Introduction
The AT42QT1085 (QT1085) is an easy to use QTouchADC mode sensor IC based on Atmel principles for robust operation and ease of design. It is intended for any touch-key application. There are four dedicated channels configured as keys (Key 0 – Key 3). Another four channels can be configured as keys or GPIO channels (Key 4 – Key 7 or GPIO 12 – GPIO 15). There are 12 dedicated GPIO channels (GPIO_0 – GPIO_11).

The QT1085 is capable of detecting proximity or touch on the channels configured as keys. The keys can be constructed in different shapes and sizes. Refer to the Touch Sensors Design Guide and Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide, for more information on construction and design methods (both downloadable from the Atmel® website).

Each GPIO channel may be configured as a digital input or output. In output mode, a GPIO pin may be set to output a PWM signal at any of 16 duty cycles (4-bit PWM). The QT1085 allows electrodes to project sense fields through any dielectric such as glass or plastic.

This device has many advanced features which provide for reliable, trouble-free operation over the life of the product. In particular the QT1085 features advanced self-calibration, drift compensation, and fast thermal tracking. The QT1085 can tolerate some fluctuations in the power supply, and in many applications will not require a dedicated voltage regulator.