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ST fields capacitive sensor to simplify user interfaces

Posted: 05 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:capacitive sensor? capacitive sensing technology? touchscreen market?


Triggered by the huge success of the iPod, the user interface is now suiting up to integrate touch control-based designs, shedding off the multiple control buttons in electronic devices to pave way for simple, minimalist surfaces. And with the debut of iPhone, the touchscreen interface is expected to be the next big thing in consumer electronics. Market research firm iSuppli predicts the touchscreen market will hit $4.4 billion by 2012, prompting companies to aggressively capitalize on this segment.

On its way to make room for itself in the already maturing market is STMicroelectronics. The company launched last month the QST108, its first device under its QST portfolio of touch sensors.

Explaining their move into the arena, Eric Payet, 8bit marketing manager, MCD marketing at ST said, "Touch-sensitive control is becoming more and more popular to replace electromechanical switches in devices. Not only that, the device also allows the designer to develop more attractive and more elegant user interfaces."

"We see this [technology] spurring a lot of interest from companies in different segments. And we see a lot of projects on-going to implement this technology in the human and machine interface," he added.

Interface evolution
ST's QST108 capacitive sense device enables the development of touch interfaces with eight-key configuration. It implements QProx capacitive technology to provide an intelligent single-chip control interface that responds to a user's touch thus, providing what ST claims to be the most adaptive solution today in its device class.

"The device integrates a pure digital, firmware-based technology," said Payet. "That means you can easily adopt from firmware to specific customer needs, enabling us to also develop QST customer-specific versions and produce them in big volume. So, the device is very flexible, compared to competitor solutions, of which some use analog implementation." He also noted that the device enables significant reduction in touch panel cost.

The $1.80 device incorporates Quantum's Advanced Key Suppression (AKS) technology that offers adjacent "touched key" determination mechanism. This function addresses interface usability such that when two or more keys are touched simultaneously, the device will detect the key with the highest capacitance field and eliminate the key with the lower capacitance field thus, decreasing input inaccuracy. Other advanced processing techniques include drift compensation, auto calibration and noise filtering.

In terms of design, the chip also features a 1.8V operating voltage and microwatt operation for battery-powered applications, thus addressing low power issues. The device also allows all kinds of construction methods including backlighting capability, curved interfaces and thin or thick panels to permit different designs.

ST's QST108 capacitive sense device enables the development of touch interfaces with eight-key configuration.

Though not the first device with the mix-and-match configuration of buttons, wheels and sliders, Payet said that their QST devices can implement the slider from the wheel with configurable evolutionthat is, designers can implement one rotation of the wheel in one, two, four or 128 steps as desired.

According to Payet, the QST device incorporates a robust and very reliable technology, making it extremely tolerant to environmental changes and lessening damage due to factors such as humidity, moisture and temperature.

Hot apps
With its functionality, Payet pointed out several key applications for ST's new device.

"I would say that the biggest potential segment is the mobile phone market. You can see major companies like Motorola, Samsung and Nokia integrating the technology," Payet explained.

Aside from mobile phones, Payet added that touchscreen sensors are targeted at other digital consumer and home multimedia devices such as portable multimedia gadgets, STBs, DTVs, DVDs, digital audio, remote controls and gaming consoles. He added that they also see potential for the technology extending into the home appliances segment, particularly in white goods such as washing machines, dishwashers and microwave ovens.

In the computing arena, Payet said that ST eyes applications in computer peripherals such as mouse, keyboards and monitors.

The device also suits automotive apps such as car radio, car multimedia and telematics. According to Payet, the capacitive sensor can function for proximity detection, such that it can be used to set the light on as your hand approaches the dashboard.

Payet also singled out medical systems as an emerging market for capacitive sensing technology that promises low power consumption and simple interface. He said ST is engaged with companies involved in the development of applications such as glucose meters and blood pressure meters.

ST is designing the QST device in France and is tapping its U.S. wafer fab for production. For backend and packaging operations, the company is using its facility in Malaysia and its warehouses in Singapore. The core R&D team for the device is based in France and they are also engaged in key competency programs with customers in the areas of mobile communication, PC peripherals, consumer and home appliances. Currently, ST is working with local companies in Shanghai, China and Korea to develop custom-specific QST-based solutions.

2H plans
Later this year, ST will introduce four additional products in their QST line-up. These include the 8-pin QST101 and QST102 devices, which feature one- and two-key configurations, respectively. One- or two-key designs see big potential for on/off control in electronic devices such as rice cookers.

Upcoming solutions also include 16-pin QST104 four-key touch panel solution and the 32-pin, I?C compliant QST1610 that offers one wheel and seven key touch panel designs. Payet said that the rotary wheel in the QST1610 is similar to the iPod, of which up to seven keys can be designed around it for mobile phone apps.

"There is a trend for simple-key configuration for mobile phones and we are preparing to address this trend by offering these simple-key solutions," noted Payet.

The devices will ship to OEM customers first and will be released for mass market in Q4. The company is also working on five devices that are slated for introduction in 2008.

- Anna Valmero
EE Times-Asia

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