A 0.004-mm $^{2}$ Portable Multiphase Clock Generator Tile for 1.2-GHz RISC Microprocessor

Portable multiphase clock generators capable of adjusting its clock phase according to input clock frequencies have been developed both in a 0.18-mum and in a 0.13-mum CMOS technologies. They consist of a full-digital CMOS circuit design that leads to a simple, robust, and portable IP. In addition, their open-loop architecture lead to no jitter accumulation and one-cycle lock characteristic that enables clock-on-demand circuit structures. The implemented low power clock generator tile in a 0.13-mum CMOS technology occupies only 0.004 mm 2 and operates at variable input frequencies ranging from 625 MHz to 1.2 GHz within a plusmn 2% phase error having one-cycle lock time.