Freescale has introduced the thinnest three-axis accelerometer slimming down for consumer sensors

FreescaleSemiconductor Inc. has introduced the thinnest three-axis accelerometer device. By slimming down the MEMS chip to just 0.8mm and adding smart-recognition functions, the company hopes to win design slots in a range of consumer gear.

Freescale has also announced a capacitive touch sensorchip for creating highly inexpensive touchscreens, rotary dials, linear sliders and buttons.

"Freescale has thrown down the gauntlet¡ªits accelerometer is the world's thinnest, and by quite a bit," claimed Marlene Bourne, principal analyst at Bourne Research LLC. "With all the features being built into consumer electronics devices, real estate is getting tight. So if you can create an accelerometer that is smaller and adds functionality¡ªthat is definitely an advantage."

The MMA7450L integrates smart-recognition capabilities for directly reading out linear motion, and Freescale supplies MCU code for rotational- and projectile-motion sensing. The three-axis accelerometer is also Freescale's first MEMS chip to have digital output, offering 10bit resolution with a choice of an I²C or a SPI. That eliminates the need for an ADC, thus saving board space.

"It is very clear that consumer electronics will be the domain of tri-axis accelerometers¡ªyou need that additional sensing capability to expand these devices' functionality," said Bourne. The MMA7450L can sense motion from 1.5g's to 20g's, making it equally suitable for sensing slight hand motions (such as for scrolling the display on a cellphone), detecting vigorous hand motions (such as for gaming) and sensing violent motions, such as motor vibration, pedometer actuation or a fall-related shock to a hard drive.

Tap into new functionality
Also built-in is the ability to recognize single and double taps. Single-tap sensing is useful for such ease-of-use applications as answering a ringing cellphone by merely tapping it anywhere, instead of having to hunt for and depress the proper function key. Double-tap sensing lets designers add functions to consumer gear without adding dedicated buttons for each.

"Music players could use single taps to turn up the volume or, after a double tap, to start turning the volume back down," said Michelle Kelsey, inertial sensor product marketing manager at Freescale.

Freescale is offering $99 paper-clip-sized evaluation boards, along with software for tapping-to-mute, virtual mouse, fallen/shocked hard-disk protection, camera stabilization, image rotation, dead reckoning (for GPSdead zones), e-compass tilt compensation, pedometer functionality, cellphone motion dialing and menu navigation/scrolling.

Touchscreens, pads
Freescale's MPR081/2 proximity capacitive-sensing chips let consumer device makers create touchscreens, panels and pads inexpensively. By connecting metallic traces to the MPR081/2, designers can enable fingertip pressure sensing for consumer gear or fluid-level or frost detection in autos or white goods.

"Touch sensing is becoming ubiquitous in consumer devices, such as in Apple's iPhone, which uses a tri-axis accelerometer to sense screen orientation and capacitive sensing for its touchscreen," said Bourne.

The MPR081 is specialized for rotational controllers, such as virtual knobs. The MPR082 can sense as many as 20 pads for virtual buttons or sliders. Together, the chips let designers create complete control panels without using mechanical switches.

"Designers can hide buttons underneath a surface and morph the touchpad depending on the mode," said Dan Larson, proximity sensor product line manager at Freescale.

Samples of the MPR081 are now available, with volume production slated for October.