MEMS accelerometer sports smart algorithms

PORTLAND, Ore. — As the market for MEMS-based accelerometers shifts from automotive and industrial segments to consumer devices, Freescale Semiconductor Inc. claims it has become one of the top three MEMS suppliers.

Freescale (Austin, Texas) said it is focusing on lower power, less expensive three-axis accelerometers that incorporate built-in algorithms capable of sensing taps, shakes and all six possible orientations.

Global revenue for MEMS devices in cellphones will increase to $1.3 billion by the end of 2012, up from $299 million in 2007, according to market watcher iSuppli Corp. Accelerometer adoption in cellphones is forecast to grow from $220 million in 2009 to $426 million in 2010. Growth is expected to be driven by the adoption of accelerometers in consumer devices with user interfaces that harness smart algorithms built into MEMS sensors, according to iSuppli.

Michele Kelsey, marketing manager for inertial sensors at Freescale, said its MMA7660FC device also has three power modes, along with eight power-select options, “that allow devices to draw the minimum amount of power necessary for specific applications.”

Consumer devices can now harness the built-in intelligence in an accelerometer that allow users to control its functions, including automatically switching from portrait to landscape orientations. Smart algorithms built into the latest accelerometers permit more advanced functions without having to press key combinations or shake a phone to activate different functions.

By combining the accelerometer's ability to provide interrupt-driven responses that sense taps and shakes in all six orientations, consumer, medical and other electronics can be upgraded with a variety of intelligent functions that do not burden the host processor. For instance, a double-tap on an upright touch screen device could activate a drop-down menu bar to save screen space without requiring an extra button to be polled by the processor.

Power modes in Freescale's three-axis accelerometer are said to consume less than a 0.5 microamps in the “off” and 2 microamps in “stand-by” mode, respectively. They are complemented with eight configurable sample rates for active mode that can be used to optimize power consumption for specific applications.

Freescale claims its accelerometer can survive up to 10,000 Gs of shock, and communicates directly with the main system processor through an I2C interface. The chip is supported by two development system boards: one with standard connectors for use with Freescale's development system software ($119) and a daughter board using a DIP connector that allows the accelerometer to be unplugged from the development board and plugged into a manufacturer's own prototyping board ($35).

The MMA7660FC chip is available now in a 3- by 3- by 0.9-millimeter package for $1.39 in quantities of 10,000.

Freescale said it is targeting the MMA7660FC accelerometer for portable consumer devices such as mobile phones, PDAs and digital cameras as well as for medical and gaming applications.

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