Design Of SAR ADC For The Monolithic Integrated Sensors

With the rapid development of CMOS integrated circuit technology and MEMStechnology,the monolithic integration of sensor and signal processing circuit has becoming a major development trend.And the ADC is the interface of analog to digital,is the core module of the monolithic integrated circuit.Analog-to-digital converters must have the characteristic such as slow power consumption and small area to meet the requirements of high monolithic integrated circuits.This paper designs a 10-bit fully differential successive approximation analog-to-digital converter(SAR ADC)for In As sensor monolithic integrated circuits.The analog-to-digital converter consists of digital-to-analog converters(DAC),comparator,successive approximation registers,control logic circuits.DAC makes the improvement based on the "Vcm-based" switching method,saves the highest bit capacitance.The DAC uses 6MSB + 3LSB segmented charge proportional scaling structure,effectively reducing the overall area and improving the ADC accuracy.In terms of layout design,The capacitor array uses the common centroid symmetry structure to improve the matching of the capacitors.The circuit is designed with CSMC0.5?m2P3M process.Its spurious-free dynamic range(SFDR)is 67.8d B and the effective number of bits(ENOB)is 9.53 bit with in the 100KS/s sample rate and 0.49 KHz input signal frequency,The ADC area is 700?m×610?m,and its power consumption is 963.5?W.Compared with the traditional charge redistribution ADC the power consumption decreased by 69%.This ADC meets the design requirements.