HMC6352 Datasheet, PDF (10/13 Pages) Honeywell Solid State Electronics Center – Digital Compass Solution

HMC6352
Example 5: The final example shows how to read RAM register 7F(hex). First perform a write operation to command the
HMC6352 to read a RAM register and define which register to read (Example 3). The sensor puts the answer in the data
buffer. Then perform a read operation to clock out the answer (Example 1). There is a Stop/Start event in between the
write operation and the read operation. This example is just a combination of Examples 3 and 1, but it is provided to show
that reading a register involves both a write and a read operation.
STOP
START
SDA
SCL
M_SDA
S_SDA
42(hex)
“g”
Write to This I2C Address _Command
Application Notes
7F(hex)
Register 7F
43(hex)
Read From This
I2C Address
55(hex)
Data
The HMC6352 Integrated Compass Sensor circuit is composed of two magneto-resistive (MR) sensors with orthogonal
orientation for sensing the horizontal components of the earth’s magnetic field (0 to 630 milli-gauss), plus two amplifiers, a
set/reset drive circuit, and a microprocessor (µP). Best accuracy is obtained in clean magnetic environments (free air) and
held level, or perpendicular to the gravitational direction. At worst case, each degree of tilt from a level orientation could
add two degrees of compass heading error. Magnetic errors can be introduced if operated near strong magnetic sources
such as microphone or speaker magnets, transformers in test equipment, and CRT deflection yokes in video
displays/monitors. These magnetic errors can typically be reduced or eliminated by performing the calibration routine.
When locating the HMC6352 in dense printed circuit board designs, take precautions in location of this magnetic field
sensing device for soft-iron effects that bend the earth’s magnetic field. These soft-iron effects are from ferrous materials
without residual magnetization and tend to be items like nickel-plating on SMT component contacts and RFI/EMI shielding
materials. The amount of stand-off of the HMC6352 from these soft-irons is heuristic and dependant on the amount of
material, material shape, and proximity.
A user calibration mode is available in the HMC6352 to diminish hard-iron effects of the end-user’s (customer’s) location
of the product. Hard-iron effects come from nearby ferrous materials with residual magnetism that buck or boost the
intensity of the earth’s magnetic field, leading to heading errors. Such hard-iron effects come from vehicle chassis,
speaker magnets, and high current conductors or circuit traces.
PCB Pad Definition
(Dimensions in Millimeters)
The HMC6352 is a fine pitch LCC package with a 0.80mm pin pitch (spacing), with the pin pads defined as 0.70mm by
0.33mm in size. PCB pads are recommended to be oversized by 0.025mm from each pad for a short dimension oversize
of 0.05mm. The interior PCB pad is recommended to be 0.05mm oversized per pin with an exterior oversize of 0.20mm
for proper package centering and to permit test probing. Lead finish is SnAgCu.
Soldering attachment shall be done by SMT lead-free reflow methods with standard preheating, soaking, reflow, and
cooling profiles for large body parts. Caution, excessive temperature exposure beyond the profiles may result in internal
damage to the HMC6352 circuits.
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