A 64-fJConv-Step Continuous-Time Modulator in 40-nm CMOS Using Asynchronous SAR

Abstract

A third-order single-loop continuous-time sigma- delta modulator (CTSDM) with 6-bit asynchronous successive approximation register (ASAR) quantizer and digital trun- cator for WCDMA/GSM/EDGE cellular systems is presented. The proposed ASAR-based quantizer reduces the area and power of the modulator dramatically by ut ilizing the digital truncation technique. By using the 6-bit ASAR quantizer, the sampling frequency is lowered, which reduces the design efforts not only in system level but also in