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 < 260 fs (f/1667-50 GHz). The VCO's compact area of 0.006 mm² is the smallest among LC VCOs with a comparable tuning range.