Patent ID: 7564258

Claim:
An integrated circuit comprising: a plurality of driver circuits to transmit data; and a calibration circuit coupled to the plurality of driver circuits, the calibration circuit to calibrate a drive current and termination resistance of the plurality of driver circuits, the calibration circuit including: a pad that couples to an external resistor; a first adjustable impedance coupled to the pad, to develop a first voltage at a first node by drawing a first current through the external resistor, wherein the first impedance is controlled by a first control value, and wherein the first control value is based on a comparison between the first voltage and a reference voltage; a second adjustable impedance that is controlled based on the first control value; and a third adjustable impedance, coupled to the second adjustable impedance, to develop a second voltage at a second node by drawing a second current through the second adjustable impedance; wherein the third adjustable impedance is controlled based on a second control value, wherein the second control value is based on a comparison between the first voltage at the first node and the second voltage at the second node.