A CMOS clock and data recovery with two-XOR phase-frequency detector circuit

This paper describes a 1.0 Gbps Clock and Data Recovery circuit with a simple PFD structure. The proposed circuit is based on a single loop controlled by a Phase Frequency Detector (PFD) which has two-XOR gates. The VCO composed of four differential buffer stages generates eight differential clocks each spaced by 45/spl deg/. The PFD generates the VCO control signal by comparing two different phase clocks and input data. The circuit operates on 800 Mbps to 1.2 Gbps data rate under 2.5 V supply using 0.25 /spl mu/m-CMOS HSPICE simulation. The circuit is under fabrication. The measured results are presented.