A 13.5 to 23 GHz Compact PLL Based on a 0.006mm² Transformer-Based Dual-Resonator Tuned LC VCO in 5nm CMOS

A transformer-based, dual-resonator tuning technique is introduced to enable a wide frequency tuning range LC VCO while occupying a compact area. The VCO, implemented in 5 nm CMOS, overcomes the inductor area constraints imposed by tight bump pitches in scaled CMOS. The VCO is integrated into an integer-N PLL with a measured tuning range of 52% (13.5 to 23 GHz) and an RMS jitter of $\lt 260 \mathrm{fs}$ ($\mathrm{f}_{0} / 1667-50 \mathrm{GHz}$). The VCO’s compact area of $0.006 \mathrm{~mm}^{2}$ is the smallest among LC VCOs with a comparable tuning range.