Download - Why Data Conversion?
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Why Data Conversion?• Real world is analog• Mostly, communication and computation is digital• Need a component to convert analog signals to digital (ADC) and convert the processed digital signal back to analog (DAC)
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Types of Data Converters
• Niquist rate data converters• Serial• Successive approximation• Flash
• Oversampling (Sigma-Delta)
• Power consumption• Area consumption• Operating speed • Conversion time (delay)• Error (Linearity)• Noise performance• And many more….
How is a data converter characterized ???
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Ideal DAC/ADC characteristics
DAC ADC
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Integral Non-Linearity Error
INL: Deviation of the code transition from its ideal location
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Differential Non-Linearity Error
DNL: Deviation of the code width from 1 LSB
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Full Scale Error
Full scale error: Difference between the actual value that triggers the transition to full-scale and the ideal analog full-scale transition value
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Gain Error
Gain error: Difference between the slope of an actual transfer function matches the slope of the ideal transfer function
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Noise Performance
SNR (signal to noise ratio): Ratio of the fundamental signal to the noise spectrum.
THD (total harmonic distortion): Ratio of the fundamental signal tothe noise spectrum.
SFDR (spurious free dynamic range): Ratio of the fundamental signal and the highest spurious in the spectrum
SINAD (Signal-to-Noise And Distortion): combination of SNR and THDSINAD = 20 * log ([Fundamental] / SQRT (SUM (SQR([Noise + Harmonics]))))
ENOB (Effective Number of Bits): (SINAD – 1.76) / 6.02
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More Information
http://www.maxim-ic.com/appnotes.cfm/appnote_number/641
http://inst.eecs.berkeley.edu/~ee247/fa05/lectures/L12_2_f05.pdf
http://inst.eecs.berkeley.edu/~ee247/fa05/lectures/L11b_f05.pdf
Preliminary
Slightly Advanced