Patent ID: 6281687
Filing Date: 2001-08-28
Classification: H03K

Abstract:
A calibration apparatus, comprising:a single calibration resistor having a first terminal and a second terminal;a first calibration circuit of a first transistor type coupled to said first terminal for calibrating a drive impedance of an output driver; and,a second calibration circuit of a second transistor type coupled to said second terminal for calibrating the drive impedance of the output driver,wherein said calibration resistor compensates both said first calibration circuit and said second calibration circuit for use in calibrating the drive impedance, said first calibration circuit and said second calibration circuit do not calibrate the drive impedance at the same time, said first calibration circuit provides a connection from said first terminal to a first supply voltage when said second calibration circuit is calibrating the drive impedance, and said second calibration circuit provides a connection from said second terminal to a second supply voltage when said first calibration circuit is calibrating the drive impedance.