Ring-Oscillator with Multiple Transconductors for Linear Analog-to-Digital Conversion

This paper proposes a new circuit-based approach to mitigate nonlinearity in open-loop ring-oscillator-based analog-to-digital converters (ADCs). The consists of driving current-controlled oscillator (CCO) with several transconductors connected parallel different bias conditions. current injected into the can then be properly sized linearize oscillator, performing inverse current-to-frequency function. To evaluate approach, circuit example has been designed 65-nm CMOS process, leading more than 3-ENOB enhancement simulation for high-swing differential input voltage signal 800-mVpp, considerable less complex design and lower power expected area comparison state-of-the-art based solutions. architecture also checked against PVT mismatch variations, proving highly robust, requiring only very simple calibration techniques. solution is especially suitable high-bandwidth (tens MHz) medium-resolution applications (10–12 ENOBs), such as 5G or Internet-of-Things (IoT) devices.