AD7661 Analog Devices, AD7661 Datasheet - Page 11

• Manufacturer Part Number: AD7661
• Manufacturer: Analog Devices

Specifications of AD7661

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 100kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,2.5V p-p,Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

DEFINITIONS OF SPECIFICATIONS
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. 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.
Full-Scale Error
The last transition (from 011…10 to 011…11 in twos
complement coding) should occur for an analog voltage 1½ LSB
below the nominal full scale (2.49994278 V for the 0 V to 2.5 V
range). The full-scale error is the deviation of the actual level of
the last transition from the ideal level.
Unipolar Zero Error
The first transition should occur at a level ½ LSB above analog
ground (19.073 µV for the 0 V to 2.5 V range). Unipolar zero
error is the deviation of the actual transition from that point.
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.
Effective Number Of Bits (ENOB)
ENOB is a measurement of the resolution with a sine wave
input. It is related to S/(N+D) and is expressed in bits by the
following formula:
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 + 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 decibels.
ENOB = (S/[N+D]dB – 1.76)/6.02
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Aperture Delay
Aperture delay is a measure of the acquisition performance and
is measured from the falling edge of the CNVST input to when
the input signal is held for a conversion.
Transient Response
Transient response is the time required for the AD7661 to
achieve its rated accuracy after a full-scale step function is
applied to its input.
Overvoltage Recovery
Overvoltage recovery is the time required for the ADC to
recover to full accuracy after an analog input signal 150% of the
full-scale value is reduced to 50% of the full-scale value.
Reference Voltage Temperature Coefficient
Reference voltage temperature coefficient is derived from the
maximum and minimum reference output voltage (V
measured at T
using the following equation:
where:
V
V
V
T
T
Thermal Hysteresis
Thermal hysteresis is defined as the absolute maximum change
of reference output voltage after the device is cycled through
temperature from either
It is expressed in ppm using the following equation:
where:
V
V
MAX
MIN
REF
REF
REF
REF
REF
(Max) = Maximum V
(Min) = Minimum V
(25°C) = V
(25°C) = V
(T_HYS) = Maximum change of V
= –40°C
= +85°C
TCV
V
HYS
REF
(
ppm
(
MIN
T_HYS+ = +25°C to T
ppm
T_HYS– = +25°C to T
REF
REF
T_HYS–.
, T(25°C), and T
)
at +25°C
at 25°C
/
=
°
C
V
)
REF
=
REF
V
REF
(
REF
25
V
at T
at T
REF
°
(
V
C
25
MIN
REF
(
)
MIN
MAX
°
Max
−
C
, T(25°C), or T
(
, T(25°C), or T
V
)
25
. It is expressed in ppm/°C
MAX
MIN
×
REF
– )
°
REF
(
C
T
V
to +25°C
(
to +25°C
T
)
MAX
at T_HYS+ or
REF
_
(
HYS
–
Min
T
MIN
MAX
)
)
MAX
×
AD7661
)
REF
×
10
10
)
6
6