PWM模拟DAC的关键参数分析

Key parameters analysis of DAC using PWM

PWM模拟DAC技术由于其价格便宜、技术简单在低成本嵌入式系统中应用广泛,然而其性能指标却无法与集成的DAC相比。建模讨论了影响PWM模拟实现DAC系统的性能的主要因素。仿真发现,滤波器环节对于PWM模拟DAC的性能参数是至关重要的,在不考虑PWM的位数限制时,滤波级数越高DAC精度越高,然而DAC的建立时间也会显著增加。分析发现,这两个主要参数分别取决于滤波系统对于高频成分的频率响应和对于直流分量的阶跃响应。具体应用中应该权衡DAC精度和转换速度,以确保应用PWM模拟DAC可以满足具体应用需求。

DAC （Digital-to-Analog Converter） using PWM （Pulse Width Modulation） technology is widely used in low cost embedded systems due to cheap price and simple to use, however its performance index cannot match the real DAC. In this paper, models are built to discuss the main factors which affect the performance of PWM imitated DAC system. Through simulation it finds that the filter plays a key role in the DAC, without considering the digits limit of PWM, the higher the filter series the more accurate the DAC is, however, the establishment time of the DAC will increase significantly. Through analysis it finds that the two main parameters depend on the high frequency response and DC step response of the filtering system respectively. In specific applications, the precision and transformation speed of the DAC should be carefully weighed to meet specific requirements.