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This paper presents a 5.4-Gb/s clock and data recovery circuit using a seamless loop transition scheme which has minimal phase noise degradation. The proposed scheme enables the CDR circuit to change the operation mode without output phase noise degradation or stability problems. A modified half-rate linear phase detector reduces the phase error between the data and clock. A tested chip is manufactured using 0.13-μm CMOS technology. The rms jitter of the proposed CDR circuit is 5.98 ps-rms, which is 2.61 ps lower than the CDR circuit with the conventional scheme. The measured power dissipation is 138 mW with output drivers and an embedded 2:1 MUX at 5.4-Gb/s data rate.