AD7942 Analog Devices, AD7942 Datasheet - Page 12

• Manufacturer Part Number: AD7942
• Manufacturer: Analog Devices

Specifications of AD7942

• Resolution (bits): 14bit
• # Chan: 1
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

AD7942
TERMINOLOGY
Linearity Error or Integral Nonlinearity Error (INL)
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 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 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.
Offset Error
The first transition should occur at a level ½ LSB above analog
ground (152.6 μV for the 0 V to 5 V range). The offset error is
the deviation of the actual transition from that point.
Gain Error
The last transition (from 111...10 to 111...11) should occur
for an analog voltage 1½ LSB below the nominal full scale
(4.999542 V for the 0 V to 5 V range). The gain error is the
deviation of the actual level of the last transition from the
ideal level after the offset has been adjusted out.
Spurious-Free Dynamic Range (SFDR)
The difference, in decibels, 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 SINAD by the following formula and is
expressed in bits as follows:
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.
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 below the Nyquist
frequency, including harmonics but excluding dc. The value for
SINAD is expressed in decibels.
Aperture Delay
Aperture delay is a 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
The time required for the ADC to accurately acquire its input
after a full-scale step function was applied.
ENOB = (SINAD
dB
− 1.76)/6.02