Analog Devices' New Capacitance-To-Digital Converter Uses Advanced Sensing Technology To Improve Accuracy And Reliability Of Touch Controls In Handheld Consumer Electronics

ADI expands award-winning capacitance sensor portfolio with input device that enables error-free performance in low power mobile environments.

Analog Devices, Inc. introduced a programmable 14-channel capacitance-to-digital converter (CDC) for handheld consumer electronics that enables the design of contemporary touch controls that are paper-thin, yet highly reliable, to improve the user experience. Leveraging the company’s advanced capacitance sensor core, the low power device has the capability to automatically adjust to rapidly changing climatic conditions, making it ideal for mobile environments. Capacitance sensors, which enable finger-driven screen navigation, are fast replacing mechanical input devices to improve the look and feel of screen controls in cellular handsets, MP3 players and digital cameras.

Expanding ADI’s award winning CDC portfolio into consumer applications, the AD7142 offers significant advantages over competing solutions, including higher immunity to environmental factors such as temperature and humidity that would degrade performance in other capacitance sensors. The device’s power consumption is 50 percent lower than competing solutions, making it ideal for battery-powered applications. With 14 inputs, the AD7142 can be programmed for a variety of sensor configurations, such as finger-driven scroll bars, 8-way position sensors, and scroll wheels that drive pop-up menus, making it easier to browse through large files of music, pictures and video.

More about the AD7142 Capacitance-to-digital Converter
Leveraging ADI’s capacitance sensor technology, the AD7142 is highly programmable, and includes adaptive threshold and sensitivity algorithms that allow the chip to adjust to the user’s finger size, making the sensors robust for consumers with large and small fingers. The 16-bit, low noise, high accuracy 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. 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.

In addition, the device’s low power consumption makes it ideal for battery-powered applications, including digital cameras, television remote controls, and gaming devices. Full power mode is less than 1.0 mA, and shutdown current is less than 2.0 μA. The part also offers the capability to flexibly trade-off output rate and power. Available in a choice of SPI or I2C compatible interfaces, the AD7142 works well with ADI’s Blackfin® processors used in handsets and personal media players.

About ADI’s Capacitive Sensor Technology
The AD7142 is enabled by the same capacitance sensor technology that is used in the AD7745, ADI’s CDC targeted for industrial applications – which was the sole winner of a sensor component award at 2005 Best of Sensors Expo Awards. Both devices are built around ADI’s sigma-delta capacitance-to-digital converter processing core.

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 to differentiate their products. In addition, ADI offers sensor reference designs for a variety of end user applications. These reference designs can operate with optional host software, which enables high precision sensing capability.

Availability and Pricing
The AD7142 is now available for sampling, with full production quantities expected in February 2006. The device is offered in a 32-lead 5 mm x 5 mm LFCSP (lead frame chip scale) package and operates from a 2.7 V to 3.3 V supply. The product is available in high volume production for $1.09. The AD7142 Evaluation Board is available now for $199 through the ADI Sales office.