An all-digital phase-locked loop with 50-cycle lock time suitable for high-performance microprocessors

A frequency-synthesizing, all-digital phase-locked loop (ADPLL) is fully integrated with a 0.5 /spl mu/m CMOS microprocessor. The ADPLL has a 50-cycle phase lock, has a gain mechanism independent of process, voltage, and temperature, and is immune to input jitter. A digitally-controlled oscillator (DCO) forms the core of the ADPLL and operates from 50 to 550 MHz, running at 4/spl times/ the reference clock frequency. The DCO has 16 b of binarily weighted control and achieves LSB resolution under 500 fs.<
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