A 2-4 GHz fast-locking frequency multiplying delay-locked loop

Abstract

A fast-locking fractional-ratio multiplying DLL (FMDLL) for de-skewed on-chip clock frequency multiplication is presented. A new phase detecting controller (PDC) and a dual-path charge pump (CP) have been adopted to achieve shorter locking time and eliminate lock-in fail problems. The proposed fast-locking FMDLL was implemented in a 65-nm CMOS process and occupies an active area of 0.015 mm². It operates over a frequency range of 2.0–4.0 GHz with a programmable frequency multiplication factor of N/M, where N = 4, 5, 8, 10 and M = 1, 2, 3. It achieves a peak-to-peak output clock jitter of 13.5 ps at 4 GHz while consuming 6.7mW at 2 GHz from a 1.2V supply. Compared with the conventional architecture, the locking time has been reduced about 80%.