A 0.9-to 8-GHz VCO with a differential active inductor for multistandard wireline SerDes

This study demonstrates a wide frequency tuning range LC voltage-controlled oscillator (LC-VCO) with an active inductor in a 90-nm CMOS process. As the proposed LC-VCO is intended to be extremely flexible without redesign for several new-generation SerDes interfaces, a wide operating frequency makes the phase-locked loop (PLL) applicable to the multistandards. To demonstrate a highly competitive design, a quality (Q) factor enhancement technique has been also demonstrated to reduce the loss from the active inductor, leading to an appropriate phase noise over the entire tuning range. At a supply of 1.2 V, the fabricated LC-VCO provides a frequency tuning range of 0.9-8 GHz (160%) with power consumption of 3.2-19.1 mW. The measured phase noise is from-105 to-118 dBc/Hz at a 1-MHz offset. Realized in a fully integrated PLL chip, it occupies an active area of 0.08 × 0.16 mm².