A 4.25GHz–4.75GHz calibration-free fractional-N ring PLL using hybrid phase/current-mode phase interpolator with 13.2dB phase noise improvement

A calibration-free ring oscillator based fractional-N clock multiplier using hybrid phase/current-mode phase interpolator is presented. Fabricated in 65nm CMOS process, the prototype generates fractional frequencies from 4.25GHz-to-4.75GHz with in-band noise floor of −104dBc/Hz and 1.5ps integrated jitter. The clock multiplier achieves power efficiency of 2.4mW/GHz and FoM of −225.8dB.