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This paper presents a 5GHz phase-locked loop (PLL) with a fast-locking capability. During frequency locking, the proposed fast-settling technique dynamically adjusts the divide ratio of the frequency divider to keep the instantaneous phase error at the PFD input small. As a result, the locking time is greatly reduced. At a loop bandwidth of 20kHz, the measured settling time is less than 10µs, which is roughly 14× faster than a traditional PLL. Fabricated in a 0.18µm CMOS process, this PLL dissipates 9.5mA from a 1.8V supply. The measured phase noise is −117.5dBc/Hz at 1MHz offset.