A system-on-chip 1.5 GHz phase locked loop realized using 40 nm CMOS technology

Abstract

This work presents the design and realization of a fully-integrated 1.5 GHz sigma-delta fractional-N ring-based PLL for system-on-chip (SoC) applications. Some design optimizations were conducted to improve the performance of each functional block such as phase frequency detector (PFD), voltage-controlled oscillator (VCO), filter and charge pump (CP) and so as for the whole system. In particular, a time delay circuit is designed for overcoming the blind zone in the PFD; an operational amplifier-feedback structure was used to eliminate the current mismatch in the CP, a 3rd LPF is used for suppressing noises and a current overdrive structure is used in VCO design. The design was realized with a commercial 40 nm CMOS process. The core die sized about 0.041 mm2. Measurement results indicated that the circuit functions well for the locked range between 500 MHz to 1.5 GHz.