A novel wide frequency range 65nm CMOS VCO

In this paper a novel ring oscillator based VCO using a programmable low-dropout regulator (LDO) for coarse frequency tuning, which offers wide tuning range, low phase noise and low die area for integer or fractional-N PLLs is proposed. This design is using two paths to cover more frequencies. The high frequency path uses three delay cells, while the lower frequency path enables two more delay cells to reduce the output frequency. The frequency coverage is 2.75 – 3.7 GHz and 4.5 – 5.7 GHz. Finally, the ring oscillator is designed using 65nm TSMC process with a supply voltage of 1.5V for the LDO and 1 - 1.4V for the ring oscillator. The phase noise is -99.78 dBc/Hz at 1MHz offset, while the power consumption of the full design is 29mW.