Robust sealed touch panels

The sensors offer designers the opportunity to build robust, sealed and secure control panels for applications such as domestic appliances, kiosks, security panels and portable instruments. In addition, the ability to operate at 1.8VDC makes the sensor chips equally suitable for use in mobile phones, MP3 players and other hand-held devices. Key sizes, shapes and placement are almost entirely arbitrary, and each can be individually tuned via an I2C interface for sensitivity, response time and other parameters. This ensures great flexibility in aesthetic design. The devices make use of a new variant of charge-transfer sensing known as ‘transverse charge-transfer’. This matrix format minimizes the number of required scan lines and, unlike older methods, does not require one chip per key, so it greatly simplifies circuit design and cuts costs. External circuitry consists of only a few passive components.



Like all other devices in the QMatrix family, the QT60160 and QT60240 feature adaptive automatic calibration and drift compensation for life, so no adjustment is ever necessary. In another aid to reliable operation, Quantum’s patented adjacent key suppression function ensures that if more than one key is partly covered by the operator’s finger, only the intended key registers a touch.



Traditional capacitive touch switches are susceptible to interference, particularly in the increasingly RF-rich environments now prevalent. QMatrix chips overcome this problem using spread-spectrum modulation to provide high levels of noise immunity and to minimize emissions.



The QT60160 and QT60240 come in an MLF-32 package. Prices start from $0.95 each for the 16-key part and $1.20 each for the 24 key version, based on quantities of 100,000.