The Design Of16Bit Audio Sigma-delta Modulator

Digital circuits are widely used in various fields such as communications, video,however the signals in nature are analog signals, analog-to-digital converter as a bridge toconnect the analog and digital domains, the performance of the analog-to-digital converteris particularly important. Sigma-delta ADC widely used in the audio field as its highaccuracy, simple structure，not require strict component matching.The key in the design ofaudio Sigma-delta modulator is that maintain high accuracy while reducing powerconsumption..The paper design a16bit audio Sigma-delta modulator with chrt180process,1.8Vsupply voltage. The paper aim at maintain the accuracy while reducing power consumption.In order to reduce power consumption, in the system design,first select the topology of lowpower consumption； then select the feedforward structure that have a lower powerconsumption compare with feedback structure；at last through SDtoolbox of matlab estimatethe power consumption of the four scheme that realize the accuracy target,and choose thelowest power consumption scheme,ultimately determine the design uses a fourth-ordersingle-loop one bit quantizer structure, over-sampling rate is64. In the circuitimplementation, the op amp is the core of the modulator system, and also consume the mostpower. The paper present a new low power symmetric folded cascode amplifier. Theproposed amplifier delivers the same performance as that of the conventional symmetricfolded cascode amplifier while consuming only50%the power, and the power consumptionis100uW. The modulator system overall power consumption is600uW, While themodulator system that use traditional symmetric folded cascode amplifier powerconsumption is1mW. In the modulator system, reference voltage as the output of the DACis feed back to the signal input terminal control by switch, so the reference voltage powersupply rejection ration directly affect the accuracy of the system, In order to ensure theaccuracy of the modulator, the voltage reference low-frequency power supply rejectionration increase by60db through the Low Dropout Regulator.