35.5.1.3.2 Mutual Capacitance Sensor Arrangement

For multiple touch points, self-capacitance scanning alone is insufficient for accurately determining their exact positions. To precisely detect multiple touch points, mutual-capacitance sensing is required.

A mutual capacitance sensor is formed between two I/O lines (X- and Y- electrodes) running either horizontally or vertically, with the intersection working as capacitors plates. The horizontal and vertical lines do not physically connect, forming a mutual capacitance sensor between the X- and Y-electrodes measured by the PTC.

A good way to reduce the number of I/O lines needed to connect a large number of sensors is to use a mutual capacitance sensor array.