A Dynamic Phase Error Compensation Technique for Fast-Locking Phase-Locked Loops

This paper presents a fast-locking technique for phase-locked loops (PLLs). In the proposed technique, the polarity and magnitude of the phase error at the phase-frequency detector (PFD) input is continuously monitored during the locking process. The detected phase error is then coarsely compensated by dynamically changing the divide ratio of the frequency divider. The proposed method allows the PLL to maintain a small phase error throughout the frequency acquisition process, thereby reducing the settling time. To further enhance the locking speed, an auxiliary charge pump is employed to supply currents to the loop filter during the fast-locking mode to facilitate a rapid frequency acquisition. The proposed technique is incorporated in the design of a 5-GHz PLL. Fabricated in the TSMC 0.18-μm CMOS technology, the whole PLL dissipates 11 mA from a 1.8-V supply. The measured settling time is considerably improved over previous bandwidth-switching method. At 5.34 GHz, the phase noise measured at 1-MHz offset is -114.3 dBc/Hz, and the reference spurs at 10-MHz offset are lower than -70 dBc.