Honeywell HMC6052 is a 2-axis magnetoresistive sensor plus amplifier and analog support functions compass and low magnetic field sensing. The product is available in a 14-pin surface mount 3.5mm x 3.5mm LCC package. A set of two-channel amplified sensor signal switch functions allow compass system designers a compact, easy-to-implement solution. Application HMC6052 includes electronic compass and magnetometer. Honeywell continues to maintain product excellence and introduce innovative solid state magnetic material sensor solutions. They are very reliable, top-notch performance what they promise to deliver. Honeywell magnetic sensor products provide real solutions you can rely on.

Features and Benefits

4 2-axis AMR magnetic sensor (HMC1052) with integrated amplifier and setting circuit

4 complete analog solutions, optimized for the compass. Eliminates need for external amplifiers and 4 single dies in most discrete surface mount packages (3.5 x 3.5 x 0.8mm 14-pin LCC)

4 Optimized for minimal footprint and easy integration

4 minimum support components 4 only two capacitors for analog signal processing

4 Field of view range +/- 2 Gauss 4, optimized for handheld or hard iron compass applications

surroundings

4 Low voltage operation (2.5 to 3.6 V) 4 Compatible with battery powered applications

4 Precision Magnetic Field Measurements 4 User ADC Resolution Limits Output Accuracy

4 Minimum detectable magnetic field (80 microGauss) 4 Allows accurate compass and magnetic field measurements

4 Lead-free packaging structure 4 Compliant with current environmental standards (RoHS)

Installation Precautions

Stencil Design and Solder Paste

A 4-mil stencil and electrical contact pads with 100% adhesive coverage are recommended. The HMC6052 has been tested successfully without clean solder paste. Pick and place placement is machine dependent, no restrictions are recommended, and has been tested for mechanical centering. The placement force should be equivalent to a 1206 SMT assembly.

Reflow and Rework

The HMC6052 requires no special outline and is reflow compatible with lead eutectic and lead-free solder pastes. Honeywell recommends following the solder paste manufacturer's guidelines. Should irons with tip temperatures be used at temperatures greater than 315°C.

Application Notes

The HMC6052 integrated compass sensor circuit consists of two magnetoresistive (MR) sensors that sense an external magnetic field for the electronic compass function and additional analog support circuitry. Two instrumentation amplifiers follow the sensor Wheatstone bridge to measure the differential output signal and provide substantial voltage amplification. A voltage reference is used to center the amplifier for a common zero-field bias point. A pair of electronic includes switching circuits that use external capacitors connected to the SC- and SC+ pins to create the set pulse function. In the quiescent state, the capacitor will be charged to the full supply voltage and then suddenly discharged in reverse polarity when the SINL and SINH pins flip the logic state. The resulting set pulse current flows through the set sensor bridge to recalibrate the magnetic moment on the bridge's magnetoresistive elements. This set of switching strip circuits is based on user requirements, or periodically to eliminate any potential magnetic interference from the sensor.

The schematic in Figure 1 shows the basic HMC6052 application circuit with minimal external components.

In Figure 1, the host microprocessor (µP) controls the HMC6052 through digital output port lines DO0 to DO2. This first digital control line (DO0) is normally at a high logic state and is briefly pulled down to drive the connected high side switch to pin 10 (SINH) of the HMC6052. Likewise, DO1 is an inverted logic control line that is normally low and briefly pulled high to drive the low-side switch at pin 7 (SINL) of the HMC6052. DO0 and DO1 toggle states together to create a "set" pulse through the sensor bridge element's spiral-shaped internal fixed-band resistor. This set pulse creates a strong magnetic field churning that rearranges the magnetic domains of the magnetoresistive element to eliminate thermal effects, as well as any magnetic disturbance events that might "interfere" with the sensor. The frequency of switching is the designer's choice, but typically ranges from once per second to once per day. An externally set band capacitor (SC-) 9 (SC+) across pin 5 has a value between 0.2uf and 1uf, the point is to keep the total capacitance ESR (effective series resistance) less than 0.5 ohms to reduce internal capacitor losses while providing Current peak amperes exceeding 0.5.

The microprocessor also controls all power supplied to the HMC6052 via the digital control line DO2

Switch the MMBT2907 bipolar junction transistor to connect the 3.0V system supply voltage to the sensor circuit. By pulling DO2 low, the transistor saturates, connecting Vdd to Vdd, which is the switching power supply connected to the V supply (pin 11) and the V bridge (pin 3). Under power-on conditions, the HMC6052 internal circuitry can quickly and stably provide accurate magnetic vector voltages at output pins 13 (OUTA) and 14 (OUTB). With a near-zero magnetic field input, the OUTA output voltage should be close to half the supply voltage to provide a bipolar output voltage value corresponding to the strength and polarity of the magnetic field generated on the sensor bridge. Zero-field excitation of the HMC6052 can be obtained using a magnetically shielded container or a Helmholtz coil set.

In many applications, switching the DO2 digital control line is necessary to reduce the overall current consumption of the system when not taking magnetic field measurements to preserve battery energy reserves. available from the power supply during sensor circuit operation. Take a "snapshot" measurement through the "duty cycle" DO2 and during sensor on. For example, a 3.0-volt lithium meter battery might have a typical 150mAh energy capacity rating. Reference design drawings about 15mA continuous operation, only 10 hours of operation results. By placing the microcontroller and the HMC6052 in sleep mode 99% of the time, the total battery life is extended to 1000 hours. Better efficiency could be if the host microprocessor only toggles on DO2 for a few milliseconds, it can do the analog-to-digital conversion output OUTAOUTB, then pull DO2 high to sleep the HMC6052 until the next required measurement update.

The analog outputs of the HMC6052 circuit (OUTA, OUTB) are representative voltages proportional to the magnetic field across sensor bridges A and B. The sensor bridge has an orthogonal axis of sensitivity and creates two dimensions. Representation of magnetic field strength and direction. When the direction is close to the ground, the output can then be used for an electronic compass by sensing the horizontal component of the Earth's magnetic field. Using an on-board analog-to-digital converter within the host microprocessor, the number of North Pole representing the magnetic field direction can be correlated to the host platform (watch, phone, PDA, vehicle, ship, airplane, etc.). The output of the HMC6052 is referenced to approximately half the supply voltage applied on pin 11. (VSUPPLY) and 12 (GND). Without considering other errors, OUTA (pin 13) and OUTB (pin 14) will be close to 1.5 volts, no magnetic field applied (completely shielded), and a supply voltage of 3 volts. If the shield is removed and a nominal earth magnetic field of 300 milliGauss and -100 milliGauss is applied across sensor bridges a and B, OUTA starts moving positively from 1.5 volts and OUTB starts moving negatively from 1.5 volts. Neglecting offset error and using a nominal sensitivity of 0.5 volts per gauss, OUTA will be around 1.65 volts and OUTB will be around 1.45 volts.

Using the example values of Earth's magnetic field excitation above, a host microprocessor with a 10-bit ADC can provide 1024 increments (or counts) through a nominal zero to 3 volt supply voltage. If you reference count 512 (about 1.5 volts) as the zero Gauss point, the 1.65 volt and 1.45 volt output A and output B levels translate to counts 563 and 495, respectively. Without compensating for offset errors and calibration coefficients, the magnetic vectors for outputs A and B would be 51 – 17 counts relative to zero field level counts. In an electronic compass, the arc cut (B/A) is performed by the microprocessor, resulting in a heading of approximately 341 degrees (magnetic northwest 19 degrees).