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## AD7980 Datasheet(HTML) 8 Page - Analog Devices

 8 / 22 page AD7980Preliminary Technical DataRev Pr C | Page 8 of 22TERMINOLOGYIntegral 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.Offset ErrorThe first transition should occur at a level ½ LSB above analogground (38.1 μV for the 0 V to 5 V range). The offset error isthe deviation of the actual transition from that point.Gain ErrorThe last transition (from 111 . . . 10 to 111 . . . 11) should occurfor an analog voltage 1½ LSB below the nominal full scale(4.999886 V for the 0 V to 5 V range). The gain error is thedeviation of the actual level of the last transition from the ideallevel after the offset has been adjusted out.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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