The AT42QT1040-MMH is a digital burst mode, charge-transfer (QT?) Capacitive Sensor Driver, designed for touch-key applications. It can sense from one to four keys-one to three keys can be disabled by not installing their respective sense capacitors. The device includes all signal processing functions necessary to provide stable sensing under a wide variety of changing conditions. The outputs are fully debounced. Only a few external parts are required for operation. The device modulates its bursts in a spread-spectrum fashion in order to heavily suppress the effects of external noise and to suppress RF emissions.