Custodio José R, Goes João, Paulino Nuno, Oliveira João P, Bruun Erik
Department of Electrical Engineering (DEE), Faculty of Sciences and Technology (FCT) and the Centre of Technology and Systems (CTS), Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
IEEE Trans Biomed Circuits Syst. 2013 Jun;7(3):376-85. doi: 10.1109/TBCAS.2012.2203819.
This paper describes the design and experimental evaluation of a multibit Sigma-Delta (ΣΔ) modulator (ΣΔM) with enhanced dynamic range (DR) through the use of nonlinear digital-to-analog converters (DACs) in the feedback paths. This nonlinearity imposes a trade-off between DR and distortion, which is well suited to the intended hearing aid application. The modulator proposed here uses a fully-differential self-biased amplifier and a 4-bit quantizer based on fully dynamic comparators employing MOS parametric pre-amplification to improve both energy and area efficiencies. A test chip was fabricated in a 130 nm digital CMOS technology, which includes the proposed modulator with nonlinear DACs and a modulator with conventional linear DACs, for comparison purposes. The measured results show that the ΣΔM using nonlinear DACs achieves an enhancement of the DR around 8.4 dB (to 91.4 dB). Power dissipation and silicon area are about the same for the two cases. The performance achieved is comparable to that of the best reported multibit ΣΔ ADCs, with the advantage of occupying less silicon area (7.5 times lower area when compared with the most energy efficient ΣΔM).
本文描述了一种多位Σ-Δ调制器（ΣΔM）的设计与实验评估，该调制器通过在反馈路径中使用非线性数模转换器（DAC）来提高动态范围（DR）。这种非线性在动态范围和失真之间形成了一种权衡，这非常适合预期的助听器应用。这里提出的调制器采用了全差分自偏置放大器和基于全动态比较器的4位量化器，该比较器采用MOS参数预放大以提高能量和面积效率。采用130nm数字CMOS技术制作了一个测试芯片，其中包括所提出的带有非线性DAC的调制器以及一个带有传统线性DAC的调制器，用于比较。测量结果表明，使用非线性DAC的ΣΔM实现了约8.4dB的动态范围增强（达到91.4dB）。两种情况下的功耗和硅面积大致相同。所实现的性能与已报道的最佳多位ΣΔ模数转换器相当，其优势在于占用的硅面积更小（与最节能的ΣΔM相比，面积低7.5倍）。
