PORTLAND, Ore.—STMicroelectronics NV claims to have extended the battery life of mobile devices with e-compasses with its a new MEMS that combines an three-axis accelerometer and a three-axis magnetometer in a single package. The new six-axis MEMS chip is claimed to cut power by 50 percent while boosting magnetic sensitivity by 30 percent.
The global demand for e-compasses will grow from $1.1 billion in 2010 to $1.9 billion by 2015, according to IHS iSuppli (El Segundo, Calif.). Most e-compasses are based on Hall-effect devices, but STMicro claims that its approach is lower power and less expensive to mass produce, resulting in lower power and increased sensitivity at a price of under $2.
According to STMicro (Geneva), its improved magnetic sensor eliminates the need for flux concentrators used by the more commonplace Hall-effect sensors offered by other e-compass chip makers. Instead, STMicro has made z-axis sensitivity equal to the sensitivity of the x- and y-axes, thereby eliminating the main source of measurement error in e-compasses in the presence of metal in buildings, automobiles, and other urban interference sources, as well as at higher latitudes which can throw off the Hall-effect, according to STMicro.
The super low-power six-axis MEMS chip measures five millimeters square and one millimeter thick and houses both a three-axis accelerometer and a three-axis magnetometer, all consuming about 360 microAmps. Boasting stability over both time and temperature changes, the LSM303DLM is pin-compatible with previous models for drop-in replacement.
STMicro says its six-axis e-compass employs MEMS to cut power in half and boost magnetic resolution by a third.
e-compasses face an interesting technical issue - they are typically a "nice to have" feature of a device. The user is not willing to accept a big hit in performance for the added functionality provided. This presents a particular engineering challenge to the designers to minimize the size and power requirements. If they are successful, the added capabilities make it possible to delight the user - as the iPhone often does.
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