A Mostly Digital VCO-Based CT-SDM With Third-Order Noise Shaping

作者：Babaie Fishani Amir; Rombouts Pieter

来源：IEEE Journal of Solid-State Circuits, 2017, 52(8): 2141-2153.

DOI：10.1109/JSSC.2017.2688364

• Analog-to-digital converter (ADC)
• low-voltage design
• quantization noise shaping
• ring oscillator
• sigma-delta modulator
• time-domain signal processing
• voltage-controlled oscillator (VCO)

This paper presents the architectural concept and implementation of a mostly digital voltage-controlled oscillator-analog- to-digital converter (VCO-ADC) with third-order quantization noise shaping. The system is based on the combination of a VCO and a digital counter. It is shown how this combination can function as a continuous-time integrator to form a high-order continuous-time sigma-delta modulator (CT-SDM). The counter consists only of digital building blocks, and the VCOs are implemented using ring oscillators, which are also digital-friendly. No traditional analog blocks, such as opamps, OTAs, or comparators, are used. As a proof of concept, we have implemented a third-order VCO-based CT-SDM for a 10-MHz bandwidth in the low-power version of a 65-nm CMOS technology. This prototype shows a measured performance of 71/66.2/62.5-dB DR/SNR/SNDR at a 10-MHz bandwidth while consuming 1.8 mW from a 1.0-V analog and 1.9 mW from a 1.2-V digital supply. With digital calibration, the nonlinearity could be pushed below the noise level, leading to an improved peak SNDR of 66 dB.

• 出版日期2017-8