| Digital-to-analog Convertor (DAC), based on∑-△noise-shaping and over-sampling tech-niques, can convert digital signal to high resolution analog signal reliably. It has many advantages in converting, such as the ultimate low mismatch, high reliability and being able to embed to other SOC as an IP- core module. The more important is its high resolution and dynamic range compar-ing to other DAC structures. Therefore, it is widely used in high-resolution measurements, audio converting, car electronics, and other fields.It is difficult to design and implement a high-order∑-△modulator due to the non-linearity and the non-stability. Based on a synthesis of many empirical principals and methods from refer-ences, the basic principles of∑-△modulator is described in this paper at first. And the design flow of modulator with common structure is discussed. Then, a design flow of stable, high-order and high-resolution modulator is proposed. The performance parameters of such modulator design scheme are specified according to the market requirement. Based on the scheme, a 16-bit resolu-tion, full-scale input range and three-order 128 over-sampling modulator design is accomplished in this paper.∑-△structure is adopted in this paper, the quantization bit, oversampling ratio and order of the modulator are determined following the system requirement. Six bit quantization, three-order single-loop structure modulator is implemented after a deep stability analysis of high-order sin-gle-loop modulator. This design has been implemented and verified on the Cyclone FPGA plat-form, with the real-time audio signal verification. Testing results indicates that the SNR of the de-signed DAC module's output signals meets the resolution requirement in 16-bit data-convention application, possessing favorable compatibility and universal ability also.The DAC module developed in this paper could be reused as an IP core in other SOC systems, holding strong application performance and innovation. |
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