Research And Design Of 16-channel 12-bit SAR ADC With R-C Architecture

With the boom of multimedia market and Electronic science and technology,digital technology is developing rapidly.However,most of the nature signals are analog signals,like temperature?pressure?sound and speed.Thus ADC(Analog-to-Digital Converter)is needed to convert analog signals to digital signals.MCU is the singlechip we usually used(Microcontroller Unit).It integrates CPU?RAM(ROM)?counter and I/O in one chip.SAR ADC has a good performance in medium speed and medium accuracy field,like 8?16bits and lower than 5MS/s?In nowdays CMOS process,SAR ADC can be designed in small chip area with lower power,and has comprehensive advantage in many aspacts like speed?accuracy?cost and power dissipation.Especially,it is suitable to be the connector of MCU.To improve the efficiency of MCU,the ADC should process the nature signals as much as possible with small area.In this paper,a 16-channel SAR ADC,consisted of DAC?comparator and SAR logic,is designed.According to the need of application,DAC with R-C construction is used,we aim to use a thermometer code only for the most significant bits.And the resistor array acts as a 7-bit Sub-DAC to increase resolution and to avoid a large capacitor array.Moreover,special switching control circuits and sample mode are described to avoid short circuit and charge injectio.Three preamplifiers are used to have a sufficient gain.Automatic offset cancellation is designed in this comparator to get a more accurate result.A 16-channel 12-bit SAR ADC is realized in 130 nm GSMC technology.Simulated at 3.3 V analog supply voltage,1.5 V digital supply voltage reference and 1Msample/s,The layout design has been finished and the area of the ADC is 626*558 ?m2.the text results show that in single-ended mode,therer are 70 missing codes,and DNL=+4.1/-1 LSB,INL=+13/-2.5 LSB,SNR=64.49 dB,SNDR=55.19 dB,ENOB=8.87 bit,in double-ended mode,therer are 130 missing codes,DNL=+1.7/-1 LSB,INL=+4.3/-6.1 LSB,SNR=63.05 dB,SNDR=51.48 dB,ENOB=8.26 bit?The test result is a bit different from the simulation,this paper analyzes the reason at last.