A 5-GHz CMOS Type-II PLL With Low $K_{\rm VCO}$ and Extended Fine-Tuning Range

A 5-GHz dual-path integer-N Type-II phase-locked loop (PLL) uses an LC voltage-controlled oscillator and softly switched varactors in an overlapped digitally controlled integral path to allow a large fine-tuning range of approximately 160 MHz while realizing a low susceptibility to noise and spurs by using a low K _VCO of 3.2 MHz/V. The reference spur level is less than -70 dBc with a 1-MHz reference frequency and a total loop-filter capacitance of 26 pF. The measured phase noise is -75 and -115 dBc/Hz at 10-kHz and 1-MHz offsets, respectively, using a loop bandwidth of approximately 30 kHz. This 0.25-mm² PLL is fabricated in a 90-nm digital CMOS process and consumes 11 mW from a 1.2-V supply.