In this paper, a clock and data recovery (CDR) circuit for a serial link with a half rate 4x oversampling phase and frequency detector structure without a reference clock is described.The PD and FD are designed by 4X oversampling method. The PD, which uses bang-bang method, finds the phase error by generating four up/down signal and the FD, which uses the rotational method, finds the frequency error by generating up/down signal made by the PD output. And the six signals of the PD and the FD control an amount of current that flows through the charge pump. The VCO composed of four differential buffer stages generates eight differential clocks. Proposed circuit is designed using the TSMC 0.18um CMOS technology and operating voltage is 1.8V.

In this paper, a clock and data recovery (CDR) circuit for a serial link with a half rate 4x oversampling phase detector (PD) structure is described. The PD is designed by 4X oversampling method. The PD finds the data_ lead and data _lag by the logical computation to the input data and controls amount of current that flows through the charge pump. The VCO composed of four differential buffer stages generates eight differential clocks. Proposed circuit is designed using the TSMC 0.25um CMOS technology and operating voltage is 2.5V. The circuit is operating between 480Mb/s -1.5Gb/s.