Capacitive touch controller enables 'smoother' way to wake devices from sleep modes

The new controller allows replacement of traditional buttons with a touch sensor for main power-on/off control or to trigger wake-up from battery-saving sleep modes. Already in production for a cellphone maker, ST's 8pin STM8T141 draws a current as low as 11 microamps from the battery and can detect user presence via the touch-sensor electrode, responding 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. According to ST, 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. The device features built-in calibration and compensation and 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.