Patent ID: 8384689
Filing Date: 2013-02-26
Classification: G06F

Abstract:
1. A switched-capacitor tracking apparatus of a touch panel configured to track a capacitance variation of a panel capacitor, comprising: a variable capacitor; an auxiliary capacitor; a first switch having a first terminal coupled to a first reference voltage and a second terminal coupled to the panel capacitor; a second switch having a first terminal coupled to the panel capacitor; a third switch having a first terminal coupled to a second reference voltage and a second terminal coupled to the variable capacitor; a fourth switch having a first terminal coupled to the variable capacitor and a second terminal coupled to the second terminal of the second switch, wherein the first switch and the third switch are turned on and the second switch and the fourth switch are turned off in a charge period of a first clock signal, and the first switch and the third switch are turned off and the second switch and the fourth switch are turned on in a detection period of the first clock signal; a fifth switch having a first terminal coupled to the second reference voltage and a second terminal coupled to the auxiliary capacitor; a sixth switch having a first terminal coupled to the auxiliary capacitor and a second terminal coupled to the second terminal of the second switch; and a control circuit coupled to the second terminal of the second switch, the control circuit configured to set a capacitance of the variable capacitor according to a first capacitor step value, to compare a third reference voltage and a voltage at the second terminal of the second switch, to control the fifth switch and the sixth switch according to a comparison result, and to accumulate a plurality of the comparison results in a statistics period, wherein if all the comparison results in the statistics period are a first logic value, then the control circuit increases the first capacitor step value, and if all the comparison results in the statistics period are a second logic value, then the control circuit decreases the first capacitor step value.