A Pseudo-Virtual Ground Feedforwarding Technique Enabling Linearization and Higher Order Noise Shaping in VCO-Based ΔΣ Modulators

This article presents a third-order voltage-controlled oscillator (VCO)-based analog-to-digital converter (ADC) that leverages pseudo-virtual ground (PVG) feedforwarding (FF), linearizing the VCOs and enabling higher order noise shaping with a single feedback digital-to-analog converter. This technique leads to a power-efficient ADC implementation with a wide dynamic range. The ADC is fabricated in a 65-nm process and achieves a 92.1-dB SNDR in a 2.5-kHz bandwidth. This results in a state-of-the-art 179.6-dB figure-of-merit (FoM) among previously published VCO-based ADCs. The PVG FF technique allows the ADC to attain extremely high linearity, 123-dB peak SFDR, with a wide 1.8-Vpp differential input range. The ADC maintains performance with up to 200-mV variation on the 0.8-V supply and across temperatures from 0 to 70 °C.