AD4693 datasheet(20/77 Pages) AD

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Data Sheet

AD4693/AD4694

TERMINOLOGY

analog.com

Rev. 0 | 20 of 77

Integral Nonlinearity Error (INL)

INL is the deviation of each individual code from a line drawn

through the two endpoints of the ADC transfer function. The two

endpoints of the transfer function are ½ LSB before the first code

transition and 1½ LSB beyond the last code transition. The devia-

tion is measured from the middle of each code to the true straight

line.

Differential Nonlinearity Error (DNL)

In an ideal ADC, code transitions are 1 LSB apart. DNL is the

maximum deviation from this ideal value. DNL is often specified in

terms of resolution for which no missing codes are guaranteed.

Offset Error

The offset error is the deviation of the measured transition between

−FSR and −FSR + 1 from the ideal transition. The ideal transition

between −FSR and −FSR + 1 occurs at an analog input level

½ LSB above 0V (see the Transfer Function section).

Offset error drift is the typical change in offset error vs. temperature,

expressed in μV/°C. Offset error match is the largest difference in

offset error between any two input channels for a given device.

Gain Error

Gain error is the deviation of the slope of the measured transfer

function and the ideal transfer function. The ideal slope is VREF/216.

Gain error drift is the typical change in gain error vs. temperature,

expressed in ppm/°C. Gain error match is the largest difference in

gain error between any two input channels for a given device.

Full-Scale Error

The full-scale error is the deviation of the measured transition

between +FSR – 1 and +FSR from the ideal transition, measured

in LSBs. The ideal transition between +FSR − 1 and +FSR occurs

for an analog input level 1½ LSB below the nominal full scale (see

the Transfer Function section). Full-scale error is combination of the

offset and gain errors for each device.

Full-scale error drift is the typical change in full-scale error vs.

temperature, expressed in ppm/°C.

Dynamic Range

Dynamic range is the ratio of the RMS value of the full scale to

the total RMS noise measured with the inputs shorted together. The

value for dynamic range is expressed in dB and 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

the RMS sum of all other spectral components below the Nyquist

frequency, excluding harmonics and DC. The value for SNR is

expressed in dB.

Total Harmonic Distortion (THD)

THD is the ratio of the RMS sum of harmonics to the fundamental

and is defined as

THDdB =20log V22+V32+V42+V52+V62

(1)

where:

V1 is the RMS amplitude of the fundamental.

V2, V3, V4, V5, and V6 are the RMS amplitudes of the second

through the sixth harmonic.

Signal-to-Noise-and-Distortion Ratio (SINAD)

SINAD is the ratio of the RMS voltage of a full-scale sine wave to

the RMS sum of all other spectral components that are less than

the Nyquist frequency, including harmonics but excluding DC. The

value of SINAD is expressed in decibels.

Effective Number of Bits (ENOB)

ENOB is a measurement of the resolution with a sine wave input

and is related to SINAD by the following formula:

ENOB = (SINAD − 1.76)/6.02

ENOB is expressed in bits.

Spurious-Free Dynamic Range (SFDR)

SFDR is the difference, in decibels (dB), between the RMS ampli-

tude of the input signal and the peak spurious signal.

Channel-to-Channel Crosstalk

Channel-to-channel crosstalk is a measure of the level of crosstalk

from a signal on an inactive channel to an active channel. Channel-

to-channel crosstalk is measured by applying a full-scale interferer

sine wave on one or more channels and a DC mid-scale signal on

the active channel. The channel-to-channel crosstalk is the ratio of

the amplitude of the interferer sine wave and the amplitude of the

spectrum of the active channel at the same frequency.

Channel-to-Channel Memory

Channel-to-channel memory is a measure of the level of crosstalk

that occurs when switching between channels in a channel se-

quence. It is measured by applying a full-scale interferer sine wave

to one analog input channel and a DC voltage on another analog

input channel, and repeatedly alternating sampling between the

two channels on each conversion. The channel-to-channel memory

is the ratio of the amplitude of the interferer sine wave and the

amplitude of the spectrum of the DC-driven channel at the same

frequency.

Aperture Delay

Aperture delay is the measure of the acquisition performance.

Aperture delay is the time between the rising edge of the CNV

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