An integrated circuit includes a pull-up circuit, an electrostatic discharge (ESD) primary circuit, and a pull-down circuit. The pull-up circuit is coupled between a pad and a first voltage terminal. The ESD primary circuit includes a first terminal which is coupled to the pad and the pull-up circuit, and a second terminal coupled to a second voltage terminal different from the first voltage terminal. The pull-down circuit has a first terminal which is coupled to the pad, the ESD primary circuit and the pull-up circuit, and a second terminal coupled to the second voltage terminal. The pull-down circuit includes at least one first transistor of a first conductivity type having a first terminal coupled to the first terminal of the pull-down circuit. A breakdown voltage of the at least one first transistor is greater than a trigger voltage of the ESD primary circuit.