EVAL-AD7482CB Analog Devices Inc, EVAL-AD7482CB Datasheet - Page 11

• Manufacturer Part Number: EVAL-AD7482CB
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD7482CB

• Lead Free Status / Rohs Status: Not Compliant

TERMINOLOGY
Integral Nonlinearity
The integral nonlinearity is the maximum deviation from a
straight line passing through the endpoints of the ADC transfer
function. The endpoints of the transfer function are zero scale, a
point 1/2 LSB below the first code transition, and full scale, a
point 1/2 LSB above the last code transition.
Differential Nonlinearity
The differential nonlinearity is the difference between the
measured and ideal 1 LSB change between any two adjacent
codes in the ADC.
Offset Error
The offset error is the deviation of the first code transition
(00...000) to (00...001) from the ideal, that is, AGND + 0.5 LSB.
Gain Error
The gain error is the deviation of the last code transition
(111...110) to (111...111) from the ideal, that is, V
after the offset error is adjusted out.
Track-and-Hold Acquisition Time
Track-and-hold acquisition time is the time required for the
output of the track-and-hold amplifier to reach its final value,
within ±1/2 LSB, after the end of conversion (the point at which
the track-and-hold returns to track mode).
Signal-to-Noise + Distortion (SINAD) Ratio
The SINAD ratio is the measured ratio of signal-to-noise +
distortion at the output of the ADC. The signal is the rms
amplitude of the fundamental. Noise is the sum of all nonfunda-
mental signals up to half the sampling frequency (f
dc. The ratio is dependent on the number of quantization levels
in the digitization process; the more levels, the smaller the
quantization noise. The theoretical SINAD ratio for an ideal N-bit
converter with a sine wave input is given by:
Therefore, this is 74 dB for a 12-bit converter.
Signal-to-Noise + Distortion = (6.02N +1.76)dB
S
/2), excluding
REF
− 1.5 LSB
Rev. A | Page 11 of 20
Total Harmonic Distortion (THD)
The THD is the ratio of the rms sum of the harmonics to the
fundamental. It is defined as
where V
V
sixth harmonics.
Peak Harmonic or Spurious Noise
The peak harmonic or spurious noise is the ratio of the rms
value of the next largest component in the ADC output spectrum
(up to f
The value of this specification is usually determined by the largest
harmonic in the spectrum, but for ADCs where the harmonics
are buried in the noise floor, it is a noise peak.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities creates distortion products
at sum and difference frequencies of mfa ± nfb, where m and n = 0,
1, 2, 3, and so on. Intermodulation distortion terms are those for
which neither m nor n is equal to zero. For example, the second
order terms include (fa + fb) and (fa − fb), whereas the third order
terms include (2fa + fb), (2fa − fb), (fa + 2fb), and (fa − 2fb).
The AD7482 is tested using the CCIF standard, where two input
frequencies near the top end of the input bandwidth are used. In
this case, the second order terms are usually distanced in frequency
from the original sine waves, whereas the third order terms are
usually at a frequency close to the input frequencies. As a result,
the second order and third order terms are specified separately.
The calculation of the intermodulation distortion is as per the
THD specification, where it is the ratio of the rms sum of the
individual distortion products to the rms amplitude of the sum
of the fundamentals expressed in dBs.
4
, V
THD
5
, and V
S
/2 and excluding dc) to the rms value of the fundamental.
1
is the rms amplitude of the fundamental and V
(
dB
6
)
are the rms amplitudes of the second through the
=
20
log
V
2
2
+
V
3
2
+
V
V
1
4
2
+
V
5
2
+
V
6
2
AD7482
2
, V
3
,