STMicroelectronics has introduced a series of capacitive touch sensors

     STMicroelectronics has introduced the QST108, the first product in the company's capacitive touch sensor family, which enables stylish, innovative user interfaces for a wide range of application devices. The QST series is all digital standard products based on proven, patented technology ST recently acquired from Quantum Research Group. ST is the first semiconductor company to be licensed with QProxTM technology.

     Touch-sensitive controllers are fast becoming the preferred alternative to electromechanical switches, as designers use these products to create a sleek, inexpensive, and versatile user interface for a variety of devices where durability, ease of use and price are key considerations. With the QST series, it is easy to achieve closed backlit sensing surfaces, and manufacturers can significantly reduce the cost of touchpads, while also designing a novel and stylish user interface. The QST108, the first product in ST's QST family of capacitive touch sensors, uses a digital-only firmfix-based solution that implements QProx's patented, proven QPROX charge-transfer capacitor technology to provide a single chip intelligent control interface that responds to user touch.

     The QST108 allows customers to design 8-key capacitive touchpads for the user interface of their products using either conventional or flexible printed circuit boards. The induction electrode can be designed within the printed circuit board layout or even printed on the circuit board with conductive ink, and the electrode size and shape of this method are flexible. The QST108 can detect finger touch using electrodes behind a panel made of a non-conductive material (glass or plastic). The external component requirements are very low, and only one sampling capacitor and one resistor per channel are required.

     QST chips require no production line or user calibration. To ensure maximum availability and control consistency, these products integrate sophisticated drift compensation, automatic calibration, noise filtering, and adjacent key suppression algorithms (AKSTM). The configuration of these products allows manufacturers to flexibly design the thickness of the touchpad, and they can design from extremely thin plastic panels to 10mm glass panels. In addition, the various touchpad construction methods pioneered and patented by QST also bring benefits to QST users and are available to ST's customers.

     The QST108 touch sensing controller does not require the development of additional software, allowing different sensing modes to be selected through firmware and selectable resistors. By replacing electromechanical switches with solid-state switches, QST adds flexibility to user interface design, provides a stable and reliable capacitive touch solution, and customers can easily soft-customize QST based on product design, and easily reconfigure QST as different product designs are developed. QST standard solutions significantly reduce development time and costs, allowing design engineers to focus their creativity on system design.

     The new product is initially available in a 32-pin LQFP package. The QST108 drives up to 8 leds. The new product has a built-in PWM(pulse width modulation) controller that can drive a buzzer output or control LED brightness. The shake off touch detection results can be obtained through a single output or I2C interface.

     The QST108 can communicate with the application master controller through the I2C interface. With simple I2C commands, user configurable parameters and control functions such as detection threshold, detection integrator, sensor calibration, low power mode activation, AKS mode and button status and configuration are available.