Patent ID: 8514199
Filing Date: 2013-08-20
Classification: G06F,H03K

Abstract:
1. A capacitance sensing apparatus used for a capacitive touch panel and electrically connected to one electrode of the capacitive touch panel through a connection node to measure a capacitance on the electrode, the capacitance sensing apparatus comprising: a first discharging current source electrically connected the connection node to provide a first discharging current; a second discharging current source electrically connected the connection node to provide a second discharging current, where the first discharging current is larger than the second discharging current; a differential comparator comprising a first input end electrically connected to the connection node and a second input end; a reference voltage source electrically connected to the second input end, wherein the reference voltage source receives a predetermined reference voltage and a DC common voltage of an liquid crystal display to generate a modified reference voltage, wherein the DC common voltage is also electrically connected to the capacitive touch panel; wherein the differential comparator generates a pulse width modulation signal by comparing the modified reference voltage and an input voltage, which is present at the connection node and resulted from a touch on the capacitive touch panel; wherein the pulse width modulation signal indicates the capacitance on the electrode.