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Touch controller handles ON/OFF, wake-up trigger

Posted: 26 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:touch sensor? control panel? touch controller?

STM8T141 touch-sensor controller

STMicroelectronics has launched a touch-sensor controller that improves the performance and styling by replacing traditional buttons of main power-on/off control or to trigger wake-up from battery-saving sleep modes.

The success of wireless devices in the home, office and on the road is leading to more and more battery-powered nomadic products that must achieve long battery recharge intervals while also providing powerful functionality such as advanced sensing capabilities that can detect either human touch or proximity. ST's new chip, the STM8T141, helps designers meet both of these demands.

Already in production for a leading cellphone maker, the 8-pin STM8T141 draws a current as low as 11?A from the battery and can detect user presence via the touch-sensor electrode, responding quickly to wake the system from a low-power sleep mode. The chip is designed to monitor a single touch-sensing electrode embedded on the control panel of the end product or in the outer casing. The sensor may be hidden, or its position indicated using a printed, overlaid or illuminated icon.

The new controller also supports proximity sensing, allowing equipment to be controlled without direct contact from the user. This allows the sensor to control power-saving features such as system wake-up on user detection, or features for added convenience such as automatic backlight activation supporting find-in-the-dark capability. Hence using the STM8T141 for touch or proximity detection helps product stylists achieve their desired look and feel in a wide variety of product designs.

The STM8T141 features built-in calibration and compensation, which saves time during product manufacture and allows touch sensing to operate reliably for the lifetime of gadgets such as kitchen appliances, universal remote controls, game terminals, home-A/V products, wireless keyboards, personal media players, audio headsets and many other products. The device also supports a driven electrode-shielding wire, which protects against noise from external sources without the reduction in electrode sensitivity experienced with a grounded shield.

The touch controller features configurable single output for reporting touch or proximity detection with four sensitivity levels allowing adjustment for panel material and thickness. The devices also packs capacitive-charge-transfer sensing technique and an on-chip voltage regulator that enables enhanced performance and low parts count. In addition, the STM8T141 features self and automatic recalibrations, environment compensation filter, sensitivity threshold and de-bounce filter.

A number of development tools are available from ST to enable fast design starts. The STM8T141-EVAL evaluation kit provides an easy-to-use and low-cost demonstration of the chip's touch and proximity features. In addition, the ST-TSLINK programming dongle and STM8T14X-SB socket programming board are used with the STVP PC-based programming tool for fast and efficient product configuration.

The STM8T141 is already sampling to lead customers in the 3mm x 2mm x 0.6mm ultrasmall and low-profile DFN8 package, and is now in volume production. High volumes are available immediately in the narrow variant of the well-known SO-8 package for pricing of $0.45 in quantities of 10,000.

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