The proposed on-die termination (ODT) calibration method is implemented by using a 0.18um CMOS technology. The proposed ODT can detect the impedance variations of each ODT/OCD independently with the help of the proposed local PVT variation sensor and can decrease the impedance mismatch error lower than 1% by calibration of global on-chip variation with small area overhead. The measured eye diagram area at 2Gbps is widened by 26% when the ODT is on. The random data rate used for testing the eye diagram is 2Gbps. The global impedance mismatch error is within 1% under the supply voltage variation from 1.7V to 1.9V. The ODT and its calibration circuit occupy 0.003mm2 and 0.015mm2, respectively. The power consumption of the calibration circuit is 10mW at 2Gbps.