A 1.5% jitter PLL clock generation system for a 500-MHz RISC processor

We have developed a clock generation system for RISC processors. The system consists of two parts of a PLL, a frequency multiplier, and a phase aligner. The multiplier can multiply the input clock frequency by 2, 4, and 8, and can accomplish a wide frequency range of output clocks, from 60 MHz to 660 MHz. Jitter is reduced to 1.5% of the output clock period by separating the clock generation system into a frequency multiplier and a phase aligner, and by developing a new differential loop filter with high sensitivity phase detection. The phase aligner reduces clock skew between the processor and peripheral LSIs. The system is fabricated with 0.4-/spl mu/m CMOS triple-layer Al process technology and operated at 3.3 V. >