Performance of Si-Integrated Wide-Band Single-Ended Switched Capacitor Arrays

A closed-form equation for the quality factor of CMOS or BiCMOS single-ended switched capacitor arrays (SSCAs), intended for radio-frequency (RF) and microwave switched tuning resonators, is presented and analyzed. This expression predicts accurately the SSCA quality factor (Qssca) with respect to the operation frequency and tuning control input. Important results arise from this equation, viz., Qssca shows a strong dependence on the reference cell electric parameters, presents a monotonically behavior with the tuning control input, is independent of the SSCA size (number of cells) and increases as the technology scales down. Besides that, new concepts are also introduced, namely, basic switch, reference switch, reference capacitor and reference cell. A 0.1 to 6 GHz SSCA, designed with standard 0.35 mum 2-poly 4-metal mixed-signal CMOS technology, is also described. The SSCA has a capacitive tuning range from 210 to 385 fF with a resolution capacitance of 25 fF. The theoretical results, obtained with the SSCA model, match the SSCA layout Spectre^reg RF simulation.