Interface circuit and method for controlling switching circuit within interface circuit

An interface circuit, comprising:

• a switching circuit, configured to receive an input signal from an input terminal, and selectively transmit the input signal to an internal circuit;
• an over-voltage detection circuit, configured to detect whether a voltage level of the input signal is greater than a threshold value, and accordingly generate at least one over-voltage signal;
• and
• a control signal generating circuit, configured to generate a control signal according to said at least one over-voltage signal, to control the switching circuit to be in one of three or more states;
• wherein the switching circuit comprises a transistor, and the three or more states comprise a first state, a second state and a third state;
• the first state indicates that a first gate voltage is applied to the transistor and the transistor is therefore conductive, the second state indicates that a second gate voltage that is different from the first gate voltage is applied to the transistor and the transistor is therefore conductive, and the third state indicates that a third gate voltage is applied to the transistor and the transistor is therefore non-conductive.