A SIMPLE PRECHARGED CMOS PHASE FREQUENCY DETECTOR

We propose a simple precharged CMOS phase frequency detector (PFD). Th e circuit uses 18 transistors and has a simple topology, Therefore, th e detector, in a 0.8-mu m CMOS process, works up to clock frequencies of 800 MHz according to SPICE simulations on extracted layout, Further , the detector has no dead-zone in the phase characteristic which is i mportant in low jitter applications, The phase and frequency character istics are presented and comparisons are made to other PFD's, The phas e offset of the detector is sensitive to differences of the duty-cycle between the inputs. Mixed-mode simulations are presented of the lock- in procedure for a phase-locked loop (PLL) where the detector is used, Measurements on the detector are presented for a test-chip with a del ay-locked loop (DLL) where the phase detection ability of the detector has been verified.