall-Effect Devices: Soldering, Gluing, Potting, Encapsu-

lating, and Lead Forming, Application Note 27703.1;

• Soldering of Through-Hole Hall-Sensor Dervices, Application

Note 27703; and

• Soldering of Surface-Mount Hall-Sensor Devices, Application

Note 27703.2.

All are provided at

www.allegromicro.com

A3211

OUTPUT OFF

5V

MAX

BRPN

BRPS

OUTPUT OFF

B OPN

OUTPUT ON

B OPS

0

-B

0

+B

MAGNETIC FLUX

A3212

5V

MAX

B OPN

OUTPUT OFF

B OPS

OUTPUT ON

0

-B

BRPN

BRPS

0

MAGNETIC FLUX

OUTPUT ON

+B

OUTPUT

0.1 ∝F

S UP P LY

(3 V BATTE R Y)

Dwg. E H-013-2

Allegro MicroSystems, Inc.

8

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

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