MEMs在手机中的应用，看来是一个趋势啊，讨论一下！

eyeinwind

Mass market makes a MEMS move


R. Colin Johnson
(11/20/2007 11:32 H EST)
URL: http://www.eetimes.com/showArticle.jhtml?articleID=204200313

PORTLAND, Ore. -- Micro-electro-mechanical systems (MEMS) penetrated the mass market two decades ago, when they enabled air bags to trigger fast enough to catch passengers before they hit the steering wheel or windshield. MEMS chips gained a major business-market design-win a decade ago, when they began to be used to fabricate the high-precision ink-jet print-heads that displaced impact printers.
Now, MEMS chips are entering the consumer-electronics mainstream with the same invigorating effect. Most recently, we're seeing MEMS technology being used in Nintendo's Wii and Apple's iPhone, and this may just be the beginning. The real volume customers will be the mainstream consumer-electronics makers adding MEMS chips to their ubiquitous devices. "We are at the edge of a mass market--today's MEMS applications are just the early adopters," said Bosch-Sensortec general manager and chief executive officer Frank Melzer. "The true mass-market adoption of MEMS will come when designers understand how a single MEMS sensor can have multiple uses in a single device, and when they learn how to use multiple sensors together to solve tough problems."
Bosch-Sensortec is the CE division of Robert Bosch GmbH, the world's largest MEMS chip maker, which spun off its consumer electronics division in 2005. Now, Bosch-Sensortec has seven MEMS chips available for consumer applications--two pressure sensors for altimeters and navigation; two gyroscopes for image-stabilization applications; and three accelerometers, including a second-generation three-axis unit, the SMB380, which was recently dissected by Chipworks (Ottawa, Canada).
"Bosch's decision to spin-out its Sensortec division, dedicated to consumer electronics, appears to be paying off," said St. John Dixon-Warren, head of Chipworks Technical Intelligence Process Engineering team. "When we opened their new digital accelerometer, the SMD380, we found the MEMS die next to the ASIC instead of on top of it like before--that's how they made it thinner, which is what consumer devices need. Plus, Bosch has shrunk both the MEMS die and the ASIC, which is also what they needed to do to meet price concessions to mass-market customers while still making a profit."
Together with its parent company Robert Bosch, Bosch-Sensortec had MEMS sales in excess of $370 million last year--more than any other MEMS chip maker, according to Wicht Technologie Consulting (WTC). STMicroelectronics and Freescale Semiconductor ranked second and third in WTC's ranking. Bosch intends to keep its lead, too; for instance, it just invested in a new 8-inch fab in Reutlingen, Germany, where up to thousand wafers containing up to one million chips per day will start being produced by 2009.
The consumer-device makers buying all those chips, according to Melzer, are telling Bosch-Sensortec that they want reference designs showing how to utilize MEMS chips in multiple ways. For instance, cell phones are predicted to consume as many as 10 billion MEMS chips by 2010, according to Philippe Kahn, founder of Fullpower Technologies Inc. (Santa Cruz, Calif.). Cell phones will use accelerometers to perform user-interface duties, such as picking-up the phone by shaking it, as well as to perform secondary tasks, such as extending battery life with intelligent power management that turns off the cell phone's display when its laid face down.
Beyond using a single MEMS chip for multiple tasks is using multiple sensor chips for a single task. Here, STMicroelectronics agrees with Bosch-Sensortec, according to Jay Esfandyari, MEMS market development manager at STMicroelectronics. As an example, Esfandyari has recently been demonstrating a reference design for an electronic compass that compensates for tilt using a three-axis accelerometer. Normally, a magnetometer chip requires that you keep it flat to read-out a compass heading correctly, but an accelerometer can sense orientation and compensate. STMicroelectronics' reference design shows the compensating compass heading in bold, with a lighter indicator showing how much the compass would be off if it wasn't equipped with the accelerometer.
Bosch-Sensortec is currently putting together another multi-mode reference design that points the way for OEMS using its chips for next-generation consumer-electronic devices. In particular, Bosch-Sensortec is working with the navigational device maker NumeriX S.A. (Manno, Switzerland) to combine a Bosch-Sensortec MEMS barometric-pressure sensor with NumeriX's global-positioning system (GPS) chip set.
"We make the world's smallest digital-pressure sensors, which we are integrating with GPS navigation solutions from NumeriX," said Melzer. "The SMD500 pressure sensor can detect changes in height as small as one foot, which helps when navigating stacked freeways and facilitates timely notification of upcoming exits. A pressure sensor can also help distinguish between closely packed freeway clover-leafs by detecting the slope of the road," said Melzer.
By integrating Bosch's SMD500 barometric pressure sensor with NumeriX GPS chips, the NumeriX/Bosch reference design achieves higher resolution for more accurate "turn" commands, as well as allowing multilevel bridges and stacked highways to be more easily navigated.