HMC5983-DEM Datasheet, PDF (10/28 Pages) Honeywell Accelerometers – 3-Axis Digital Compass IC

HMC5983
PERFORMANCE
The following graph(s) highlight HMC5983’s performance.
Typical Noise Floor (Field Resolution)
Dev100Readings
3
2.5
2
Ga) ^1.5
-Std
Resolution
(m ¹
0.5
0
HMC5983 Resolution
0 1234567
Gain
Ex1pAovng. (1)
Ex2pAovng. (2)
Ex4pAovng. (4)
Ex8pAovng. (8)
BASIC DEVICE OPERATION
Anisotropic Magneto-Resistive Sensors
The Honeywell HMC5983 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 in the pinout
diagram) that will provide positive voltage change with magnetic fields increasing in the sensitive direction. Because the
output is only proportional to the magnetic field component along its axis, additional sensor bridges are placed at
orthogonal directions to permit accurate measurement of magnetic field in any orientation.
Self Test
To check the HMC5983 for proper operation, a self test feature is incorporated in which the sensor is internally excited
with a nominal magnetic field (in either positive or negative bias configuration). This field is then measured and reported.
This function is enabled and the polarity is set by bits MS[n] in the configuration register A. An internal current source
generates a DC current (about 10 mA) from the VDD supply. This DC current is applied to the offset straps of the
magneto-resistive sensor, which creates an artificial magnetic field on the sensor. The difference of this measurement
and the measurement of the ambient field will be put in the data output register for each of the three axes. By using this
built-in function, the manufacturer can quickly verify the sensor’s full functionality after the assembly without additional test
setup. The self test results can also be used to estimate/compensate the sensor’s sensitivity drift due to temperature.
For each “self test measurement”, the ASIC:
1. Sends a “Set” pulse
2. Takes one measurement (M1)
3. Sends the (~10 mA) offset current to generate the (~1.1 Gauss) offset field and takes another
measurement (M2)
4. Puts the difference of the two measurements in sensor’s data output register:
Output = [M2 – M1] (i.e. output = offset field only)
See SELF TEST OPERATION section later in this datasheet for additional details.
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