Design Of A 12-bit Dual Slope ADC For Wireless ECG Acquisition

Numerous studies have shown that ECG signals can reflect the physiological state of the heart and its internal tissues to a certain extent,and thus have been widely used as reference for the diagnosis of heart diseases and cardiovascular diseases.In recent years,people have paid more attention to personal health monitoring,compared with simple heart-rate-monitoring belts,smaller and wireless Electrocardiogram(ECG)equipment can be more well-used.This article is about the design of an analog-to-digital converter(ADC)in a wirelessly powered portable ECG monitoring system.This thesis first introduces the wirelessly powered ECG system,and clarifies the conditions and requirements that provided to the ADC.Then,combined with the characteristics of different ADC and current research on ECG chips,the dual-slope integral ADC architecture is selected for reasons of low power,medium resolution,low speed and considering the process we use.Next,the basic structure and working principle of the dual-slope ADC are introduced,design requirements and the performance of ADC are summarized.Design considerations and circuit structure selection of each sub-module in ADC are introduced in detail,and the design of each submodule including sample-and-hold circuit,integrator,comparator and digital control part is completed according to system requirements.Solutions to improve and optimize the existing problems has been proposed.Finally,the simulation results are given.The proposed 12-bit dual-slope ADC is implemented in 0.35-μm CMOS process,the ADC has sampling rate of 689S/s under 6MHz clock,working at 2-V supply voltage,the ADC consumes 6-μA current.Simulation result shows that the effective number of bits(ENOB)for the ADC is 11.8bit at low input frequency of 35.0055 Hz.