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ST touch sensors use ATLabs capacitive technology

Posted: 09 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:touch-sensor chips? on-chip MCU? embedded systems? user-interface controller?

STMicroelectronics unveils a new family of ultralow-power touch-sensor chips, following the signing of a technology-licensing agreement with the Korea's ATLab Inc. The new hardwired touch-sensor family composed of 8- and 12-channel devices is intended for portable applications and cost-sensitive white-goods.

The S-Touch family uses ATLab's capacitive touch-sensing technology, which is based on a fully-digital architecture that requires no on-chip MCU, memory or firmware to implement control interfaces responsive to their users' touch.

ATLab's patented impedance change-detection engine (ICDE) is capable of detecting changes in capacitance as small as 60fF. Moreover, its unique automatic calibration technology allows S-Touch to be highly tolerant to assembly and PCB variations, EMC interference and water film effects.

New architecture
ST has implemented the hardwired finite state machine, at the core of the S-Touch family, in optimized silicon, which requires very little powerconsumption is around five to ten times lower than conventional touch-sensor solutions, with a sleep-mode consumption of just 1?A. The sensor lines from the device to the application's touch pads do not need the external resistor-capacitor networks that are typically required in other solutions.

The sensors are tinythe 8-input device uses a 2.6-by-1.8mm QFN16 packageensuring a very compact solution that is about 80 percent smaller than existing equivalent solutions and highly cost-competitive. The sampling time of the sensor, at 2ms, is also claimed to be among the fastest in the industry today.

Future products in the family will integrate proprietary technology from ST's new Xpander Logic family, which helps to overcome limitations in the number of I/O ports in MCU-based embedded systems by reassigning I/O-intensive tasks to an ultra-low-power Xpander Logic IC. The technology allows an existing system processor to use additional intelligent functions through an I?C interface, including a keypad controller capable of supporting up to 96 keys, with ghost key, multiple key and hot-key handling and LED brightness control through a PWM controller.

By combining ST and ATLab IP in this way, S-Touch is eyed to become a true one-chip solution for a full user-interface controller, handling a full-size keypad with LED-backlighting control and with capacitive touch-key and resistive touch-screen features. Meanwhile, ST has announced plans to explore the possibility of extending the collaboration with ATLab, especially in advanced digital IP design services in specific areas.

Samples of the 12-channel STMPE1208 will be available in 1H '07, with volume production planned for September. The 8-channel STMPE821 will be sampling in September and will be in volume production in January. The devices are priced at $1.60 and $1.40, respectively, in quantities of 100,000 pieces.

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