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Capacitive touchscreen tech battle heats up

Posted: 10 Sep 2009 ?? ?Print Version ?Bookmark and Share

Keywords:capacitive touchscreen? resistive technology? smart phone? interface? LCD?

Multi-touch attraction
Multi-touch is already becoming all the rage among touchscreen vendors because touchscreens todaybeyond a simple pinch or swipe gestureget easily confused by erroneous "ghost" responses. It's critical for a touchscreen to distinguish between a finger touching the screen and contact with an ear or cheek when the display is on a mobile phone.

Advancements of capacitive technology, coupled with smarter software algorithms running on touchscreen processors, are now imminent.

Cypress' TrueTouch technology can handle up to 10 simultaneous inputs. The mTouch solution from Microchip Technology has up to 16 inputs and IDT's PureTouch features 15 inputs, according to Databeans.

Atmel's maXTouch technology, in theory, is capable of unlimited touches. Its first product, mXT224, provides support for 10 fingers on a 4.5-inch screen. "It sees all 10 fingers separately, capable of tracking and tracing them," according to Atmel's Carey.

When a touchscreen gets more information of "touch" and "press," including x-y locations of fingers and z coordinates, its chip can run post-processing algorithms to produce more accurate touch information.

For example, Atmel has developed in-house a host of algorithms including "grip suppression," all designed to run on their chip. The algorithm, whose intellectual property is owned by Atmel, can reject and continue to track five finger touches used to hold a touchscreen smart phone, said Carey.

Stylus support
Where capacitive touchscreen technology typically fails, though, is in lack of support for cost-effective, passive, thin stylus or fingernails. This is because capacitive touchscreens have problems with a touch that does not register contact with an insulator material, like fingernails or stylus tools, explained Inouye.

She said, "What is cool about the Atmel's solution is that it addresses the problem of capacitive touchscreens." Inouye sees the support for fingernails and no electronic thin stylus as the most compelling benefit to the maXTouch solution from Atmel."

Some consumers claim that nothing beats a smart phone with a touchscreen and a stylus for serious on-the-road productivity. If true, Atmel is seeking that sweet spot with its new maXTouch.

Enabled by its 80:1 SNR and extremely fast refresh rate, Atmel claims that its maXTouch is the first capacitive touchscreen solution supporting the use of a stylus for drawing or signature capture and character recognition.

A high SNR is crucial to accurately report adjacent or weak signals. It also enables precise reporting in noisy environments such as products with noise coupled from radio transceivers, LCD displays and battery chargers, said Atmel.

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