A 1.2V 64fJ/Conversion-Step Continuous-Time ∑△ Modulator Using Asynchronous SAR Quantizer and Digital △∑ Truncator

摘要

A 3~(rd)-order single-loop continuous time sigma-delta modulator (CTSDM) with 6-bit asynchronous SAR quantizer and digital delta-sigma truncator for WCDMA/GSM/EDGE cellular systems is presented. The proposed asynchronous SAR based quantizer reduces the area and power dramatically with the help of digital truncation technique. In addition, the modulator incorporating the proposed operational amplifiers (op-amp) with ac coupled push-pull stage is to improve the high frequency driving capability. The modulator sampling at 65MHz achieves 83.4dB dynamic range (DR) and 80/79.6dB peak SNR/SNDR with 1.92MHz bandwidth (BW) in WCDMA mode. In GSM/EDGE mode, the DR is 96.2 dB. Implemented in 40nm CMOS, the modulator occupies 0.051mm~2 and consumes 1.91mW from a 1.2V supply. A 64fJ/conversion figure of merit (FOM) is achieved.