AD7663
DEFINITION OF SPECIFICATIONS
Effective Number of Bits (ENOB)
Integral Nonlinearity Error (INL)
A measurement of the resolution with a sine wave input. It is
related to S/(N+D) by the following formula:
Linearity error 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 1/2 LSB
before the first code transition. Positive full scale is defined as a
level 1 1/2 LSB beyond the last code transition. The deviation is
measured from the middle of each code to the true straight line.
ENOB = S N + D - 1.76 6.02
)
[
]
(
)
dB
and is expressed in bits.
Total Harmonic Distortion (THD)
The ratio of the rms sum of the first five harmonic components to
the rms value of a full-scale input signal, expressed in decibels.
Differential Nonlinearity Error (DNL)
In an ideal ADC, code transitions are 1 LSB apart. Differential
nonlinearity is the maximum deviation from this ideal value. It is
often specified in terms of resolution for which no missing codes
are guaranteed.
Signal-to-Noise Ratio (SNR)
The ratio of the rms value of the actual input signal to the rms
sum of all other spectral components below the Nyquist fre-
quency, excluding harmonics and dc. The value for SNR is
expressed in decibels.
Full-Scale Error
The last transition (from 011 . . . 10 to 011 . . . 11 in twos
complement coding) should occur for an analog voltage 1 1/2 LSB
below the nominal full scale (2.499886 V for the 2.5 V range).
The full-scale error is the deviation of the actual level of the last
transition from the ideal level.
Signal-to-(Noise + Distortion) Ratio (S/[N+D])
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 decibels.
Bipolar Zero Error
The difference between the ideal midscale input voltage (0 V) and
the actual voltage producing the midscale output code.
Aperture Delay
A measure of the acquisition performance measured from the
falling edge of the CNVST input to when the input signal is
held for a conversion.
Unipolar Zero Error
In Unipolar Mode, the first transition should occur at a level
1/2 LSB above analog ground. The unipolar zero error is the
deviation of the actual transition from that point.
Transient Response
The time required for the AD7663 to achieve its rated accuracy
after a full-scale step function is applied to its input.
Spurious-Free Dynamic Range (SFDR)
The difference, in decibels (dB), between the rms amplitude of
the input signal and the peak spurious signal.
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REV. B
ADI [ ADI ]
