The CMOS circuit implementations for a Sigma Delta modulator with element mismatch averaging feedback switched-capacitor circuit
| Autor: | Wei-chih Hung, 洪偉智 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 In the thesis, we will present the CMOS circuit design and implementation of a multi-bit Sigma-Delta modulator (SDM). For multi-bit SDM, it also needs a multi-bit digital to analog converter (DAC) in the SDM architecture. When the DAC exists the element mismatch problem, the linearity of DAC will be reduced,the dynamic range (DR) of SDM will be degraded. One of the solutions is to use dynamic element matching (DEM) to solve the linearity problem from DAC element mismatch. However, when the quantizer bit in the SDM is increasing, the complexity of DEM circuit is also ncreasing. The thesis will also propose a new element mismatch averaging techniquea DAC circuit with switched capacitor averaging (SCAV) technique for the feedback DAC circuit implementation to relax the component mismatch issue and circuit complexity for a multi-bit DAC..The SDM is designed as single-stage with feed-forward structure with 3-order loop filter and 3-bit internal quantizer. The SDM is fabricated in a 0.18μm CMOS process. At sampling frequency of 46.08-MHz, supply voltage of 1.8V, oversampling ratio (OSR) of 12, the signal to noise-plus-distortion ratio (SNDR) of the proposed SDM can achieve to 12-bit resolution. The thesis proposes a new element mismatch averaging technique for the feedback switched-capacitor digital-to-analog converter implementation to relax the component mismatch issue for a multi-bit SDM. The SDM is fabricated in a TSMC 0.18μm CMOS process.At sampling frequency of 46.08-MHz, supply voltage of 1.8V, oversampling ratio (OSR) of 12, the signal to noise-plus-distortion ratio (SNDR) of the proposed SDM can achieve to 66dB. Even existing 5% mismatch for the capacitors of DAC, the SNDR also can reach 61dB. chip area including boding pads 1.038×0.823 mm2. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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