AD4022BCPZ-R2 datasheet(17/39 Pages) AD

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Data Sheet

AD4020/AD4021/AD4022

Rev. B | Page 17 of 39

TERMINOLOGY

Integral Nonlinearity Error (INL)

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

from negative full scale through positive full scale. The point

used as negative full scale occurs ½ LSB before the first code

transition. Positive full scale is defined as a level 1½ LSB beyond

the last code transition. The deviation is measured from the

middle of each code to the true straight line (see Figure 39).

Differential Nonlinearity Error (DNL)

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

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

terms of resolution for which no missing codes are guaranteed.

Zero Error

Zero error is the difference between the ideal voltage that

results in the first code transition (½ LSB above analog ground)

and the actual voltage producing that code.

Gain Error

The first transition (from 100 … 00 to 100 … 01) occurs at a

level ½ LSB above nominal negative full scale (−4.999995 V for

the ±5 V range). The last transition (from 011 … 10 to 011 …

11) occurs for an analog voltage 1½ LSB below the nominal full

scale (+4.999986 V for the ±5 V range). The gain error is the

deviation of the difference between the actual level of the last

transition and the actual level of the first transition from the

difference between the ideal levels.

Spurious-Free Dynamic Range (SFDR)

SFDR is the difference, in decibels (dB), between the rms

amplitude of the input signal and the peak spurious signal.

Effective Number of Bits (ENOB)

ENOB is a measurement of the resolution with a sine wave

input. It is related to SINAD as follows:

ENOB = (SINAD − 1.76)/6.02

ENOB is expressed in bits and SINAD is expressed in dB..

Total Harmonic Distortion (THD)

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

expressed in decibels.

Dynamic Range

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

the total rms noise measured. The value for dynamic range is

expressed in decibels. It is measured with a signal at −60 dBFS

so that it includes 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 decibels.

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

SINAD is the ratio of the rms value of the actual input signal 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.

Aperture Delay

Aperture delay is the measure of the acquisition performance

and is the time between the rising edge of the CNV input and

when the input signal is held for a conversion.

Transient Response

Transient response is the time required for the ADC to acquire

a full-scale input step to ±1 LSB accuracy.

Common-Mode Rejection Ratio (CMRR)

CMRR is the ratio of the power in the ADC output at the

frequency, f, to the power of a 200 mV p-p sine wave applied to

the common-mode voltage of IN+ and IN− of frequency, f.

CMRR (dB) = 10log(PADC_IN/PADC_OUT)

where:

PADC_IN is the common-mode power at the frequency, f, applied

to the IN+ and IN− inputs.

PADC_OUT is the power at the frequency, f, in the ADC output.

Power Supply Rejection Ratio (PSRR)

PSRR is the ratio of the power in the ADC output at the

frequency, f, to the power of a 200 mV p-p sine wave applied to

the ADC VDD supply of frequency, f.

PSRR (dB) = 10 log(PVDD_IN/PADC_OUT)

where:

PVDD_IN is the power at the frequency, f, at the VDD pin.

PADC_OUT is the power at the frequency, f, in the ADC output.

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