These digital charge-transfer (“QT”) QMatrixTM ICs are designed to detect human touch on up to 16 or 24 keys when used with a scanned, passive X-Y matrix. They will project touch keys through almost any dielectric, e.g. glass, plastic, stone, ceramic, and even wood, up to thicknesses of 5 cm or more. The touch areas are defined as simple 2-part interdigitated electrodes of conductive material, like copper or screened silver or carbon deposited on the rear of a control panel. Key sizes, shapes and placement are almost entirely arbitrary; sizes and shapes of keys can be mixed within a single panel of keys and can vary by a factor of 20:1 in surface area. The sensitivity of each key can be set individually via simple functions over the serial port by a host microcontroller. Key setups are stored in an onboard eeprom and do not need to be reloaded with each powerup.
These devices are designed specifically for appliances, electronic kiosks, security panels, portable instruments, machine tools, or similar products that are subject to environmental influences or even vandalism. They permit the construction of 100% sealed, watertight control panels that are immune to humidity, temperature, dirt accumulation, or the physical deterioration of the panel surface from abrasion, chemicals, or abuse. To this end they contain Quantum-pioneered adaptive auto self-calibration, drift compensation, and digital filtering algorithms that make the sensing function robust and survivable.
These devices feature continuous FMEA self-test and reporting diagnostics, to allow their use in critical consumer appliance applications, for example ovens and cooktops.
Common PCB materials or flex circuits can be used as the circuit substrate; the overlying panel can be made of any non-conducting material. External circuitry consists of only a few passive parts. Control and data transfer is via an SPI port.
These devices makes use of an important new variant of charge-transfer sensing, transverse charge-transfer, in a matrix format that minimizes the number of required scan lines. Unlike older methods, it does not require one IC per key.
- Second generation charge-transfer QMatrix technology
- Keys individually adjustable for sensitivity, response time, and many other critical parameters
- Panel thicknesses to 50mm through any dielectric
- 16 and 24 touch key versions
- 100% autocal for life - no adjustments required
- SPI slave interface
- Adjacent key suppression feature
- Synchronous noise suppression feature
- Spread-spectrum modulation - high noise immunity
- Mix and match key sizes & shapes in one panel
- Low overhead communications protocol
- FMEA compliant design features
- Negligible external component count
- Extremely low cost per key
- +3 to +5V single supply operation
- 32-pin lead-free TQFP package