设计了一种应用于音频Codec的高精度Sigma-Delta DAC,针对数字插值滤波器占用面积大的问题,提出了乘法器复用的方法,减少数字电路的硬件消耗.为解决Sigma-Delta调制器多比特量化引起的非线性问题,引入DWA(Data Weight Average)算法,提高系统的精度.此外,DCT(Direct Charge Transfer)电路用于实现数字域到模拟域的高精度转换.电路采用0.18μm CMOS工艺,整体DAC的信噪比为105.7dB@1 150Hz,有效位数达到17.26bit.
A high-precision Sigma Delta DAC for audio Codec has been designed.To address the issue of large area occupied by digital interpolation filters,a multiplier multiplexing method has been proposed to reduce hardware consumption in digital circuits.To solve the nonlinear problem caused by multi bit quantization in Sigma Delta modu-lators,the DWA(Data Weight Average)algorithm is introduced to improve the accuracy of the system.In addition,DCT(Direct Charge Transfer)circuits are used to achieve high-precision conversion from digital domain to analog domain.The circuit adopts 0.18 μ m CMOS process,and the overall signal-to-noise ratio of the DAC is 105.7dB@1 150Hz.The effective number of bits reaches 17.26 bit.