ad7688brm Analog Devices, Inc., ad7688brm Datasheet - Page 8

• Manufacturer Part Number: ad7688brm
• Description: 16-bit, 1.5 Lsb Inl, 500 Ksps Pulsar? Differential Adc In Msop/qfn
• Manufacturer: Analog Devices, Inc.

AD7688
TERMINOLOGY
Integral Nonlinearity Error (INL)
It refers to 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 (Figure 25).
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
It is the difference between the ideal midscale voltage, that is, 0
V, from the actual voltage producing the midscale output code,
that is, 0 LSB.
Gain Error
The first transition (from 100 . . . 00 to 100 . . . 01) should occur
at a level ½ LSB above nominal negative full scale (−4.999924 V
for the ±5 V range). The last transition (from 011…10 to
011…11) should occur for an analog voltage 1½ LSB below the
nominal full scale (+4.999771 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.
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Effective Number of Bits (ENOB)
ENOB is a measurement of the resolution with a sine wave
input. It is related to S/(N+D) by the following formula
and is expressed in bits.
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 dB.
Dynamic Range
It 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.
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.
Signal-to-(Noise + Distortion) Ratio (S/[N+D])
S/(N+D) 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, including harmonics but excluding dc. The
value for S/(N+D) is expressed in dB.
Aperture Delay
Aperature 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.
Transient Response
It is the time required for the ADC to accurately acquire its
input after a full-scale step function was applied.
ENOB = (S/[N + D]
dB
− 1.76)/6.02