Analysis And Realization Of Low Power ADC For Biological Signal Acquisition

In modern society, the serious aging problem and increasing demandsfor medical services are pushing the traditional medical industry onto theway to changing. Personalized healthcare system is gaining more and moreattention with the rapid development of portable, intelligent medicalequipment. Biological signal acquisition systems are very important for themedical diagnostic and monitoring devices. In these kinds of systems,normally Analog-to-Digital Converter (ADC) is one of the most importantblocks. The operating characteristics of ADCs in biological signalacquisition systems are studied. Then this thesis mainly researches on howto realize a low-power and high-performance successive approximationregister (SAR) ADC using CMOS integrated circuit technology.This paper states the reason for choosing SAR ADC as one block ofthe bio-medical signal acquisition systems firstly. The basic architectureand working principle of SAR ADCs are emphasized in the followingsection. Differential architecture SAR ADC is adopted in this design. Thena comprehensive study is given covering every bock’s working principle,parameter index and architecture. According to the design principle of highaccuracy and low power, each sub-circuit is optimized in the designprocess. Finally SAR ADC’s pre-simulation results, layout andpost-simulation results are presented.This proposed SAR ADC is designed using TSMC0.18μm CMOS1P6M process. Post-simulation results show that this ADC achieves anENOB of9.76bits at a sampling rate of1kS/s with the standard supplyvoltage of1.8V. The power consumption is313.23nW and this ADC’smaximal DNL is0.4LSB while maximal INL0.6LSB. It also shows that this ADC’s SNDR is60.52dB, SNR is60.99dB and SFDR is72.16dB. Thesampling rate is1kS/s to30kS/s adjustable. Simulation results show thatthis proposed SAR ADC is suitable for low-power biological signalacquisition.