A1225LLTTR-T Ver la hoja de datos (PDF) - Allegro MicroSystems

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A1225LLTTR-T

Hall Effect Latch for High Temperature Operation

Allegro MicroSystems 

A1225, A1227

and A1229

Hall Effect Latch for High Temperature Operation

Functional Description and Application Information

Switching Behavior

The output of the A1225, A1227, and A1229 devices switches

low (turns on) when a magnetic field perpendicular to the Hall

element exceeds the operate point threshold, BOP (see figure 1).

After turn-on, the output is capable of sinking 25 mA and the

output voltage is VOUT(sat). Notice that the device latches; that is,

a south pole of sufficient strength towards the branded surface

of the device turns the device on, and the device remains on with

removal of the south pole.

Application Information

The simplest form of magnet that will operate these devices is a

ring magnet, as shown in figure 2. Other methods of operation

are possible.

In three-wire applications the device output is connected through

a pull-up resistor to the supply pin or separate battery voltage

(figure 3). Switching of the output signal indicates sufficient

change of the magnetic field.

When the magnetic field is reduced below the release point, BRP ,

the device output goes high (turns off). The difference between

the magnetic operate point and release point is the hysteresis,

BHYS, of the device. This built-in hysteresis allows clean switch-

ing of the output, even in the presence of external mechanical

vibration and electrical noise.

When the device is powered-on in the hysteresis range, less than

BOP and higher than BRP, the device output goes high. The correct

output state is attained after the first excursion beyond BOP or

BRP .

V+

VCC

0

B–

BHYS

VOUT(sat)

B+

Figure 1. Output switching characteristics

Figure 2. Typical magnetic target configuration using a ring magnet

V+

CBYPASS

VPULLUP

A122x

VCC

VOUT

GND

RPULLUP

Device

Output

CL

(Optional)

Figure 3. Typical 3-wire application circuit

Allegro MicroSystems, Inc.

9

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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