Datasheet AD7683 (Analog Devices) - 9

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AD7683 Data Sheet TERMINOLOGY Integral Nonlinearity Error (INL)
Signal-to-(Noise + Distortion) Ratio (SINAD) Linearity error refers to the deviation of each individual code SINAD is the ratio of the rms value of the actual input signal to from a line drawn from negative full scale through positive the rms sum of all other spectral components below the Nyquist full scale. The point used as negative full scale occurs ½ LSB frequency, including harmonics but excluding dc. The value for before the first code transition. Positive full scale is defined as SINAD is expressed in dB. a level 1½ LSB beyond the last code transition. The deviation Effective Number of Bits (ENOB) is measured from the middle of each code to the true straight ENOB is a measurement of the resolution with a sine wave line (see Figure 22). input. It is related to SINAD (as represented by S/(N+D)) by Differential Nonlinearity Error (DNL) the following formula and is expressed in bits: In an ideal ADC, code transitions are 1 LSB apart. DNL is the ENOB = (S [ / N + D] − dB 1.76)/ 6.02 maximum deviation from this ideal value. It is often specified in terms of resolution for which no missing codes are guaranteed. Total Harmonic Distortion (THD) THD is the ratio of the rms sum of the first five harmonic Offset Error components to the rms value of a full-scale input signal and 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 Ratio (SNR) SNR is the ratio of the rms value of the actual input signal to Gain Error the rms sum of all other spectral components below the Nyquist The last transition (from 111.. 10 to 111.. 11) should occur for frequency, excluding harmonics and dc. The value for SNR is an analog voltage 1½ LSB below the nominal full scale 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 is the time between the falling edge of the CS input and when Spurious-Free Dynamic Range (SFDR) the input signal is held for a conversion. The difference, in decibels (dB), between the rms amplitude of the input signal and the peak spurious signal. Transient Response Transient response is 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 Application Diagram General Description Table of Contents Revision History Specifications Timing Specifications Timing and Circuit Diagrams Absolute Maximum Ratings Thermal Resistance ESD Caution Pin Configurations and Function Descriptions Terminology Typical Performance Characteristics Applications Information Circuit Information Converter Operation Transfer Functions Typical Connection Diagram Analog Input Driver Amplifier Choice Voltage Reference Input Power Supply Digital Interface Layout Evaluating the AD7683 Performance Outline Dimensions Ordering Guide