35.2 Overview

The Peripheral Touch Controller (PTC) detects touch inputs on capacitive sensors. The external capacitive touch sensor is typically formed on a PCB, and the sensor electrodes are connected to the analog front end of the PTC through the device’s I/O pins. The PTC supports both mutual and self-capacitance sensors, which can be configured as buttons, wheels or sliders.

A self-capacitance sensor consists of a conductor plate with one wire connected directly to an I/O pad. In Self-Capacitance mode, the PTC requires one pin (Y-line) for each touch sensor, as shown in Figure 35-1.

A mutual capacitance sensor consists of two conductor plates, each connected to an I/O pad. The mutual capacitance between the two plates is measured by driving the first plate and sensing the second one. In Mutual Capacitance mode, sensing is performed using capacitive touch matrices that support various X-Y configurations. The PTC requires one pin per X-line and one pin per Y-line, as shown in Figure 35-2.