A high quality factor bulk-CMOS switch-based digitally programmable RF capacitor

A digitally programmable capacitor in bulk-CMOS technology is demonstrated. Based on a 130 nm standard bulk-CMOS process of Infineon, this circuit uses switched metal-insulator-metal (MIM) capacitances to vary the capacitance. Using 6 bits, the capacitor can be digitally programmed from 1 to 10 pF in 160 fF steps in the radio frequency (RF) range up to 2.7 GHz and shows a maximum quality factor of 88 at 1 GHz at a tuning ratio of 10. The size of the chip, including the charge pump, 1.8 V to 3.6 V voltage regulator and digital MIPI control interface, is 1256 × 856 µm². The circuit draws a current of 75 µA at 2.8 V supply voltage.