Introduction
The AT42QT2100 (QT2100) is an easy-to-use sensor IC based on the Atmel-patented charge-transfer (QT™) principles for robust operation and ease of design. This device has many advanced features which provide for reliable, trouble-free operation over the life of the product. In particular the QT2100 features advanced self-calibration, drift compensation, and fast thermal tracking. The QT2100 can tolerate some fluctuations in the power supply, and in many applications will not require a dedicated voltage regulator.

The QT2100 is capable of detecting near-proximity or touch on up to seven electrodes and a slider/wheel. It allows electrodes to project sense fields through any dielectric such as glass or plastic. These electrodes are laid out as a scroller (slider or wheel), plus seven additional independent keys.

Each key channel can be tuned for a unique sensitivity level by simply changing a corresponding external Cs capacitor, whereas the slider/wheel sensitivity can be changed dynamically through SPI commands. Any number of key channels can be optimized for operation as hand proximity sensors by increasing the sensitivity for the corresponding channel.