STMicroelectronics has integrated a 3-axis digital accelerometer with a 3-axis digital magnetic sensor in a single module. The digital compass module uses magneto-resistive technology from Honeywell and aims to accelerate the adoption of enhanced electronic compassing in portable consumer applications, including direction finding, map/display orientation, location-based services and pedestrian dead reckoning.
The module adds forward direction orientation that enables application developers to improve the use of limited phone/PDA display size for maps by putting the current user position at the bottom of the map with the rest of the display in the forward ('up ahead') direction. The compass provides accurate heading information, to indicate the direction in which a person or vehicle is moving, when GPS is not available. It also supports dead-reckoning applications, including pedestrian navigation in places with no or low GPS signal, such as inside buildings and structures or in mountainous and forested terrain. Compass modules in handsets open new possibilities for advanced location-based services.
With compassing and GPS capabilities, consumers will be able to identify and retrieve information on nearby points of interest, such as restaurants or shops, by simply pointing their mobile devices in the direction of the object concerned. High-precision sensing couples with smart embedded features, including wake-up/power-down function and 6D recognition, which signals if the device is up or down along all three axes (x,y,z). The device has a linear acceleration full-scale of ±2/±4/±8g and a magnetic field full-scale from ±1.3 up to ±8 gauss(2), both fully selectable by the user.
The magnetic sensing element that measures the strength and direction of the Earth's magnetic field and determines the heading relative to magnetic north is based on Honeywell's Anisotropic Magneto-Resistive (AMR) technology. This technology combines best-in-class accuracy in compass calculations with low power consumption, which is crucial in battery-hungry portable devices. The AMR technology provides the same sensitivity on the z axis as it does on the x and y axes, eliminating the need for flux concentrators used in Hall-effect type sensors that can shift the sensor offset after it has been magnetized.
This market-unique three-axis sensing approach reduces measurement errors in ultra-low magnetic field strength environments, such as in metal buildings, automobiles, or in higher latitudes like Canada or Northern Europe. Moreover, Honeywell's magnetic sensor design includes a built-in offset cancellation circuit to minimize the need for calibration, and patented set/reset straps that de-gauss, or de-magnetize, the sensor for each measurement to improve accuracy.
According to iSuppli, the market for MEMS digital compasses for use in mobile phone applications alone will grow from 8 million units in 2008 to 540 million units in 2013 - a CAGR of 129%. During the same time period, revenues for these components will grow at a CAGR of 110%, from $8 million to $325 million.
ST's LSM303DLH digital compass module fits in an eco-friendly package of 5x5x1 mm and it is software- and register-compatible with ST's three-axis digital accelerometer family (LIS331DLH/M/F). Samples are available and the device is ready for mass production. Unit pricing is $2.5 for volumes in the range of 50,000 pieces.
