Patent ID: 8493358

Claim:
A touch-sensitive apparatus, comprising: a panel comprising a touch surface and a plurality of electrodes defining an electrode matrix, the plurality of electrodes comprising a plurality of drive electrodes and a plurality of receive electrodes, each drive electrode being capacitively coupled to each receive electrode at a respective node of the matrix, the panel being configured such that a touch on the touch surface proximate a given one of the nodes changes a coupling capacitance between the drive electrode and the receive electrode associated with the given node; a drive unit configured to generate drive signals and to deliver the drive signals to the drive electrodes; a sense unit including an open-loop transistor-based amplifier and configured to generate, in response to the drive signals, response signals for the plurality of receive electrodes, an amplitude of each of the response signals being responsive to the coupling capacitance at the associated node; a charge accumulator adapted to provide an accumulated signal for each node based on a corresponding response signal generated by the sense unit; and a measurement unit configured to measure the accumulated signals from the charge accumulator and to determine therefrom the positions of multiple temporally overlapping touches, if present, on the touch surface.