Patent ID: 8483986

Claim:
A calibration method of calibrating an impedance value of an output driver which is included in a semiconductor device and which is connected to a first external terminal of the semiconductor device, the semiconductor device including a calibration circuit comprising a replica circuit which is identical in structure with the output driver and which is connected to a second external terminal of the semiconductor device, the method comprising: supplying, to the replica circuit, a voltage condition on which the output driver causes a maximum current to flow; and controlling an impedance value of the replica circuit so that the impedance value of the replica circuit becomes equal to a resistance value of an external resistor which includes a first end connected to the second external terminal and which is placed outside of the semiconductor device and, thereby, the impedance value of the output driver is matched with the impedance value of the replica circuit, wherein the voltage condition is defined by a voltage between a source terminal and a drain terminal of a first transistor which is included in the output driver and which is connected to the first external terminal, and wherein the voltage between the source terminal and the drain terminal of the first transistor is defined by a difference voltage between first and second voltages which correspond to high-level data and low-level data outputted from the output driver, respectively.