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## AD7982 Datasheet(HTML) 8 Page - Analog Devices

 8 / 23 pageAD7982Preliminary Technical DataRev PrC | Page 8 of 23TERMINOLOGYIntegral Nonlinearity Error (INL)It 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 (Figure 12).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 ErrorThe difference between the ideal midscale voltage, that is, 0 V,from the actual voltage producing the midscale output code,that is, 0 LSB.Gain ErrorThe first transition (from 100 . . . 00 to 100 . . . 01) should occurat a level ½ LSB above nominal negative full scale (−4.999981 Vfor the ±5 V range). The last transition (from 011…10 to011…11) should occur for an analog voltage 1½ LSB below thenominal full scale (+4.999943 V for the ±5 V range.) The gainerror is the deviation of the difference between the actual levelof the last transition and the actual level of the first transitionfrom the difference between the ideal levels.Spurious-Free Dynamic Range (SFDR)The difference, in decibels (dB), between the rms amplitude ofthe 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 S/(N+D) by the following formulaENOB = (S/[N + D]dB − 1.76)/6.02and is expressed in bits.Noise-free-code-resolutionIt is the number of bits beyond which it is impossible todistinctly resolve individual codes. It is calculated as :Noise-Free Code resolution = log2(2N/peak-to-peak noise)and is expressed in bits.Effective resolutionIt is calculated as :Effective 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 dB.Dynamic RangeIt is the ratio of the rms value of the full scale to the total rmsnoise measured with the inputs shorted together. The value fordynamic range is expressed in dB. It is measured with a signal at-60dBFs to include all noise sources and 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 dB.Signal-to-(Noise + Distortion) Ratio (S/[N+D])S/(N+D) is the ratio of the rms value of the actual input signalto the rms sum of all other spectral components below theNyquist frequency, including harmonics but excluding dc. Thevalue for S/(N+D) is expressed in dB.Aperture DelayThe measure of the acquisition performance and is the timebetween the rising edge of the CNV input and when the inputsignal is held for a conversion.Transient ResponseThe time required for the ADC to accurately acquire its inputafter a full-scale step function was applied.

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