A 99.1-dB SFDR, 87.1-dB SNDR, 50-kS/s 3rd-Order Continuous-Time Incremental ADC With Current-Controlled-Oscillator Quantizer

Abstract

This brief presents a $3{^{\text {rd}}}$ -order continuous-time (CT) incremental ADC that uses a pseudo-differential current-controlled-oscillator quantizer (CCOQ). The approach combines the complementary aspects of CCO-based quantization and incremental ADC operation. The CCOQ, used as a frequency quantizer, improves the efficiency of high-order incremental operation as it provides multi-bit quantization, intrinsic dynamic element matching, and an additional order of residual accumulation. At the same time, the CCOQ conveniently does not require reset in the analog domain, thus simplifying oscillator design. A prototype IC was fabricated in 180nm CMOS process. Clocked at 3.2 MHz with a Nyquist sampling rate of 50 kHz, based on measurements it achieves 87.1 dB SNDR, 99.1 dB SFDR, and 89.7 dB DR and consumes 204 $\mu $ W at 1.4V supply. This results in a competitive 168 dB SNDR-based Schreier FoM, and it demonstrates the potential for leveraging CCOQ benefits within an IADC topology.