High Sensitive Readout Circuit for Capacitance Touch Panel With Large Size

A readout circuit for large sized capacitive touch screens is presented in this letter. Being different from the conventional readout circuit, the phase conversion module is inserted between the differential sensing structure and the integrating amplifier, to take advantage of both the positive and negative edge of the touch sensing signal for the following integrator. Thus, the sensing output value can be increased as the touch signals are integrated by twice for every clock cycle. Both simulation and measurement results verify that, thanks to the insertion of the proposed phase conversion module, the amplitude of touch sensing circuit's output is increased from 1.4 to 2.8 V. In addition, compared with the frequency increasing method, the proposed scheme features an increase of 40% in the sensing output voltage.