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Product category: Probes and sensors
News Release from: STMicroelectronics | Subject: Touch sensor
Edited by the Manufacturingtalk Editorial Team on 02 July 2007

Touch sensor needs no extra parts on
sensor lines

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STMicroelectronics has introduced its lowest-power-consumption touch sensor, the 'S-Touch', with fast response times and no need for extra components on sensor lines.

STMicroelectronics has announced a family of ultra-low-power touch-sensor chips, following the signing of a technology-licensing agreement with the Korean company ATLab The sensors are intended for portable applications such as mobile phones, PDAs, notebook PCs and media players, as well as for the cost-sensitive white-goods market

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

The first products in the family are 8-channel and 12-channel devices.

This new hardwired touch-sensor family complements ST's recently-announced MCU-based 'QST' series, which enables intelligent touch-sensitive control interfaces for more complex applications and - at the other end of the scale - in simpler products where the sensor's MCU can also control multiple secondary functions.

The combined sensor portfolio positions ST as the only semiconductor supplier to provide a full range of touch-sensor solutions, meeting a wide spread of requirements and conditions across different industries.

ST has implemented the hardwired finite state machine, at the core of the S-Touch family, in optimised silicon, which requires very little power: consumption is around five to ten times lower than conventional touch-sensor solutions, with a sleep-mode consumption of just 1 microamp.

The sensor lines from the device to the application's touch pads do not need the external RC (resistor-capacitor) networks that are typically required in other solutions, and the sensors themselves are tiny - the 8-input device uses a 2.6 x 1.8mm QFN16 package - ensuring a very compact solution that is some 80 percent smaller than existing equivalent solutions, and highly cost-competitive.

The sampling time of the sensor, at 2 milliseconds, is also among the fastest in the industry Future products in this family will integrate proprietary technology from ST's new Xpander Logic family, which helps to overcome limitations in the number of Input/Output (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 a wide range of additional intelligent functions through a fast I2C 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 (Pulse-Width Modulation) controller.

By combining ST and ATLab IP (Intellectual Property) in this way, S-Touch will be able to realise 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.

ST also plans to explore the possibility of extending the collaboration with ATLab, especially in advanced digital IP design services in specific areas.

The technology provides an alternative to ST's MCU-based QST series, the two families ensuring the widest range of touch-sensing design options to meet styling, material and functional requirements.

Samples of the 12-channel STMPE1208 will be available within the first half of 2007, with volume production planned for September.

The 8-channel STMPE821 will be sampling in September 2007 and in volume production in January 2008.

The devices are priced at $1.60 and $1.40, respectively, in quantities of 100,000 pieces.

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