Coordinate input device used for inputting characters and drawings into a personal computer/word processor

摘要

A coordinate input device includes (1) a pen switch sensing circuit for providing a power supply to a pen switch in a position sensing pen, and for sensing that the pen switch is turned on and off and (2) a pen switch control circuit for controlling a timing of the power supply. The power supply is provided to the pen switch only when coordinate sensing operations are not affected. The power supply is stopped in order to avoid a voltage change happening to the pen switch when the coordinate sensing operation is affected. Therefore, the pen switch is neither turned on nor turned off during a coordinate sensing period. Consequently, it is possible to avoid a wrong sensing of a coordinate indicated with the position sensing pen.