Dynamic Element Matching Approaches for Oversampling-Rate and Nyquist-Rate Data Converters
| Autor: | Da-Huei Lee, 李大輝 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Data converters have become very important building blocks for integrated circuits (ICs) due to the fast growth of digital signal processing systems recently. Lower cost high-performance data converters are strongly demanded to satisfy the requirements of more complicated system-on-a-chip (SOC) systems. Element mismatch is one of the major impairments for low-cost high-resolution data converters. Dynamic element matching (DEM) approaches have been widely used to suppress the harmonic distortions caused by element mismatches. In this dissertation, several DEM approaches are proposed and analyzed. For oversampling-rate data converters, advancing data weighted averaging (ADWA) is proposed to remedy baseband tone problems of conventional DWA. For Nyquist-rate data converters, random multiple DWA (RMDWA), random incrementing DWA (RIDWA) and randomized thermometer-coding (RTC) are proposed to achieve high spurious-free dynamic range (SFDR) and small maximum output error. Furthermore, an ultra low-cost Nyquist-rate current-steering digital-to-analog converter (DAC) is implemented to experimentally verify the proposed RTC. For oversampling-rate data converters, multibit sigma–delta modulators usually employ the DWA to suppress the element mismatch effect but are plagued by baseband tone problems. The existing DWA-like approaches for solving these problems are categorized in this dissertation as tone-suppressing and tone-transferring approaches. Although tone-transferring approaches can achieve a better signal-to-noise-plus-distortion ratio than tone-suppressing approaches, they may behave unfavorably for input signals with dc components. A flexible DWA-like approach, ADWA, which can achieve both tone-suppressing and tone-transferring functions, is proposed. Moreover, ADWA can be a reconfigurable approach that uses input signal detection schemes to set its configuration. For Nyquist-rate data converters, three DEM approaches are proposed to be used with a proper layout switching scheme in a proposed new DAC structure. RMDWA and RIDWA have randomization and consecutive selection properties. Randomization effectively suppresses harmonic distortions to achieve good SFDR. Consecutive selection obtains small static output errors when it is used with the presented rotated walk switching scheme. The third DEM approach proposed for Nyquist-rate DACs is RTC, which provides randomization, consecutive selection, and low element switching activity properties. In addition to the benefits of the proposed RMDWA and RIDWA, low element switching activity can achieve small dynamic errors caused by element switching. To experimentally verify the proposed RTC, a 14-bit ultra low-cost current-steering DAC is implemented in a 1P6M 0.18-μm 1.8-V CMOS process. The measured SFDR is up to 80dB for single-tone tests at a 10MHz sampling frequency. The measurement results show that the RTC can improve the SFDR by 16dB. The 14-bit current-steering DAC has an active area of less than 0.28-mm2. The active area of the DAC is smaller than those of the state-of-the-art DACs with 14-bit resolution. The active area of the DAC is also smaller than those of other published 12-bit and 10-bit DACs. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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