Patent ID: 7541816

Claim:
A capacitive sensor, comprising: a sensing electrode; a sensing capacitor; a first switch element having a first terminal, a second terminal, a third terminal, a fourth terminal and an input terminal, wherein the input terminal of the first switch element is coupled to the sensing electrode, the first terminal of the first switch element is coupled to a first common voltage, the second terminal of the first switch element is coupled to a first terminal of the sensing capacitor, the third terminal of the first switch element is coupled to a second common voltage, and the fourth terminal of the first switch element is coupled to a second terminal of the sensing capacitor; a second switch element having a first terminal and a second terminal, wherein the first terminal of the second switch element is coupled to the first terminal of the sensing capacitor, and the second terminal of the second switch element is coupled to the first common voltage; and a third switch element having a first terminal and a second terminal, wherein the first terminal of the third switch element is coupled to the second terminal of the sensing capacitor, and the second terminal of the third switch element is coupled to the second common voltage, wherein, a sensing time is divided into a first period, a second period, a third period and a fourth period, in the first period, the first terminal of the first switch element is electrically connected to the input terminal of the first switch element, in the second period, the second terminal of the first switch element is electrically connected to the input terminal of the first switch element, and the first terminal of the third switch element is electrically connected to the second terminal of the third switch element, in the third period, the third terminal of the first switch element is electrically connected to the input terminal of the first switch element, and in the fourth period, the fourth terminal of the first switch element is electrically connected to the input terminal of the first switch element, and the first terminal of the second switch element is electrically connected to the second terminal of the second switch element.