Datasheet AD7694 (Analog Devices) - 9

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AD7694 Data Sheet TERMINOLOGY Integral Nonlinearity Error (INL) Effective Number of Bits (ENOB)
Linearity error refers to the deviation of each individual code ENOB is a measurement of the resolution with a sine wave from a line drawn from negative full scale to positive full scale. input. It is related to S/(N + D) by The point used as negative full scale occurs ½ LSB before the ENOB = (S/[N + D]dB − 1.76)/6.02 first code transition. Positive full scale is defined as a level and is expressed in bits. 1 ½ LSB beyond the last code transition. The deviation is measured from the middle of each code to the true straight line
Total Harmonic Distortion (THD)
(see Figure 19). THD is the ratio of the rms sum of the first five harmonic components to the rms value of a full-scale input signal and is
Differential Nonlinearity Error (DNL)
expressed in dB. In an ideal ADC, code transitions are 1 LSB apart. DNL is the maximum deviation from this ideal value. It is often specified in
Signal-to-Noise Ratio (SNR)
terms of resolution for which no missing codes are guaranteed. SNR is the ratio of the rms value of the actual input signal to the rms sum of all other spectral components below the Nyquist
Offset Error
frequency, excluding harmonics and dc. The value for SNR is The first transition should occur at a level ½ LSB above analog expressed in dB. ground (38.1 µV for the 0 V to 5 V range). The offset error is the deviation of the actual transition from that point.
Signal-to-(Noise + Distortion) Ratio (S/[N + D])
S/(N+D) is the ratio of the rms value of the actual input signal
Gain Error
to the rms sum of all other spectral components below the The last transition (from 111.. 10 to 111.. 11) should occur for Nyquist frequency, including harmonics but excluding dc. The an analog voltage 1 ½ LSB below the nominal full scale value for S/(N+D) is expressed in dB. (4.999886 V for the 0 V to 5 V range). The gain error is the deviation of the actual level of the last transition from the ideal
Aperture Delay
level after the offset has been adjusted out. Aperture delay is a measure of the acquisition performance and the time between the rising edge of the CNV input and the time
Spurious-Free Dynamic Range (SFDR)
the input signal is held for conversion. The difference, in decibels (dB), between the rms amplitude of the input signal and the peak spurious signal.
Transient Response
The time required for the ADC to accurately acquire its input after a full-scale step function is applied. Rev. B | Page 8 of 16 Document Outline Features Applications General Description Application Diagram Table of Contents Revision History Specifications Timing Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Terminology Typical Performance Characteristics Application Information Circuit Information Converter Operation Transfer Functions Typical Connection Diagram Analog Input Driver Amplifier Choice Voltage Reference Input Power Supply Supplying the ADC from the Reference Digital Interface Layout Evaluating the AD7694 Performance Outline Dimensions Ordering Guide