基于过采样Σ-Δ噪声整形的16位DAC设计和VLSI实现

【作者】 邓彦松；

【导师】 陈天麒； 邹铮贤；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2005， 硕士

【摘要】 Σ-Δ转换器技术是基于过采样噪声整形的数据转换技术,非常适合用于高精度数据转换器结构。以Σ-Δ转换器技术为基础的转换器相比于其他类型的D/A 转换器有很多先进之处,其最主要的优势在于采用了较简单的模拟电路结构,因此其成本可以持续下降,同时其数字化特性可以使之集成到其它的数字芯片中,其工艺不具有特殊性。Σ-Δ转换器固有的线性以及对差分非线性和背景噪声的不敏感特性,使得系统的信噪比可以做得很高。在实现高精度数据转换器的设计中,至少在成本方面,基于过采样和Σ-Δ噪声整形的结构具有无以伦比的优势。当然Σ-Δ调制器并不是完美的,1bit 高阶调制器的不稳定性就是它一个软肋。本文讨论了实现稳定的1bit 高阶调制器的方法,并且实现了稳定的5阶调制器,其信噪比可以达到120dB 以上。本论文主要论述基于过采样和Σ-Δ噪声整形的16 位立体声音频DAC 的系统设计及模拟前端结构设计,它采用Σ-Δ转换技术来实现90dB 的实际信噪比。其中系统设计包括对调制器结构的选取,调制器阶数和过采样比的确定,稳定性分析以及系统零点优化等等;模拟前端电路设计包括CMOS 模拟运算放大器的原理及设计、开关电容积分器、带隙基准源的原理及设计等等,同时还给出上述基本构成元件的设计要求以及相关的注意事项及原理分析;本文的实现部分还给出了该芯片的后端版图实现。通过电路系统仿真以及芯片流片验证,可以达到90dB的信噪比,芯片面积仅有2.7mm~2,功耗25mW。芯片已经形成IP,可以单独流片,也非常适合在SOC 中应用。更多还原

【Abstract】 Sigma-Delta conversion technology is based on oversampling, noise shaping.There are many inherent advantages in S-D based digital to analog converters. Themajor advantage being that it is based predominantly on digital signal processing,hence the cost of implementation is low and will continue to decrease. Also, due to itsdigital nature S-D converters can be integrated onto other digital devices.Manufacturing technology notwithstanding, S-D technology offers system costsavings because the analog filter requirements are considerably less complexion. S-Dconverters are inherently linear and don’t suffer from appreciable differentialnon-linearity, and the background noise level which sets the system S/N ratio isindependent of the input signal level. The last, but certainly not least, consideration iscost. Attaining a high level of performance at a fraction of the cost of hybrid andmodular designs is probably the greatest advantage of all. SDM is good, but notperfect.In this paper, a complete analog front end for low frequency measurementapplications is presented. The part can accept a serial digital word directly from atransducer and outputs analog signals. It employs a sigma-delta conversion techniqueto realize up to 90dB SNR. The basic specification and general measurement arediscussed. The mechanism of oversampling converters with Sigma-delta modulator isdiscussed. Systematic design is carried out and presents the specific parameterindexes according to the characteristics, basic functions and the related requirementsof the chip. Then goes on with the design and realization of the ananlog circuits.CMOS opamp and Switched-Capacitor filters is discussed, In the end, the layoutdesign is shown.更多还原