Limitations of the Phase-to-Frequency-Detector in Fractional Frequency Synthesizers

In this paper a closed form expression for the phase-to-frequency-detector (PFD) output error, in Fractional Frequency Synthesizers, is obtained. It is demonstrated that the limit frequency of operation for the PFD not only depends on the reset delay signal but also in the setup time of the PFD. With this equations a suitable delay in the reset signal can be selected.