The Peripheral Touch Controller (PTC) acquires signals to detect a touch on capacitive sensors. The external capacitive touch sensor is typically formed on a PCB or a transparent substrate with a transparent or translucent material such as indium tin oxide (ITO) or PEDOT. An increasingly popular implementation is printing the sensor electrodes directly on the backside of the touch surface using conductive inks. The sensor electrodes are connected to the analog front end of the PTC through the I/O pins in the device. The PTC supports both mutual and self-capacitance sensors.
In Mutual Capacitance mode, sensing is done using capacitive touch matrices in various X-Y configurations. The PTC requires one pin per X-line and one pin per Y-line. See Figure 1.
In Self-Capacitance mode, the PTC requires one pin (Y-line) for each touch sensor. See Figure 2.
The number of available pins and the assignment of X- and Y-lines depend on both package type and device configuration.