Introduction of Analog to Digital Converter YZU EE VLSI Lab 3524 Yan-Chu Chou

2 Introduction of Analog to Digital Converter Outline  Introduction  Principle  Structure  Conclusion  Reference 1

Introduction of Analog to Digital Converter Introduction 2 Digital Processor PrefilterSample/HoldQuantizerEncoder General block diagram for an ADC

Introduction of Analog to Digital Converter Classification of ADC Architectures Conversion RateNequist ADCsOversampled ADCs SlowIntegrating(serial)Very high resolution>14bits MediumSuccessive approximation 1-bit Pipeline Algorithmic FastFlashLow resolution>6bits Multiple-bit pipeline Folding and interpolating 3

Introduction of Analog to Digital Converter Principle 4 Static Characterization of ADCs Offset error:the horizontal difference between this line and the infinite resolution characteristic that passes through the origin Gain error:a difference between the actual characteristic,and the infinite resolution characteristic,which is proportional to the magnitude of the input voltage Integral nonlinearity(INL):the maximum difference between the actual finite resolution characteristic and the ideal finite resolution characteristic measured vertically in percent or LSBs Differential nonlinearity(DNL):defined as a measure of the separation between adjacent codes measured at each vertical step in percent or LSBs

Introduction of Analog to Digital Converter Offset error Example of offset error for a 3-bit ADC 5

Introduction of Analog to Digital Converter Gain error 6 Example of gain error for a 3-bit ADC

Introduction of Analog to Digital Converter INL and DNL Example of INL and DNL for a 3-bit ADC 7

Introduction of Analog to Digital Converter Flash A/D Converter 8

Introduction of Analog to Digital Converter Interpolating A/D Converter 9

Introduction of Analog to Digital Converter Conclusion The ADC by nature must be sampled. It is not possible to continuously convert the incoming analog signal to a digital output code. The ADC is a sampled-data circuit. 10

Introduction of Analog to Digital Converter Reference  Phillip E. Allen,Douglas R. Holberg, ”CMOS Analog Circuit Design,”Second Edition.  David A. Johns Ken Martin,”Analog Integrated Circuit Design,”John Wiely & Sons,Inc. 11