A 12b 50MS/s fully differential zero-crossing-based ADC without CMFB

Abstract

As intrinsic device gain and power supply voltages decrease with CMOS technology scaling, it is becoming increasingly challenging for designers of conventional opamp-based switched-capacitor circuits to meet gain and output swing targets, and to ensure stability. Zero-crossing based circuits (ZCBC) are presented as an alternative architecture where each opamp is replaced with a current source and a zero-crossing detector. This changes the dynamics of the system while preserving the functionality. To further improve the robustness of ZCBC designs, we present a 50MS/s, 12b ZCBC pipelined ADC with fully differential signaling and automatic offset compensation.