A touch-sensor controller from STMicroelectronics can replace buttons in mobile phones, portable consumer products and appliances. It allows a touch sensor to be used for main power-on/off control or to trigger wake-up from battery-saving sleep modes. The STM8T141 draws a current as low as 11µA from the battery and 30µA in run mode. It can detect user presence via the touch-sensor electrode, responding quickly to wake the system from a low-power sleep mode. The chip monitors 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 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. The IC has built-in calibration and compensation. It also allows touch sensing to operate reliably for the lifetime of end-products. A driven electrode-shielding wire protects against noise from external sources without the reduction in electrode sensitivity experienced with a grounded shield. The IC has a configurable output for reporting touch or proximity detection and four sensitivity levels to adjust for panel material and thickness.
