2D, Dual-Channel, Ultrasensitive Hall-Effect Latch

A1262

10

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

FUNCTIONAL DESCRIPTION

Operation

The outputs of the A1262 switch low (turn on) when the cor-

responding Hall element is presented with a perpendicular south

magnetic field of sufficient strength. OUTPUTA switches low if

PUTB switches low if the Y-axis direction (A1262 with default

switch high (turn off) when the strength of a perpendicular north

of the device. See Figure 1.

Removal of the magnetic field will leave the device output

This built-in hysteresis allows clean switching of the output even

in the presence of external mechanical vibration and electrical

noise. The device will power-on in the low output state, even

Unlike dual-planar Hall-effect sensors, which have two planar

Hall-effect sensing elements spaced apart across the width of the

package, both the vertical and planar sensing elements on the

A1262 are located in essentially the same location on the IC.

V+

V

OUT(OFF)

V

OUT(ON)

B-

0

B+

B

HYS

Figure 1: Switching Behavior of Latches

On the horizontal axis, the B+ direction indicates increasing

south polarity magnetic field strength, and the B– direction

indicates decreasing south polarity field strength (including

the case of increasing north polarity

With dual-planar Hall sensors, the ring magnet must be properly

designed and optimized for the physical Hall spacing (distance)

in order to have the outputs of the two latches to be in quadra-

ture, or 90 degrees out of phase. With the A1262, which uses one

planar and one vertical Hall-effect sensing element, no target

optimization is required. When the face of the IC is facing the

ring magnet, the planar Hall senses the magnet poles and the

vertical Hall senses the transition between poles, therefore the

Figure 2: Ring magnet optimized for a dual-planar Hall-effect sensor resulting in output

quadrature also results in quadrature for the A1262.

Dual-Planar

Sensor

A1262