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REV. B
AD7676
–7–
DEFINITION OF SPECIFICATIONS
Integral Nonlinearity Error (INL)
Integral nonlinearity is the maximum deviation of a straight line
drawn through the transfer function of the actual ADC. The
deviation is measured from the middle of each code.
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 comple-
ment 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.
–Full-Scale Error
The first transition (from 100 ... 00 to 100 . . . 01 in twos comple-
ment coding) should occur for an analog voltage 1/2 LSB above
the nominal –full scale (–2.499962 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.
Bipolar Zero Error
The bipolar zero error is the difference between the ideal midscale
input voltage (0 V) and the actual voltage producing the midscale
output code.
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 S/(N+D) by the following formula:
ENOB
S
N
D
dB
=+
[]
()
/– .
/ .
176
6 02
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 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 (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 decibels (dB).
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
The time required for the AD7676 to achieve its rated accuracy
after a full-scale step function is applied to its input.
PIN CONFIGURATION
36
35
34
33
32
31
30
29
28
27
26
25
13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
10
11
12
48 47 46 45 44
39 38 37
43 42 41 40
PIN 1
IDENTIFIER
TOP VIEW
(Not to Scale)
AGND
CNVST
PD
RESET
CS
RD
DGND
AGND
AVDD
NC
BYTESWAP
OB/
2C
NC
NC = NO CONNECT
SER/
PAR
D0
D1
D2/DIVSCLK[0]
BUSY
D15
D14
D13
AD7676
D3/DIVSCLK[1]
D12
NC
IN+
NC
IN–
REFGND
REF
D4/EXT/
INT
D5/INVSYNC
D6/INVSCLK
D7/RDC/SDIN
OGND
OV
D
DV
D
DGND
D8/SDOUT
D9/SCLK
D10/SYNC
D11/RDERR
OR