The I/O lines used for analog X- and Y-lines must be connected to external capacitive touch sensor electrodes. External components are not required for normal operation, however, to improve EMC susceptibility, a series resistor of up to 100 kΩ can be added to the Y-lines. In Mutual Capacitance mode, a series resistor of up to 10 kΩ can be added to the X-lines to reduce EMC emissions.