A Novel MIM-Capacitor-Based 1-GS/s 14-bit Variation-Tolerant Fully-Differential Voltage-to-Time Converter (VTC) Circuit

Abstract

Time-based Analog-to-Digital Converter (TADC), plays a major role in designing Software-Defined Radio (SDR) receivers, at scaled CMOS technologies, as it manifests lower area and power than conventional ADCs. TADC consists of 2 major blocks. The input voltage is converted into a pulse delay using a Voltage-to-Time Converter (VTC). In additions, the pulse delay is converted into a digital word using a Time-to-Digital Converter (TDC). In this paper, a novel fully-differential VTC based on a new methodology is presented which reports a highly-linear design. A metal-insulator-metal (MIM) capacitor as well as a dynamic calibration technique based on a set of large-sized capacitor-based voltage dividers circuits are utilized to automatically compensate the Process-Voltage-Temperature (PVT) variations. Moreover, the layout design is introduced. The proposed design operates on a 1[Formula: see text]GS/s sampling frequency with a supply voltage of 1.2[Formula: see text]V. After calibration, simulation results, using TSMC 65[Formula: see text]nm CMOS technology, report a 1.42[Formula: see text]V wider dynamic range due to the differential mechanism with a 3% linearity error. This design achieves a resolution up to 14 bits, a 0.07 fJ/conversion FOM, a 229[Formula: see text][Formula: see text]m2 area and a 0.25[Formula: see text]mW power. The simulation results are compared to the single-ended VTC results and the state-of-the-art analog-part ADCs results to show the strength of the proposed design.