ADAQ23876BBCZ datasheet(23/37 Pages) AD

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Data Sheet

ADAQ23876

TERMINOLOGY

analog.com

Rev. 0 | 23 of 37

Integral Nonlinearity (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.

Differential Nonlinearity (DNL)

In an ideal µModule, 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.

Offset Error

The first transition occurs at a level ½ LSB above analog ground

(62.5 µV for the gain = 1.38, ±2.5 V range). Offset error is the

difference between the ideal midscale input voltage (0 V) and the

actual voltage producing the midscale output code.

Offset Error Drift

Drift offset error drift is the ratio of the offset error change due to

a temperature change of 1°C and the full-scale code range (gain =

1.38, ±2.5 V range). This drift is expressed in parts per million per

degree Celsius as follows:

Offset Error Drift (ppm/°C) = 106 × (Offset Error_TMAX − Offset

Error_TMIN)/ (TMAX − TMIN)

where: TMAX = 85°C and TMIN = −40°C.

Gain Error

The first transition (from 100…000 to 1000…001) occurs at a level

½ LSB above nominal negative full scale and the last transition

(from 011…110 to 011…111) occurs for an analog voltage 1½ LSB

below the nominal positive full scale. 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 ideal levels after the

offset error is removed. In addition, the absolute accuracy of the

reference used for the µModule can be a large source of error.

Therefore, this error source is removed by measuring its value and

using it to determine positive full scale (PFS) and negative full scale

(NFS) for the gain error calculation. If the reference used cannot be

measured, its deviation from ideal must be factored into the gain

error calculation.

This error is expressed in percentage as follows:

Gain_Error % =100× PFS−NFSACTUAL_CODE

− PFS−NFSIDEAL_CODE/PFS−NFSIDEAL_CODE

where:

PFS is positive full scale.

NFS is negative full scale.

Gain Error Drift

Gain error drift is the ratio of the gain error change due to a

temperature change of 1°C and the full-scale range (gain = 0.37,

±10 V range). This drift is expressed in parts per million per degree

Celsius as follows:

Gain Error Drift (ppm/°C) = 106 × (Gain Error_TMAX – Gain

Error_TMIN)/(TMAX − TMIN)

where: TMAX = 85°C and TMIN = −40°C.

Spurious-Free Dynamic Range (SFDR)

SFDR is defined as the difference, in dB, between the peak spuri-

ous or harmonic component in the ADC output spectrum (up to fS/2

and excluding dc) and the rms value of the fundamental.

Effective Number of Bits (ENOB)

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

ENOB is related to SINAD and expressed in bits as follows:

ENOB = (SINADdB − 1.76)/6.02

Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of the first five harmonic compo-

nents 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 (SINAD) Ratio

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 µModule to acquire

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

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