A 2.5Gb/s oversampling clock and data recovery circuit with frequency calibration technique

In this paper, a 2.5-Gb/s oversampling clock and data recovery (CDR) circuit with frequency calibration is realized for optical communication. The CDR circuit contains a fractional-N phase-locked loop (PLL), a delta-sigma modulator (DSM) and a data recovery circuit. The recovered clock is adjusted by the DSM for phase and frequency tuning, incorporating with the phase detector, when the incoming data rate changes. The CDR circuit is implemented with TSMC 0.18-um 1P6M CMOS technology. The simulation results show the proposed CDR circuit recovers the incoming data.