US Patent 9594440 Touch sensing system and method for driving the same

A touch sensing system includes a pen including at least one resonant circuit embedded therein, XY electrodes including X electrodes and Y electrodes perpendicular to the X electrodes, an antenna surrounding the XY electrodes, and a first touch driving circuit which supplies a resonant inductive signal to the XY electrodes, decides a location of the pen based on a resonance magnitude of a resonance signal received through the antenna, and decides a pen pressure of the pen based on a resonant frequency of the resonant circuit and an adjacent frequency of the resonant frequency measured while varying a frequency of the resonant inductive signal.