Introduction of Analog to Introduction of Analog to Digital ConverterDigital Converter

YZU EEVLSI Lab 3524Yan-Chu Chou

2 Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

OutlineOutline

IntroductionPrinciple

Structure

Conclusion

Reference

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

IntroductionIntroduction

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DigitalProcessor

Prefilter Sample/Hold Quantizer Encoder

General block diagram for an ADC

Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

Classification of ADC Classification of ADC ArchitecturesArchitectures

Conversion Rate Nequist ADCs Oversampled ADCsSlow Integrating(serial) Very high

resolution>14bits

Medium Successive approximation

1-bit PipelineAlgorithmic

Fast Flash Low resolution>6bits

Multiple-bit pipeline

Folding and interpolating

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

PrinciplePrinciple

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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 ConverterIntroduction of Analog to Digital Converter

Offset errorOffset error

Example of offset error for a 3-bit ADC5

Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

Gain errorGain error

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Example of gain error for a 3-bit ADC

Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

INL and DNLINL and DNL

Example of INL and DNL for a 3-bit ADC

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

Flash A/D ConverterFlash A/D Converter

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

Interpolating A/D Interpolating A/D ConverterConverter

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

ConclusionConclusion

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.

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Introduction of Analog to Digital ConverterIntroduction of Analog to Digital Converter

ReferenceReference

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.

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