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Touch controller runs on all-digital process

Posted: 25 Feb 2009 ?? ?Print Version ?Bookmark and Share

Keywords:touch sensor? controller? digital process? analog process?


Fujitsu Microelectronics America Inc. (FMA) has begun distribution of a compact, flexible touch sensor controller from ATLab Inc. of South Korea. The FMA1127 controller converts capacitance generated by the human body and conductive touch pad to digital data with no analog processing.

This low-power, fast-processing, easy-to-implement capacitive touch controller is suited for cellphones, PDAs, remote controllers, multimedia players and other mobile devices. Digital touch sensor technology allows for easy, multi-touch, intuitive access and navigation. The controller is water resistant and can be implemented with a variety of materials, making the FMA1127 a suitable design choice for alarm systems, handheld health care products and home appliances, or for other applications where the controller can replace mechanical switches and buttons.

The FMA1127 is manufactured by FMA at its Aizu-Wakamatsu facility in Japan using 0.25? technology. The controller was developed to compare reference and sensor input impedances to detect touchall in the digital domain. The original touch sensor controller technology was targeted to replace conventional buttons, and has now been applied to touchscreens and proximity sensors using ATLab's DigiSensor, which measures imbalances in impedance caused by finger contact. Compared with most keypads in cellphones, the touch sensor controller's DigiSensor enables thinner, lighter portable electronics products.

Thin, light, flexible digital contact
The FMA1127 operates at a wide voltage range of 2.5V to 5.5V, and at temperatures between -35C and 85C. Current requirements are less than 0.15mA, and response time is only 0.2ms. A total of 8kV ESD protection is provided for the chip/contact pad and 15 kV for system/air. No ground is required for the touch pad, and no external clock source is needed. Equipped with an I?C interface, the FMA1127 automatically adjusts sensor sensitivity based on the operating environment. The controller includes Automatic Impedance Calibration (AIC), which supports various sensitivities for individual channels independently, and is used to change calibration intervals and other parameters. AIC can be paused and resumed using a microcontroller.

The FMA1127 also includes ATLab's Adjacent Pattern Interference Suppression filtering function to eliminate adjacent key or pattern interference. The FMA1127 touch sensor controller provides both touch-strength output and touch on/off output. Two types of interruptsgeneral-purpose and touch detectionare available. Resolution of touch strength is 8bits (256 steps).

Several general-purpose DIOs also are incorporated in the controller, depending on the package type. These can be configured and programmed to meet specific customer needs, providing additional flexibility and value.

"The FMA1127 represents a significant breakthrough in human input devices, enabling lighter and smaller mobile devices that use all-digital processing for access and navigationat a very competitive price point," said Dean Chang, senior product marketing manager at FMA. "This touch sensor controller is very environmentally friendly, power efficient, and can be easily integrated with existing microcontrollers into a broad range of mobile products, home appliances and other systems."

"We continue to see a strong focus on touchscreen technology in handset markets and expect all the major manufacturers to release touchscreen phones in 2009. Also, we expect to see tighter integration of touchscreens with software and hardware in 2009, which will drive greater touchscreen adoption and a faster transition to capacitive technology from resistive technology," said Amy Leong, research director at Gartner Dataquest.

The FMA1127 is available now in a variety of packages that support as many as 12 sensor input channels and 12 DIOs. The 20-, 24- and 30-pin SSOP versions provide DIOs of 2, 3 and 6, and sensor inputs of 6, 9 and 12, respectively.

QFN packages are also available. The 24-pin QFN touch sensor controller provides 3 DIOs and 6 sensor inputs; the 32-pin QFN touch sensor controller offers 8 DIOs and 9 sensor inputs; and the 40-pin QFN provides 12 sensor inputs and 12 DIOs. Pricing begins at $1.40 each in 10,000-unit quantities.

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