ST releases details of touch-sensor controller

ST Microelectronics has released details of a touch-sensor controller that is said to improve the performance and styling of products such as mobile phones, portable consumer products and appliances.

The new controller replaces traditional buttons with a touch sensor for main power-on/-off control or to trigger wake-up from battery-saving sleep modes.

The use of wireless devices in the home, in the 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, is claimed to help designers meet both of these demands.

Already in production for a mobile-phone maker, the eight-pin STM8T141 draws a current as low as 11mA 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 such as automatic backlight activation supporting a find-in-the-dark capability.

As a result, using the STM8T141 for touch or proximity detection helps product stylists achieve their desired look and feel in a 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 and audio headsets.

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.

Features of the STM8T141 include: a configurable single output for reporting touch or proximity detection; four sensitivity levels allowing adjustment for panel material and thickness; a low consumption of 11mA in low-power mode or 30mA in run mode; a capacitive-charge-transfer sensing technique; an on-chip voltage regulator enabling enhanced performance and a low part count; self calibration; automatic recalibration; an environment compensation filter; a sensitivity threshold; and a de-bounce filter.

Various development tools are available from ST to enable fast design starts.

The STM8T141-Eval evaluation kit provides a low-cost demonstration of the chip's touch and proximity features.

In addition, the ST-TSLink programming dongle and the STM8T14X-SB socket programming board are used with the STVP PC-based programming tool for product configuration.

The STM8T141 is already sampling to lead customers in the 3 x 2 x 0.6mm ultra-small and low-profile DFN8 package and is now in volume production.

High volumes are available now in the narrow variant of the SO-8 package for pricing of USD0.45 (GBP0.29) in quantities of 10,000.

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