The best-known MEMS (micro-electro-mechanical systems) applications in smartphones are the accelerometers and gyroscopes. But there is a lot more to MEMS in today's smartphones than motion sensing. As usual, we'll dig into the guts behind the touchscreen to see what features are delivered by MEMS.


Image courtesy of Yole Développement

 

Despite a decline in the overall IC industry last year, MEMS enjoyed 10 % growth to reach $11B. The latest market report from Yole predicts MEMS devices will reach $22.5B by 2018. And the big market driver for MEMS is mobile computing.

 

Motion Sensing
The use of touchscreens for gaming has popularized motion detection within the portable computing platform. MEMS solutions play a central role including landscape-to-portrait rotation, dead-reckoning navigation, and blasting space aliens.

What was once a two-chip solution with an accelerometer plus a gyroscope now typically integrates three axes of linear motion from an accelerometer with three rotational axes of the gyroscope into a single IC as with the Invensense MPU-6050 in the Nexus 4.

 


Image courtesy iFixit

 

 

Bulk acoustic wave filters
Bulk acoustic wave (BAW) filters saved three-quarters of the board space required by the surface acoustic wave (SAW) filters that had been the mainstay of cell phone antenna duplexers before 2005 when Agilent introduced its FBAR devices.

The BAW devices differ from most other MEMS chips in that there are no moving parts. However, the devices share many of the manufacturing processes and concepts, and market analysts put them in the MEMS bucket.

 

Optical Image Stabilization
Nokia Lumia 920 uses optical image stabilization (OIS). The lens is moved with a traditional voice coil motor used for autofocus. A three-axis gyroscope (purported to be produced by STMicroelectronics) integrated into the camera module detects phone movement and a controller provides feedback to the autofocus mechanism to compensate for the motion.

The concept is very similar to high-end in-lens stabilization in digital SLRs although in a much smaller and cheaper package.

 

Projection Displays
As far back as the first digital projectors in theaters, MEMS have held an important spot in projection displays. The Texas Instruments DLP® (digital light processor) chips used micro-mirrors to steer light for image projection. The TI beam steering approach offered many advantages that allowed the technology to capture markets starting at the high, to office projectors, home theater and finally in portable devices.

Not every smartphone today contains a pico projector, but Samsung has marketed several generations with the chips now seeing service in the Galaxy line in the Samsung Galaxy Beam.

 

Voice Input
Pico projectors and OIS are less common, but there is another MEMS device ubiquitous in the portable market – at least for anything offering voice input. MEMS microphones have completely taken over the market for small form factor products since the MEMS solution is far smaller than any other competitor. Knowles is a leader in the area.

 

And more to come
There are other devices like the digital compass I just can't cover in one post. Some market analysts suggest smartphones could contain upwards of 30 MEMS components in the not-too-distant future.

MEMS have come a long way from the early days as a tire pressure sensor device. Ironically, this is another potential application in the smartphone and could be rolled out as an aid to indoor navigation or as an enabler for better weather apps.

The MEMS market is booming and fuelled in no small part by smartphone deployment of multiple chips for various sensor and actuator applications. Apple alone purchased over $700M of MEMS chips last year according to IHS iSuppli.

 

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