An Antiharmonic, Programmable, DLL-Based Frequency Multiplier for Dynamic Frequency Scaling

This paper describes a new delay-locked loop (DLL)-based frequency multiplier, which includes a lock controller and a phase detector to solve the false lock problem and overcome the limited locking range of conventional DLLs. By using the multiple clock phases of the DLL, the lock controller is able to indicate whether the delay time of the VCDL is within the correct locking range or not. A differentially controlled edge combiner is also proposed for the frequency multiplication. The antiharmonic DLL-based frequency multiplier, implemented in a 0.18-μ.m CMOS process, occupies an active area of 0.043 mm², and dissipates 36.7 mW at 1.7 GHz. The measured root mean square jitter and peak-to-peak jitter for the multiplied output clock at 1.7 GHz are 2.64 and 16.8 ps, respectively.