AD9244-EVAL Analog Devices, AD9244-EVAL Datasheet - Page 7

• Manufacturer Part Number: AD9244-EVAL
• Description: 14-Bit/ 40/65 MSPS Monolithic A/D Converter
• Manufacturer: Analog Devices

AD9244–SPECIFICATIONS
REV. PrD 01/22/02
DEFINITIONS OF SPECIFICATIONS
INTEGRAL NONLINEARITY (INL)
INL 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
1/2 LSB before the first code transition. “Positive full
scale” is defined as a level 1 1/2 LSB beyond the last code
transition. The deviation is measured from the middle of
each particular code to the true straight line.
DIFFERENTIAL NONLINEARITY (DNL, NO MISSING
CODES)
An ideal ADC exhibits code transitions that are exactly 1
LSB apart. DNL is the deviation from this ideal value.
Guaranteed no missing codes to 14-bit resolution indicates
that all 16384 codes, respectively, must be present over all
operating ranges.
ZERO ERROR
The major carry transition should occur for an analog
value 1/2 LSB below VIN+ = VIN-. Zero error is defined
as the deviation of the actual transition from that point.
GAIN ERROR
The first code transition should occur at an analog value
1/2 LSB above negative full scale. The last transition
should occur at an analog value 1 1/2 LSB below the
nominal full scale. Gain error is the deviation of the actual
difference between first and last code transitions and the
ideal difference between first and last code transitions.
TEMPERATURE DRIFT
The temperature drift for zero error and gain error speci-
fies the maximum change from the initial (+25°C) value
to the value at T
POWER SUPPLY REJECTION
The specification shows the maximum change in full scale
from the value with the supply at the minimum limit to the
value with the supply at its maximum limit.
APERTURE JITTER
The variation in aperture delay for successive samples
which is manifested as noise on the input to the A/D.
APERTURE DELAY
Aperture delay is a measure of the sample-and-hold ampli-
fier (SHA) performance and is measured from the rising
edge of the clock input to when the input signal is held for
conversion.
MIN
or T
MAX
.
PRELIMINARY TECHNICAL DATA
– 7 –
SIGNAL-TO-NOISE AND DISTORTION (S/N+D,
SINAD) RATIO
The ratio of the rms value of the measured 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.
EFFECTIVE NUMBER OF BITS (ENOB)
For a sine wave, SINAD can be expressed in terms of the
number of bits. Using the following formula,
it is possible to get a measure of performance expressed as
N, the effective number of bits.
Thus, effective number of bits for a device for sine wave
inputs at a given input frequency can be calculated directly
from its measured SINAD.
TOTAL HARMONIC DISTORTION (THD)
The ratio of the rms sum of the first six harmonic compo-
nents to the rms value of the measured input signal and is
expressed as a percentage or in decibels.
SIGNAL-TO-NOISE RATIO (SNR)
The ratio of the rms value of the measured input signal to
the rms sum of all other spectral components below the
Nyquist frequency, excluding the first six harmonics and
dc. The value for SNR is expressed in decibels.
SPURIOUS FREE DYNAMIC RANGE (SFDR)
The difference in dB between the rms amplitude of the
input signal and the peak spurious signal.
NYQUIST SAMPLING
When the frequency components of the analog input are
below the Nyquist frequency (Fclock/2), this is often re-
ferred to as Nyquist sampling.
IF SAMPLING
Due to the effects of aliasing, an ADC is not necessarily
limited to Nyquist sampling. Higher sampled frequencies
will be aliased down into the 1st Nyquist zone (DC-
Fclock/2) on the output of the ADC. Care must be taken
that the bandwidth of the sampled signal does not overlap
Nyquist zones and alias onto itself. Nyquist sampling per-
formance is limited by the bandwidth of the input SHA
and clock jitter (jitter adds more noise at higher input
frequencies).
N = (SINAD – 1.76)/6.02