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

HMC5843
SELF TEST OPERATION
To check the HMC5843 for proper operation, a self test feature in incorporated in which the sensor offset straps are
excited to create a nominal field strength (bias field) to be measured. To implement this self test, the least significant bits
(MS1 and MS0) of configuration register A are changed from 00 to 01 (0x12 or 0b000xxx01). By placing the mode register
into single-conversion mode (0x01), two data acquisition cycles will be made on each magnetic vector. The first
acquisition will be a set pulse followed shortly by measurement data of the external field. The second acquisition will have
the offset strap excited in the positive bias mode (~5.5mA in offset straps) to create about a 0.55 gauss self test field plus
the external field. The first acquisition values will be subtracted from the second acquisition, and the net measurement will
be placed into the data output registers.
If the configuration register B is left at the factory default value of 0x20, values around +715 ADC counts (0.55Ga * 1300
counts/Ga) will be placed in the data output registers. To leave the self test mode, change MS1 and MS0 bit of the
configuration register A back to 0x00. Also change the mode register if single-conversion mode is not the intended next
mode of operation.
SCALE FACTOR CALIBRATION
Using the method described above in section SELF TEST OPERATION, user can scale sensors’ sensitivity to match each
other. Since placing device in positive bias mode (or alternatively negative bias mode) applies the same artificial field on
all three axis, the resulting ADC measurement in data output registers can be used to scale the sensors.
EXTERNAL CAPACITORS
The two external capacitors should be ceramic type construction with low ESR characteristics. Reservoir capacitor C1 is
nominally 4.7 micro-farads in capacitance, with the set/reset capacitor C2 nominally 0.22 micro-farads in capacitance.
Low ESR characteristics may not be in many smallest size SMT ceramic capacitors (0402), so be prepared to up-size the
capacitors to gain Low ESR characteristics.
ORDERING INFORMATION
Ordering Number
HMC5843
HMC5843-TR
HMC5843-demo
HMC5843-eval
Product
3-Axis Digital Compass IC
Tape and Reel 2.5k pieces/reel
Demonstration Kit
Evaluation Board
FIND OUT MORE
For more information on Honeywell’s Magnetic Sensors visit us online at www.honeywell.com/magneticsensors or contact
us at 800-323-8295 (763-954-2474 internationally).
The application circuits herein constitute typical usage and interface of Honeywell product. Honeywell does not warranty or assume liability of customer-
designed circuits derived from this description or depiction.
Honeywell reserves the right to make changes to improve reliability, function or design. Honeywell does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
U.S. Patents 4,441,072, 4,533,872, 4,569,742, 4,681,812, 4,847,584 and 6,529,114 apply to the technology described
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February 2009
©2009 Honeywell International Inc.
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