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)

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 ???

Ideal DAC/ADC characteristics

DAC ADC

Integral Non-Linearity Error

INL: Deviation of the code transition from its ideal location

Differential Non-Linearity Error

DNL: Deviation of the code width from 1 LSB

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

Gain Error

Gain error: Difference between the slope of an actual transfer function matches the slope of the ideal transfer function

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

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