US Patent 7551039 Phase adjustment in phase-locked loops using multiple oscillator signals

Phase-locked loop (PLL) logic comprises an oscillator that produces a first oscillator signal and phase detect logic that determines a phase difference between the first oscillator signal and a second oscillator signal. After the second oscillator signal is replaced by a third oscillator signal, the phase detect logic determines another phase difference between the first oscillator signal and the third oscillator signal. The PLL removes the phase difference from the another phase difference to produce an intermediate signal. The oscillator adjusts the first oscillator signal using the intermediate signal.