Datasheet AD7981-KGD (Analog Devices) - 8

AD7981-KGD Known Good Die TERMINOLOGY Integral Nonlinearity (INL) Effective Resolution
INL refers to the deviation of each individual code from a line Effective resolution is calculated as drawn from negative full scale through positive full scale. The Effective Resolution = log2(2N/RMS Input Noise) point used as negative full scale occurs ½ LSB before the first code transition. Positive full scale is defined as a level 1½ LSB and is expressed in bits. beyond the last code transition. The deviation is measured from
Total Harmonic Distortion (THD)
the middle of each code to the true straight line. THD is the ratio of the rms sum of the first five harmonic
Differential Nonlinearity (DNL)
components to the rms value of a full-scale input signal and is In an ideal ADC, code transitions are 1 LSB apart. DNL is the expressed in dB. maximum deviation from this ideal value. It is often specified in
Dynamic Range
terms of resolution for which no missing codes are guaranteed. Dynamic range is the ratio of the rms value of the ful scale to
Zero Error
the total rms noise measured with the inputs shorted together. It The first transition occurs at a level ½ LSB above analog ground is measured with a signal at −60 dBFS to include all noise (38.1 µV for the 0 V to 5 V range). The offset error is the sources and DNL artifacts. The value for dynamic range is deviation of the actual transition from that point. expressed in dB.
Gain Error Signal-to-Noise Ratio (SNR)
The last transition (from 111 … 10 to 111 … 11) occurs for an SNR is the ratio of the rms value of the actual input signal to the analog voltage 1½ LSB below the nominal full scale (4.999886 V rms sum of all other spectral components below the Nyquist for the 0 V to 5 V range). The gain error is the deviation of the frequency, excluding harmonics and dc. The value for SNR is actual level of the last transition from the ideal level after the expressed in dB. offset is adjusted out.
Signal-to-Noise-and-Distortion (SINAD) Ratio Spurious-Free Dynamic Range (SFDR)
SINAD is the ratio of the rms value of the actual input signal to SFDR is the difference, in decibels (dB), between the rms the rms sum of all other spectral components below the Nyquist amplitude of the input signal and the peak spurious signal. frequency, including harmonics but excluding dc. The value for SINAD is expressed in dB.
Effective Number of Bits (ENOB)
ENOB is a measurement of the resolution with a sine wave
Aperture Delay
input. It is related to SINAD by the following formula: Aperture delay is the measure of the acquisition performance. It is the time between the rising edge of the CNV input and when ENOB = (SINADdB − 1.76)/6.02 the input signal is held for a conversion. and is expressed in bits.
Transient Response Noise-Free Code Resolution
Transient response is the time required for the ADC to Noise-free code resolution is the number of bits beyond which accurately acquire its input after a full-scale step function is it is impossible to distinctly resolve individual codes. It is applied. calculated as Noise-Free Code Resolution = log2(2N/Peak-to-Peak Noise) and is expressed in bits. Rev. A | Page 8 of 9 Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TERMINOLOGY OUTLINE DIMENSIONS DIE SPECIFICATIONS AND ASSEMBLY RECOMMENDATIONS ORDERING GUIDE