Madison, Wis. — The success of the iPod has triggered a user-interface revolution for portable devices. All those itty-bitty buttons, and even the mini-magic wand once favored by most resistive touchscreens, are being replaced by variations on the iPod's popular touch-activated screen, making the approach one of the hottest trends to hit the consumer market.

One of the first companies to capitalize on the new trend is Neonode AB (Stockholm, Sweden). The startup is already selling a mobile phone that features a patented optical touchscreen, using technology based on a grid of infrared light beams that are reflected onto the screen.

Analog Devices Inc. (Norwood, Mass.) is also betting on the touch-activated screen market for mobile devices. ADI today will launch a low-power capacitive sensor, called the AD7142, for MP3 players, mobile phones and digital cameras.

This 16-bit sigma-delta capacitance-to-digital converter provides 14 programmable inputs for a variety of sensor configurations. Features include finger-driven scroll bars, eight-way position sensors and scroll wheels that drive pop-up menus — all intended to make it easier for users to flip through large files of music, pictures and video.

More important, ADI's capacitance-to-digital converter cuts power consumption by 50 percent when compared with competitors' solutions, said Kevin O'Connell, marketing manager for ADI's precision signal-processing business. The sensor's full-power mode — when the finger touches the screen — consumes less than 1 milliamp, while shutdown current is less than 2 µA. When the sensor is still on but the user is not touching the screen, the device consumes less than 50 µA, while competitors' solutions often require twice as much power, the company said. Just as important, when the screen is touched again with the sensor still in that state, competitors' sensors typically respond in about two seconds, while ADI's device responds in 0.4 second, according to O'Connell.

ADI's capacitance sensor can also adjust to rapidly changing temperature and humidity in a mobile environment, which improves the accuracy and reliability of the touch controls, O'Connell added.

Two companies now dominate the computer touch pad market: Japan's Alps Electric and Santa Clara, Calif.-based Synaptics Inc., which designed the iPod's touch pad scroll wheel. With many more tier-one and tier-two consumer electronics companies developing finger-enabled touchscreen systems, there may be room for new players. ADI says it has several design wins in leading-brand-name and tier-two products. The AD7142, which has been sampling since August, is priced at $1.09 in high-volume quantities and will go into mass production in February.

Easy scrolling
Finger-enabled touchscreens offer one major advantage, said Susie Inouye, research director and principal analyst at Databeans Inc. "The value-add with a touch pad is the ability for users to move about a screen or scroll through large listings, such as songs or other files," Inouye said. As storage expands in many consumer portables, the ability to easily scroll through long lists becomes a key issue.

While MP3 players are a growing application for touch pads, Inouye predicted that "new camera designs as well as cell phones may incorporate a touch pad interface in next-generation designs."