Freescale Semiconductor Inc. today will unveil the thinnest three-axis accelerometer devised to date at the Sensors Expo & Conference in Chicago. By slimming down the microelectromechanical-system (MEMS) chip to just 0.8 mm and adding smart recognition functions, Freescale (Austin, Texas) hopes to win design slots in a range of consumer gear.
Freescale will also announce a capacitive touch sensor chip for creating highly inexpensive touchscreens, rotary dials, linear sliders and buttons.
"Freescale has thrown down the gauntlet--its accelerometer really is the world's thinnest, and by quite a bit," said Marlene Bourne, principal analyst at Bourne Research LLC (Scottsdale, Ariz.). "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, that is definitely an advantage."
The MMA7450L integrates smart recognition capabilities for directly reading out linear motion, and Freescale supplies microcontroller code for rotational- and projectile-motion sensing. The three-axis accelerometer is also Freescale's first MEMS chip to have digital output, offering 10-bit resolution with a choice of an I2C or aserial peripheral interface. That eliminates the need for an analog-to-digital converter, thereby saving board space.
"It is very clear that consumer electronics will be the domain of tri-axis accelerometers--you need that additional sensing capability to expand these devices' functionality," said Bourne. The MMA7450L can sense motion from 1.5 g's to 20 g's, making it equally suitable for sensing slight hand motions (such as for scrolling the display on a cell phone), 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.
Tapping 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 cell phone 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 GPS dead zones), e-compass tilt compensation, pedometer functionality, cell phone motion dialing and menu navigation/scrolling.
Touchscreens and 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 available this month, with volume production slated for October. The MPR082 will be about three months behind.