Design of an Improved CMOS Phase/Frequency Detector

A complementary metal oxide semiconductor (CMOS) phase/frequency detector (PFD) is presented. An improved CMOS D-type master-slave flip-flop is described and adopted in the PFD. Higher speed and lower power operation is attributed to the reduced node capacitance. Charge-sharing phenomena are circumvented in the proposed flip-flop and PFD. The maximum frequency of operation of the PFD is analytically studied. Device-sizing equations, based upon a first-order approximation, for the PFD are derived. The proposed PFD shows improvements in both phase and frequency sensitivities at high operating frequencies. HSPICE simulations of a phase-locked loop (PLL) employing the improved PFD demonstrate a faster frequency acquisition. The PLL simulations also verify that the maximum operating frequency of the PFD is in agreement with our analytical results.