US Patent 7190173 Impedance calibration circuit and method thereof

The present invention discloses an impedance calibration circuit and method for calibrating an equivalent impedance of a semiconductor circuit element. The disclosed impedance calibration circuit includes a reference circuit, a second circuit element, and a controlling circuit. The reference circuit receives a test signal and outputs a first signal. The second circuit element is coupled to the semiconductor circuit element to form a test circuit and receives the test signal and outputs a second signal. The controlling circuit is coupled to the reference circuit and the test circuit for comparing the first signal with the second signal and adjusting the equivalent impedance of the semiconductor circuit element accordingly.