Open Access

ARTICLE

A 78-MHz BW Continuous-Time Sigma-Delta ADC with Programmable VCO Quantizer

Sha Li^1,2, Qiao Meng^1,*, Irfan Tariq¹, Xi Chen³

1 Institute of RF- & OE-ICs, Southeast University, Nanjing, 210096, China
2 Jiangsu Key Construction Laboratory of IoT Application Technology, Wuxi Taihu University, Wuxi, 214064, China
3 Polytechnic University of Madrid, Madrid, 28031, Spain

* Corresponding Author: Qiao Meng. Email:

Computers, Materials & Continua 2022, 72(3), 6079-6090. https://doi.org/10.32604/cmc.2022.027404

Received 17 January 2022; Accepted 04 March 2022; Issue published 21 April 2022

Abstract

This article presents a high speed third-order continuous-time (CT) sigma-delta analog-to-digital converter (SDADC) based on voltage-controlled oscillator (VCO), featuring a digital programmable quantizer structure. To improve the overall performance, not only oversampling technique but also noise-shaping enhancing technique is used to suppress in-band noise. Due to the intrinsic first-order noise-shaping of the VCO quantizer, the proposed third-order SDADC can realize forth-order noise-shaping ideally. As a bright advantage, the proposed programmable VCO quantizer is digital-friendly, which can simplify the design process and improve anti-interference capability of the circuit. A 4-bit programmable VCO quantizer clocked at 2.5 GHz, which is proposed in a 40 nm complementary metal-oxide semiconductor (CMOS) technology, consists of an analog VCO circuit and a digital programmable quantizer, achieving 50.7 dB signal-to-noise ratio (SNR) and 26.9 dB signal-to-noise-and-distortion ration (SNDR) for a 19 MHz − 3.5 dBFS input signal in 78 MHz bandwidth (BW). The digital quantizer, which is programmed in the Verilog hardware description language (HDL), consists of two-stage D-flip-flop (DFF) based registers, XOR gates and an adder. The presented SDADC adopts the cascade of integrators with feed-forward summation (CIFF) structure with a third-order loop filter, operating at 2.5 GHz and showing behavioral simulation performance of 92.9 dB SNR over 78 MHz bandwidth.

---

Keywords

---