Abstract: A digital approach of on-die adaptive termination resistors control circuit is described in this paper. Current source is used as the reference resistor and digital signals as control signals for termination matching. We proposed a new area efficient lock circuit to make the termination resistorss table after termination matching. The Layout design is based on SMIC 0.18μm 3.3 V／1.8 V CMOS mixed-signal process and was used in a USB 2.0 transceiver successfully.