Introduction
The AT42QT2120 (QT2120) is a QTouchADC sensor driver. The device can sense from one to 12 keys, dependent on mode. Three of the keys can be used as sense channels for a slider or wheel, leaving a maximum of nine standard touch keys. The device also supports the use of proximity sensors and a guard channel.

The QT2120 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 and no external Cs capacitors are required.

The QT2120 modulates its bursts in a spread-spectrum fashion in order to heavily suppress the effects of external noise, and to suppress RF emissions. The QT2120 uses a QTouchADC method of acquisition. This provides greater noise immunity and eliminates the need for external sampling capacitors, allowing touch sensing using a single pin.

The QT2120 can operate in two ways; comms and standalone.