Norwood, Mass. Advanced sensing technology in Analog Devices, Inc.'s programmable 14-channel capacitance-to-digital converter (CDC) for handheld consumer applications is said to enable touch controls that are paper-thin yet highly reliable.
Using ADI's advanced capacitance sensor core, the AD7142 CDC has the capability to automatically adjust to rapidly changing climatic conditions, making it especially suitable for mobile applications. Other battery-powered applications include MP3 players, digital cameras, television remote controls, and gaming devices.
"Capacitance sensors, which enable finger-driven screen navigation, are fast replacing mechanical input devices to improve the look and feel of screen controls," said Pat O'Doherty, ADI's product line director, Precision Signal Processing.
The 16-bit, 240-kHz AD7142 converter offers advantages over competing alternatives, including higher immunity to environmental factors such as temperature and humidity that would degrade performance in other capacitance sensors, O'Doherty said.
Full power mode is less than 1.0 milliamp, and shutdown current is less than 2.0 microamps. The CDC's power consumption is 50 percent lower than similar devices, O'Doherty said. The part also offers the capability to flexibly trade-off output rate and power. ADI's AD7142 is available in a choice of SPI or I(2)C compatible interfaces.
Other features include a 30-Hz update rate at maximum sequence length and better than one femto farad resolution. With 14 inputs, the AD7142 can be programmed for a variety of sensor configurations, such as finger-driven scroll bars, eight-way position sensors, and scroll wheels that drive pop-up menus, making it easier to browse through large files of music, pictures and video, O'Doherty said.
The AD7142 CDC is programmable, and includes adaptive threshold and sensitivity algorithms that allow the chip to adjust to the user's finger size, according to O'Doherty.
The CDC allows the end-user to adjust individual sensor sensitivity levels to suit their style and touch. The AD7142 has a unique automatic environmental compensation feature that performs calibration digitally on-chip, ensuring error-free sensor performance at all times, regardless of climate conditions, O'Doherty said. "The device performs this continuous calibration transparently to the user, so there will be no false touches or non-registered touches on the external sensors," he said.
Unlike competitors' module offerings, the AD7142's single chip, IC-based solution provides a library of sensor sizes, allowing manufacturers to customize the shape of capacitance sensors, O'Doherty said. In addition, ADI offers sensor reference designs for a variety of end user applications.
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An evaluation board can be purchased for $199.00. The AD7142 is sampling now, with full production expected in February. The device is offered in a 32-lead 5 x 5 mm LFCSP and operates from a 2.7 V to 3.3 V supply. High-volume pricing is $1.09. Click here for the AD7142 data sheet.
Analog Devices, 1-800-262-5643, www.analog.com.