Patent attributes
A hybrid analog/digital phase-lock loop for low-jitter synchronization provides a mechanism for generating a low-jitter clock from a timing reference that has a high jitter level. A numerically-controlled analog oscillator provides a clock output and has an input for receiving a rational number. The rational number represents a ratio between the frequency of the clock output and the frequency of another stable clock provided to the circuit. A counter divides the frequency of either the clock output or the stable clock, providing feedback or feed-forward control of the analog oscillator, respectively. The circuit also includes a digital phase-frequency detector for detecting an on-going phase-frequency difference between an input timing reference and an output of the divider and a digital loop filter for filtering the output of the phase-frequency detector to provide the rational number that controls the frequency of the numerically-controlled analog oscillator.
