Design And Implementation Of Low Voltage Audio ΔΣDAC

Different fields have different requirements on the D/A Converters, because of the rapid development of multimedia technology in the audio field, portable audio electronics with the characteristic of light, thin, short, small require high precision and high efficiency D/A conversion at low voltage. Digital CMOS process is widely used because of its low cost and easy large-scale integration, and has become the mainstream process, so it is better to finish the design of the audio DAC in the standard digital CMOS process.This paper presents the design and implementation of a low voltage audio AE DAC. Firstly, the basic audio AE DAC structure and key technologies are discussed, and then the design and implementation of all parts of the audio AE DAC are illustrated in detail, including the design and implementation of interpolation filter, AE modulator, DLPF encoder and digital class D amplifier. At last, the measurement results are presented and analyzed.To get high precision performance, the existing audio AE DAC structures always have high power dissipation or high complexity. We proposed the architecture with DLPF encoder to overcome the weaknesse according to the statistical properties of the audio signal amplitude, the DLPF encoder is completed with simple digital logic circuit. The output PDM signals of ΔΣ modulator is encoded by the DLPF encoder, and then control the digital class D amplifier, which can reduce the power output stage switching losses and improve the output signal to noise ratio.Digital class D amplifier is a key partt of this design, the main factors which impact the performance of digital class D amplifier are analyzed, and the structure of the class D amplifier is presented. In order to achieve higher power efficiency, the structure and the size of power output stage transistors are designed carefully, the layout of power output stage transistors adopt the waffle-type structure.The design is fabricated in0.18μm standard CMOS process, measurement shows that the AE DAC can work at the voltage of0.8V～1.8V, achieves83.9dB peak SNDR and91.9dB dynamic range (DR), the THD is less than-84.8dB and the power efficiency achieves95%with a360Ω load. The die area is1.875mm×1.490mm.