Reference Spur Reduction in Sampled-loop filter PLLs by Oversampling

A technique to completely eliminate reference spurs in both Integer-N and Fractional-N charge pump phase locked loops (PLLs) based on an oversampled loop filter architecture is proposed. A rigorous analysis of the performance of the proposed technique in the presence of implementation non-idealities is also presented. It is shown through analysis and simulations that the proposed technique, in addition to completely eliminating reference spurs, adds an insignificant area and power overhead when applied to Integer-N PLLs and less than 6% increase in area and power in case of Fractional-N PLLs.