HMC5843 Datasheet, PDF (6/19 Pages) Honeywell Solid State Electronics Center – 3-Axis Digital Compass IC

HMC5843
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.
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