A fast lock phase-locked loop using a continuous-time phase frequency detector

A continuous-time phase frequency detector (PFD) based on the conventional tri-state PFD is proposed for fast lock charge pump phase-locked loops (CPPLLs) in this paper. The locking time of the PLL can be substantially reduced with the proposed continuous-time scheme. During the period that the best tracing and acquisition properties are required, the bandwidth of the PLL can be increased to decrease the locking time with the proposed continuous-time PFD. Afterwards, the bandwidth of the PLL is recovered to the original value to minimize output jitter due to external noise. Any conventional tri-state PFDs can be improved with the proposed continuous-time architecture. The proposed architecture is realized in a standard CMOS 0.35 mu m technology. The simulation results demonstrate that the proposed continuous-time PFD is effective to get more speedy locking time.