HMC5843

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SINGLE SUPPLY REFERENCE DESIGN

BASIC DEVICE OPERATION

Anisotropic Magneto-Resistive Sensors

The Honeywell HMC5843 magnetoresistive sensor circuit is a trio of sensors and application specific support circuits to

measure magnetic fields. With power supply applied, the sensor converts any incident magnetic field in the sensitive axis

directions to a differential voltage output. The magnetoresistive sensors are made of a nickel-iron (Permalloy) thin-film and

patterned as a resistive strip element. In the presence of a magnetic field, a change in the bridge resistive elements

causes a corresponding change in voltage across the bridge outputs.

These resistive elements are aligned together to have a common sensitive axis (indicated by arrows on the pinouts) that

will provide positive voltage change with magnetic fields increasing in the sensitive direction. Because the output only is in

proportion to the one-dimensional axis (the principle of anisotropy) and its magnitude, additional sensor bridges placed at

orthogonal directions permit accurate measurement of arbitrary field direction.

Self Test

An offset strap is designed for self test function. The offset strap measures nominally 13 ohms, and requires 10mA for

each gauss of induced field. The straps will easily handle currents to buck or boost fields through the ±4 gauss linear

measurement range, but designers should note the extreme thermal heating on the sensor die when doing so.