Patent ID: 7595656

Claim:
An interface circuit for performing signal transmission with a transmission line, comprising: a driver circuit made up of a combination of first transistor controlled based on an input signal and a second transistor; a control circuit that performs selection of on and off of the second transistor; and a terminating resistor that is connected between an output side of the driver circuit and the transmission line, wherein second transistor is turned on or off based on an output of the control circuit, the driver circuit, the control circuit, and the terminating resistor are formed on one identical semiconductor integrated circuit, the control circuit is adapted to detect process variation and temperature variation of a third transistor and a resistor formed on the control circuit, and the control circuit includes a constant current circuit that supplies constant current to the third transistor and the resistor formed on the control circuit, and a detection circuit that detects the process variation and the temperature variation by detecting voltages generated in the third transistor and the resistor respectively by the constant current.