High Precision And Low Power Audio Sigma-delta Modulator Design

Radio With the rapid development of the deep submicron technology in integrated circuit,system integration is extended over many areas.Particularly,SOC(system-on-chips) integration becomes a momentous issue for potable audio and wireless communication fields. Hence,research trend is in progress toward design minimizing power consumption with high performance.Especially,for the audio applications,ADCs restrict major system performance. Today,the performance of an audio ADC becomes substantial for portable media players and MEMS(Micro-Electro- Mechanical System) silicon microphones.Depending on battery power and the quality of sound,the market demands on ADC design challenges toward power savings and high resolutions.Aim at the demand of the market,the design of a 0.9V 16bit audio Sigma-Delta modulator is researched in this thesis.After introducing the principle of Sigma-Delta technique,the stability chatacteristics and noise of Sigma-Delta,the emphasis of analysisi and research turns to system design,circuit design,layout design.In system design, third-order single-loop forward-feedback one-bit structure is applied in this thesis.In the circuit design,the improved bootstrap switch and improved bias circuit for the Operational Transconductance Amplifier(OTA) is presented,and two-stage OTA with high output swing and low power is applied,and clock boost is designed to let the swtich on.Implemented in SMIC 0.18-μm one poly six metal CMOS Mixed-Signal process,the die occupies an area of 0.42 mm2,consuming about 300μW power.Under the exist test condition,with 0.9V power supply,5.632MHz clock freauency,the input signal of 1V Vp-p in the 22KHz audio bandwidt,the noise floor is -91.49dB,SNDR is 80.86dB,without the power of the second and third harmonic wave.