Patent ID: 8305360

Claim:
A sensing circuit for a capacitive touch panel, comprising: a sensing signal part for generating a sensing signal according to a capacitance of the capacitive touch panel and a noise which is received by the sensing signal part, wherein the capacitance of the capacitive touch panel at a touched condition is different from the capacitance of the capacitive touch panel at an untouched condition, wherein the sensing signal part comprises: a sensing unit for receiving the noise through a parasitic capacitance, the sensing unit having a first equivalent capacitance or a second equivalent capacitance, wherein the first equivalent capacitance is an equivalent capacitance of the capacitance of the capacitive touch panel at the touched condition and the parasitic capacitance, and the second equivalent capacitance is an equivalent capacitance of the capacitance of the capacitive touch panel at the untouched condition and the parasitic capacitance; and a sensing signal generating unit coupled to the sensing unit, for generating the sensing signal according to the first equivalent capacitance and the noise or according to the second equivalent capacitance and the noise; a reference signal part for receiving the noise and outputting a reference signal, the reference signal part having the same electrical conditions as the sensing signal part, wherein the reference signal part comprises: a reference unit, for receiving the noise, the reference unit having a third capacitance, wherein the third capacitance simulates the capacitance of the capacitive touch panel at the untouched condition and the parasitic capacitance; and a reference signal generating unit coupled to the reference unit, for outputting the reference signal according to the third equivalent capacitance and the noise, wherein the reference unit has the same circuits as the sensing unit, and the reference signal generating unit has the same circuits as the sensing signal generating unit; and an integrator for receiving the sensing signal and the reference signal, subtracting the reference signal from the sensing signal to generate an output signal.