EE 230 Lecture 43 Spring 2010

EE 230 Lecture 43 Spring 2010 - EE 230 Lecture 43 Data...

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EE 230 Lecture 43 Data Converters Nonideal Effects
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Engineering Issues for Using Data Converters 1. Inherent with Data Conversion Process Amplitude Quantization Time Quantization (Present even with Ideal Data Converters) 2. Nonideal Components Uneven steps Offsets Gain errors Response Time Noise (Present to some degree in all physical Data Converters) How do these issues ultimately impact performance ? Review from Last Time:
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Nonideal Transfer Characteristics Uneven Steps X OUT X IN Ideal Transfer Characteristic Line Nonideal Transfer Characteristics of DAC X OUT X IN Ideal Transfer Characteristic Line Nonideal Transfer Characteristics of DAC Actual transfer characteristics can vary considerably from one device to another Review from Last Time:
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Nonideal Transfer Characteristics X OUT X IN Ideal Transfer Characteristic Line Nonideal Transfer Characteristics of DAC Uneven Steps This is termed a nonlinearity in the data converter Linearity metrics (specifications) include INL, DNL, THD and SFDR Review from Last Time:
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Integral Nonlinearity (INL) Often expressed in LSB: Linearity metrics: INL DNL THD SFDR { } 1 k INL max INL kN ≤≤ = LSB LSBF INL INL X = where () ( ) OUT OUT LSBF XN - X1 X= N-1 n LSB REF INL INL 2 X but ( ) OUT OUT REF LSBF n - X N-1 2 Review from Last Time:
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Integral Nonlinearity (INL) Linearity metrics: INL DNL THD SFDR { } 1 k INL max INL kN ≤≤ = n LSB REF INL INL 2 X What is an acceptable INL? INL IDEAL = 0 LSB What is the ideal INL? If INL<0.5LSB, it is generally considered acceptable This would be the quantization error for an n-bit ADC What is the INL of a DAC? Varies from part to part, often close to 0.5LSB, occasionally better, but often worse - Given in Data Sheet Review from Last Time:
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Differential Nonlinearity (DNL) Linearity metrics: INL DNL THD SFDR {} 1 k DNL max DNL kN <≤ = What is the IDEAL DNL of a DAC? 2 LSB REF DNL X n Ideal DNL =0 LSB What is an acceptable DNL of a DAC? If DNL<0.5LSB, it is generally considered acceptable What is the INL of a DAC? Varies from part to part, often close to 0.5LSB, occasionally better, but often worse - Given in Data Sheet Review from Last Time:
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Characterization of Nonlinearities Linearity metrics: INL DNL THD SFDR IN LK OUT IN LK OUT Linearity Metrics for ADC and DAC are Analogous to Each Other
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Integral Nonlinearity (INL) Linearity metrics: INL DNL THD SFDR
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Integral Nonlinearity (INL) Linearity metrics: INL DNL THD SFDR
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Integral Nonlinearity (INL) Linearity metrics: INL DNL THD SFDR What is the “gain” of an ideal ADC or an ideal DAC?
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This note was uploaded on 02/01/2012 for the course EE 230 taught by Professor Mina during the Fall '08 term at Iowa State.

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EE 230 Lecture 43 Spring 2010 - EE 230 Lecture 43 Data...

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