Patent ID: 8310381

Claim:
An integrated circuit device that senses actuation of a capacitive touch key, comprising: an analog-to-digital converter (ADC) having a sampling capacitor, wherein the ADC converts an analog voltage on the sampling capacitor to a digital representation thereof; a digital processor coupled to a digital output of the ADC; a switch matrix controlled by the digital processor; a digital driver controlled by the digital processor; a first node adapted for coupling to a capacitive touch key, the first node is coupled to the sampling capacitor through the switch matrix; a second node adapted for coupling to the capacitive touch key, the second node is coupled to the digital driver through the switch matrix; wherein a voltage pulse from the digital driver and through the capacitive touch key charges the sampling capacitor to a first voltage in proportion to a capacitance ratio thereof, wherein when an object having a capacitance to a common potential is in close proximity to the capacitive touch sensor some of the voltage pulse through the capacitive touch sensor is diverted from the sampling capacitor to the common potential, and whereby the sampling capacitor is charged to a second voltage when the object is in close proximity to the capacitive touch key, wherein the second voltage is less than the first voltage.