Datasheet AD7693 (Analog Devices) - 9

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AD7693 Data Sheet TERMINOLOGY Least Significant Bit (LSB) Transient Response
The LSB is the smallest increment that can be represented by a Transient response is the time required for the ADC to accurately converter. For a differential analog-to-digital converter with N acquire its input after a full-scale step function is applied. bits of resolution, the LSB expressed in volts is
Dynamic Range
Dynamic range is the ratio of the rms value of the full scale to V 2 REF LSB (V) = the total rms noise measured with the inputs shorted together. N 2 The value for dynamic range is expressed in decibels.
Integral Nonlinearity Error (INL) Signal-to-Noise Ratio (SNR)
INL refers to the deviation of each individual code from a line SNR is the ratio of the rms value of the actual input signal to the drawn from negative full scale through positive full scale. The rms sum of all other spectral components below the Nyquist point used as negative full scale occurs ½ LSB before the first frequency, excluding harmonics and dc. The value for SNR is code transition. Positive full scale is defined as a level 1½ LSB expressed in decibels. beyond the last code transition. The deviation is measured from the middle of each code to the true straight line (see Figure 26).
Signal-to-(Noise + Distortion) Ratio (SINAD)
SINAD is the ratio of the rms value of the actual input signal to
Differential Nonlinearity Error (DNL)
the rms sum of all other spectral components below the Nyquist In an ideal ADC, code transitions are 1 LSB apart. DNL is the frequency, including harmonics but excluding dc. The value for maximum deviation from this ideal value. It is often specified in SINAD is expressed in decibels. terms of resolution for which no missing codes are guaranteed.
Total Harmonic Distortion (THD) Zero Error
THD is the ratio of the rms sum of the first five harmonic Zero error is the difference between the ideal midscale voltage, components to the rms value of a full-scale input signal and is that is, 0 V, from the actual voltage producing the midscale expressed in decibels. output code, that is, 0 LSB.
Spurious-Free Dynamic Range (SFDR) Gain Error
SFDR is the difference, in decibels, between the rms amplitude The first transition (from 100 .. 00 to 100 .. 01) should occur at of the input signal and the peak spurious signal. a level ½ LSB above nominal negative full scale (−4.999847 V for the ±5 V range). The last transition (from 011 … 10 to
Effective Number of Bits (ENOB)
011 … 11) should occur for an analog voltage 1½ LSB below the ENOB is a measurement of the resolution with a sine wave nominal full scale (+4.999771 V for the ±5 V range.) The gain input. It is related to SINAD by the following formula: error is the deviation of the difference between the actual level ENOB = (SINADdB − 1.76)/6.02 of the last transition and the actual level of the first transition and is expressed in bits. from the difference between the ideal levels.
Aperture Delay
Aperture delay is the measure of the acquisition performance. It is the time between the rising edge of the CNV input and when the input signal is held for a conversion. Rev. B | Page 8 of 24 Document Outline Features Applications Application Diagram General Description Table of Contents Revision History Specification Timing Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Terminology Typical Performance Characteristics Theory of Operation Circuit Information Converter Operation Transfer Functions Typical Connection Diagram Analog Inputs Driver Amplifier Choice Single-Ended-to-Differential Driver Voltage Reference Input Power Supply Supplying the ADC from the Reference Digital Interface /CS Mode, 3-Wire Without Busy Indicator /CS Mode, 3-Wire with Busy Indicator /CS Mode, 4-Wire Without Busy Indicator /CS Mode, 4-Wire with Busy Indicator Chain Mode Without Busy Indicator Chain Mode with Busy Indicator Application Hints Layout Evaluating the AD7693 Performance Outline Dimensions Ordering Guide