A low-power multiplying DLL for low-jitter multigigahertz clock generation in highly integrated digital chips

A multiplying delay-locked loop (MDLL) for highspeed on-chip clock generation that overcomes the drawbacks of phase-locked loops (PLLs) such as jitter accumulation, high sensitivity to supply, and substrate noise is described. The MDLL design removes such drawbacks while maintaining the advantages of a PLL for multirate frequency multiplication. This design also uses a supply regulator and filter to further reduce on-chip jitter generation. The MDLL, implemented in 0.18-mum CMOS technology, occupies a total of 0.05 mm(2) of active area and has a speed range of 200 MHz to 2 GHz with selectable multiplication ratios of M -_ 4, 5, 8, 10. The complete synthesizer, including the output clock buffers, dissipates 12 mW from a 1.8-V supply at 2.0 GHz. This MDLL architecture is used as a clock multiplier integrated on a single chip for a 72 x 72 STS-1 grooming switch and has a jitter of 1.73 ps (rms) and 13.1 ps (pk-pk).