Phase-locked loop with dual phase frequency detectors for high-frequency operation and fast acquisition

The sequential phase frequency detector (PFD) has an unlimited error detection range and the precharge PFD has one and a half times better resolution performance than the sequential PFD. Therefore, by selective operation of the appropriate PFD connected to the well-adjusted charge pump, an unlimited error detection range, a high-frequency operation, and a higher speed lock-up time can be achieved. In this paper, we propose a phase-locked loop (PLL) with dual PFDs in which advantages of both PFDs can be combined. This structure can improve the tradeoff between acquisition behavior and locked behavior.