AD7621 Analog Devices, AD7621 Datasheet - Page 11

• Manufacturer Part Number: AD7621
• Description: 16-Bit, 2 LSB INL, 3 MSPS PulSAR® ADC
• Manufacturer: Analog Devices

Specifications of AD7621

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 3MSPS
• Interface: Byte,Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

TERMINOLOGY
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 LSBs 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. 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.
Gain Error
The first transition (from 000…00 to 000…01) should occur for
an analog voltage ½ LSB above the nominal negative full-scale
(−2.0479688 V for the ±2.048 V range). The last transition
(from 111…10 to 111…11) should occur for an analog voltage
1½ LSBs below the nominal full-scale (2.0479531 V for the
±2.048 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.
Zero Error
The zero error is the difference between the ideal midscale
input voltage (0 V) and the actual voltage producing the
midscale output code.
Dynamic Range
Dynamic range is the ratio of the rms value of the full-scale to
the rms noise measured with the inputs shorted together. The
value for dynamic range 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.
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.
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Signal-to-(Noise + 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.
Spurious-Free Dynamic Range (SFDR)
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 and is expressed in bits by
Aperture Delay
Aperture delay is 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.
Transient Response
The time required for the AD7621 to achieve its rated accuracy
after a full-scale step function is applied to its input.
Reference Voltage Temperature Coefficient
Reference voltage temperature coefficient is derived from the
typical shift of output voltage at 25°C on a sample of parts at the
maximum and minimum reference output voltage (V
measured at T
where:
V
V
V
T
T
MAX
MIN
REF
REF
REF
(Max) = maximum V
(Min) = minimum V
(25°C) = V
ENOB = [(SINAD
= –40°C
TCV
= +85°C
REF
(
ppm/
MIN
REF
, T(25°C), and T
°
C
at 25°C
)
=
dB
V
REF
− 1.76)/6.02]
V
REF
REF
REF
(
25
at T
at T
(
Max
°
C
MAX
)
MIN
MIN
×
– )
, T (25°C), or T
T (
. It is expressed in ppm/°C as
, T (25°C), or T
V
MAX
REF
(
–
Min
T
MIN
)
)
×
10
MAX
MAX
6
AD7621
REF
)