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## AD7982 Datasheet(HTML) 13 Page - Analog Devices

 13 / 26 page AD7982Data SheetRev. D | Page 12 of 25TERMINOLOGYIntegral Nonlinearity Error (INL)INL refers to the deviation of each individual code from a linedrawn from negative full scale through positive full scale. Thepoint used as negative full scale occurs ½ LSB before the firstcode transition. Positive full scale is defined as a level 1½ LSBbeyond the last code transition. The deviation is measured fromthe middle of each code to the true straight line (see Figure 22).Differential Nonlinearity Error (DNL)In an ideal ADC, code transitions are 1 LSB apart. DNL is themaximum deviation from this ideal value. It is often specified interms of resolution for which no missing codes are guaranteed.Zero ErrorZero error is the difference between the ideal midscale voltage,that is, 0 V, from the actual voltage producing the midscaleoutput code, that is, 0 LSB.Gain ErrorThe first code transition (from 100 … 00 to 100 … 01) mustoccur at a level ½ LSB above nominal negative full scale(−4.999981 V for the ±5 V range). The last transition (from 011… 10 to 011 … 11) must occur for an analog voltage 1½ LSBbelow the nominal full scale (+4.999943 V for the ±5 V range).The gain error is the deviation of the difference between theactual level of the last transition and the actuallevel of the firsttransition from the difference between the ideal levels.Spurious-Free Dynamic Range (SFDR)SFDR is the difference, in decibels, between the rms amplitudeof the input signal and the peak spurious signal.Effective Number of Bits (ENOB)ENOB is a measurement of the resolution with a sine waveinput. It is related to SINAD as follows:ENOB = (SINADdB − 1.76)/6.02and is expressed in bits.Noise Free Code ResolutionNoise free code resolution is the number of bits beyond which it isimpossible to distinctly resolve individual codes. It is calculated asNoise Free Code Resolution = log2(2N/Peak-to-Peak Noise)and is expressed in bits.Effective ResolutionEffective resolution is calculated asEffective Resolution = log2(2N/RMS Input Noise)and is expressed in bits.Total Harmonic Distortion (THD)THD is the ratio of the rms sum of the first five harmoniccomponents to the rms value of a full-scale input signal and isexpressed in decibels.Dynamic RangeDynamic range is the ratio of the rms value of the full scale tothe total rms noise measured with the inputs shorted together.The value for dynamic range is expressed in decibels. It ismeasured with a signal at −60 dB so it includes all noise sourcesand DNL artifacts.Signal-to-Noise Ratio (SNR)SNR is the ratio of the rms value of the actual input signal to therms sum of all other spectral components below the Nyquistfrequency, excluding harmonics and dc. The value for SNR isexpressed in decibels.Signal-to-Noise-and-Distortion Ratio (SINAD)SINAD is the ratio of the rms value of the actual input signal tothe rms sum of all other spectral components that are less thanthe Nyquist frequency, including harmonics but excluding dc.The value of SINAD is expressed in decibels.Aperture DelayAperture delay is the measure of the acquisition performanceand is the time between the rising edge of the CNV input andwhen the input signal is held for a conversion.Transient ResponseTransient response is the time required for the ADC to accuratelyacquire its input after a full-scale step function is applied.