US Patent 7809345 Digital PLL and applications thereof

A digital phase locked loop (PLL) includes a digital phase detector, a digital loop filter, a digitally controlled oscillation module, and a variable feedback divider. The digital phase detector is coupled to produce a difference signal based on a phase difference between a reference oscillation and a feedback oscillation. The digital loop filter is coupled to process the difference signal to produce a control signal. The digitally controlled oscillation module is coupled to generate an output oscillation based on the control signal. The variable feedback divider is coupled to produce the feedback oscillation from the output oscillation based on a divider value and a controlled variable delay.