Introduction
The AT42QT1040 (QT1040) is a digital burst mode charge-transfer (QT™) capacitive sensor driver designed for touch-key applications. The device can sense from one to four keys; one to three keys can be disabled by not installing their respective sense capacitors. Any of the four channels can be disabled in this way.

The device includes all signal processing functions necessary to provide stable sensing under a
wide variety of changing conditions, and the outputs are fully debounced. Only a few external
parts are required for operation.

The QT1040 modulates its bursts in a spread-spectrum fashion in order to heavily suppress the
effects of external noise, and to suppress RF emissions.