A Fast-Locking Digital Phase-Locked Loop

A conventional digital phase-locked loop (DPLL) is designed using [1] to operate at 1GHz using 0.18 \mu m CMOS technology; its lock time is 4.19µs. By adding a coarse/fine tuning control unit composed of a digital-to-analog converter (DAC) and a counter as well as switching the currents of the charge pump, a fast-locking DPLL results, with a lock time of 1.02 us, i.e. an improvement by a factor of 4. Simulations for both DPLLs verified the performance improvement due to using a fast-locking technique.