Touchpad with active plane for pen detection

A method for sensing touch in a touch sensor having a plurality of traces and a conducting element, comprising the steps of:

• driving one of said traces with a first waveform;
• driving said conducting element with a second waveform;
• sensing a third waveform on one of said traces to detect a variation in said first waveform due to a touch of a stylus varying a distance between at least one of said traces and said conducting element;
• alternately driving said conducting element with a signal which varies one of the amplitude and phase of said second waveform for capacitively detecting a finger.

A method for sensing touch in a touch sensor having a plurality of traces and a conducting plane, comprising the steps of:

• driving one of said traces with a first alternating triangular waveform of a first frequency;
• driving said conducting plane with a second alternating pulse waveform of said first frequency;
• sensing a third waveform on one of said traces to detect a variation in said first waveform due to a touch of a stylus compressing a distance between at least one of said traces and said conducting plane;
• alternately driving said conducting plane with a DC voltage for capacitively detecting a finger;
• and
• varying one of the phase and amplitude of said second waveform so that said third waveform is within a common amplitude range for detecting said stylus and said finger.

A touch sensor comprising:

• a plurality of traces;
• a conducting element;
• a compressible insulator between said traces and said conducting element;
• a first driver alternately coupled to said traces for driving one of said traces with a first periodic waveform of a first frequency;
• a second driver connected to said conducting plane for driving said conducting element with a second periodic waveform of said first frequency;
• and
• a sensing circuit alternately coupled to said traces for sensing a third waveform on one of said traces to detect a variation in said first waveform due to a touch varying a distance between at least one of said traces and said conducting element.