STM electronic compass improves accuracy for fitness trackers
May 17, 2016
Fitness trackers, other wearables and smartphones could get better at guiding users and mapping their sporting achievements even where satellite navigation cannot work, using an electronic compass from ST Microelectronics.
Fitness-tracking smartphone apps, smartwatches and bands need continuous location data for mapping and recording, and accuracy is critical for wearers who like to monitor their progress and share achievements online. A built-in e-compass helps calculate location when satellite signals are unavailable, such as inside buildings or when running or cycling under tree cover. However, these can give errors of about 10Ëš in latitudes such as northern Italy or northern California. This can put the user off course by 150m or more in every 1km travelled.
STM’s LSM303AGR e-compass is claimed to cut the heading error to less than 4Ëš, using the Swiss company’s proprietary technology for manufacturing high-accuracy magnetic sensors. This enhanced accuracy combined with low-power operation makes it suitable for high-precision pedestrian dead reckoning (PDR) on mobile devices.
The device also enhances dead-reckoning accuracy in applications such as automotive navigation, and maintains accuracy over the full temperature range from -40 to +85ËšC.
“The industry-leading technology behind STM’s new e-compass further extends our lead in MEMS sensing for positioning and motion detection in consumer devices,” said Andrea Onetti, group vice president at ST Microelectronics. “High-precision PDR, enabled by this device, will significantly enhance the user experience delivered by apps including fitness trackers and personal navigation on smartphones and devices like smart watches, which IHS predicts will exceed 100 million units by 2020.”
The e-compass is available now, packaged as a 2 by 2 by 1mm 12-lead LGA package.
As an all-in-one e-compass IC fabricated on a single die, the device combines a three-axis MEMS accelerometer using the company’s Thelma (thick epi-poly layer for microactuators and accelerometers) technology and a compact three-axis anisotropic magneto-resistive (AMR) sensor that delivers higher sensitivity and lower noise than conventional Hall sensors.
The AMR manufacturing process technology gives the device temperature stability compared with using giant magneto-resistive (GMR) or tunnel magneto-resistive (TMR) technology. The AMR sensor also has high dynamic range, which contributes to the device’s accuracy by preventing magnetic saturation in areas of high ambient-field strength.
Magnetic-sensing accuracy has been field tested at various latitudes and the company claims it did better than current e-compass ICs and pure magnetic sensors.