An on-chip termination (OCT) calibration circuit includes one or more transistors coupled between a first terminal and a supply voltage, one or more transistors coupled between the first terminal and a low voltage, and a feedback loop circuit. The feedback loop circuit compares a signal from the first terminal to first and second reference signals to generate a first calibration code that controls conductive states of the one or more transistors coupled between the first terminal and the supply voltage and a second calibration code that controls conductive states of the one or more transistors coupled between the first terminal and the low voltage. The OCT calibration circuit controls an on-chip termination impedance at a pin using the first calibration code and the second calibration code.