Applications of the TCA6408A-Q1 has this device connected as a target to an I²C controller (processor), and the I²C bus may contain any number of other target devices. The TCA6408A-Q1 is in a remote location from the controller, placed close to the GPIOs to which the controller needs to monitor or control.

A typical application of the TCA6408A-Q1 operates with a lower voltage on the controller side (V_CCI), and a higher voltage on the P-port side (V_CCP). The P-ports can be configured as outputs connected to inputs of devices such as enable, reset, power select, the gate of a switch, and LEDs. The P-ports can also be configured as inputs to receive data from interrupts, alarms, status outputs, or push buttons.