A high-speed frequency acquisition PLL using phase frequency detector with variable gain

Conventional phase-locked loops (PLL) with a tri-state phase frequency detector (PFD) and a charge pump (CP) typically suffer long locking time in video applications due to low reference frequency (30K Hz~150kHz). In this paper, we propose a novel multi-state phase frequency detector with variable gain which can efficiently reduce the locking time. The post-layout simulation results indicate that the locking time of the PLL using the proposed novel multi-state PFD can be reduced about 49% compared with conventional PFDs.