A zero-crossing based 12b 100MS/s pipelined ADC with decision boundary gap estimation calibration

This paper describes a 12-bit zero-crossing based pipeline 100-MS/s ADC. The prototype ADC, fabricated in a 90-nm CMOS process, occupies 0.32 mm². The capacitor mismatch is calibrated by decision boundary gap estimate algorithm that runs in the background. It achieves an ENOB of 10.2 bits for a 49 MHz input signal and dissipates 6.2 mW from a 1.2V supply for a FOM of 53fJ/step.

Introduction

Zero-crossing based (ZCB) circuits were introduced as a lower power alternative for switched capacitor circuits [1]. Power hungry Op-amps are replaced by a zero-crossing detector and current sources. In this work, a number of improvements have been made in the circuit design to make the converter faster and more accurate. In addition, digital calibration based on Decision Boundary Gap Estimation [2] is added to correct capacitor mismatch.