A simple precharged CMOS phase frequency detector

摘要

We propose a simple precharged CMOS phase frequency detectorn(PFD). The circuit uses 18 transistors and has a simple topology.nTherefore, the detector, in a 0.8-Μm CMOS process, works up to clocknfrequencies of 800 MHz according to SPICE simulations on extractednlayout. Further, the detector has no dead-zone in the phasencharacteristic which is important in low jitter applications. The phasenand frequency characteristics are presented and comparisons are made tonother PFDs. The phase offset of the detector is sensitive to differencesnof the duty-cycle between the inputs. Mixed-mode simulations arenpresented of the lock-in procedure for a phase-locked loop (PLL) wherenthe detector is used. Measurements on the detector are presented for antest-chip with a delay-locked loop (DLL) where the phase detectionnability of the detector has been verified