05 July 2011
Baolab says it’s on the right heading with digital compass
Baolab Microsystems claims to be the first company to design a pure cmos Lorentz force MEMS sensor, which can detect the Earth's magnetic field. The MEMS structure, constructed using Baolab's NanoEMS process, is a moveable aluminium plate suspended by springs.
NanoEMS enables nanoscale MEMS devices to be built using a standard cmos process and to be integrated monolithically with analogue and digital electronics. The MEMS elements are defined within metal interconnect layers by etching away the intermetal dielectric during the normal cmos production process.
When a current passes through the plate, it experiences a force proportional to the surrounding Earth's magnetic field. The resulting displacement is measured using capacitive detection between the moveable plate and fixed electrodes around it. In this way, one chip can sense the magnetic field in the x, y and z directions.
The first product to use the approach is the company's 3D Digital NanoCompass, which is said to match performance benchmarks for sensitivity, power consumption and package size, but at lower cost. A further benefit is that the device can autocalibrate to maintain consistent accuracy.
Until now, the Lorentz force approach has not been used extensively, due to the cost of manufacture using conventional MEMS techniques. NanoEMS is said to make it possible to make such devices at a fraction of the cost, opening the market for a new generation of mobile devices equipped with the NanoCompass.
Samples of the NanoCompass, which has a 5° heading resolution, will be available in 2012. Providing 13bit per axis, the compass will be available with i2c or spi interfaces and in a 3 x 3 x 0.9mm 10 pin dfn or a 2 x 2 x 0.75mm bga.
Author
Graham Pitcher
Supporting Information
Websites
http://www.baolab.com
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