Touch Sensor Undercuts Mechanical Switches

Sporting a lower price tag than mechanical switches, the QT1100A-ISG 10-key touch-sensor chip is capable of detecting near proximity or touch. Each key operates through a channel that projects an independent sense field over 10-mm thick glass or plastic. The channels can be tuned individually via the chip's serial interface or user-configured to suit the application. Reliability features include automatic calibration, adjacent key suppression (AKS), and burst-mode spread-spectrum modulation. The device recalibrates each channel automatically on power up. AKS compares the signal received from each channel to ensure that only the dominant touch registers as a key touch, eliminating false key presses. Spread-spectrum modulation provides noise rejection to eliminate false triggering while also reducing RF emissions. Other features include SPI and UART interfaces and a scan-port output that simulates a membrane keyboard. Available in a lead-free, 48-pin SSOP, price is under $2 each in volume. QUANTUM RESEARCH GROUP, Pittsburgh, PA. (412) 391-7367.