Delay Modulation in Separately Driven Delay Cells Utilized for the Generation of High-Performance Multiphase Signals Using ROs

Abstract

This brief presents a general technique for achieving the highest possible RO oscillation frequency accompanied by lower phase noise in an enhanced circuit design utilizing novel delay cells. The circuit architecture has the delay cells' inputs separated by an optimized skew offset. Skew-offset optimization is attained by integrating a pre-charge/discharge auxiliary feed-forward loop into the separately driven delay cells. This technique reduces the transition time when Supply and GND are simultaneously connected/disconnected to the delay cell's output node. When these delay cells are connected in loops to form a Ring Oscillator, they provide high performance, even/odd multi-phase signals. The proposed methodology is validated in commercial 65nm and 180nm CMOS technologies. The post-layout simulations show that the proposed designs improve the performance by modulating the delay cell output node's charging and discharging. The operating frequency of the proposed design, e.g., for odd stage 5/7 and even stage 4/8/16 stage, is almost 50%/40%, (80%/30%/20%) higher than that of the MSSRO (Multi-Loop Skew based Single-ended Ring Oscillator) with the same number of stages. Additionally, the designs proposed for the targeted phase noise and center frequency consume around 8-20% (odd stages)/ (6-28%) (Even stages) lesser power, a lower supply sensitivity up to 9%, and lower PVT variability up to 6% compared to its equivalent stages MSSRO (3-stages single-ended RO) counterparts in 180 nm CMOS Technology.