A simple precharged CMOS phase frequency detector

Abstract

We propose a simple precharged CMOS phase frequency detector (PFD). The circuit uses 18 transistors and has a simple topology. Therefore, the detector, in a 0.8-/spl 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 important in low jitter applications. The phase and frequency characteristics are presented and comparisons are made to other PFDs. The phase 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 delay-locked loop (DLL) where the phase detection ability of the detector has been verified.