Infrared touch input device and light emitter activation circuit.

摘要

A touch input device, suitable for use in detecting the presence of an opaque element within a display area bounded by light emitting elements and light detecting elements includes light emitter activating circuitry in which the light emitting elements are individually selectable. Each light emitting element is contained within a matrix (70) and source drivers (60) and sink drivers (80) are effective to select a specific row and column address for each individual light emitter. Current for the light emitters is provided by a voltage source which is chose for compatibility with the logic used in the touch input system. A charge pump (50) operating sequentially with the selection light emitting elements is used to establish a voltage greater than the normal supply voltage to overcome the voltage drops of the source driver (60) and sink driver (80) and the activated light emitter to insure light emission greater than a minimum threshold. <IMAGE>