Terminology - Analog Devices AD9776 Instruction Manual

AD9776/AD9778/AD9779

TERMINOLOGY

Linearity Error (Integral Nonlinearity or INL)
Linearity error is defined as the maximum deviation of the
actual analog output from the ideal output, determined by a
straight line drawn from zero scale to full scale.
Differential Nonlinearity (DNL)
DNL is the measure of the variation in analog value, normalized
to full scale, associated with a 1 LSB change in digital input
code.
Monotonicity
A DAC is monotonic if the output either increases or remains
constant as the digital input increases.
Offset Error
The deviation of the output current from the ideal of zero is
called offset error. For I , 0 mA output is expected when the
OUTA
inputs are all 0s. For I , 0 mA output is expected when all
OUTB
B
inputs are set to 1.
Gain Error
The difference between the actual and ideal output span. The
actual span is determined by the difference between the output
when all inputs are set to 1 and the output when all inputs are
set to 0.
Output Compliance Range
The range of allowable voltage at the output of a current-output
DAC. Operation beyond the maximum compliance limits can
cause either output stage saturation or breakdown, resulting in
nonlinear performance.
Temperature Drift
Temperature drift is specified as the maximum change from the
ambient (25°C) value to the value at either T
offset and gain drift, the drift is reported in ppm of full-scale
range (FSR) per degree Celsius. For reference drift, the drift is
reported in ppm per degree Celsius.
Power Supply Rejection
The maximum change in the full-scale output as the supplies
are varied from minimum to maximum specified voltages.
Settling Time
The time required for the output to reach and remain within a
specified error band around its final value, measured from the
start of the output transition.
or T . For
MIN MAX
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In-Band Spurious Free Dynamic Range (SFDR)
The difference, in decibels, between the peak amplitude of the
output signal and the peak spurious signal between dc and the
frequency equal to half the input data rate.
Out-of-Band Spurious Free Dynamic Range (SFDR)
The difference, in decibels, between the peak amplitude of the
output signal and the peak spurious signal within the band that
starts at the frequency of the input data rate and ends at the
Nyquist frequency of the DAC output sample rate. Normally,
energy in this band is rejected by the interpolation filters. This
specification therefore defines how well the interpolation filters
work and the effect of other parasitic coupling paths to the DAC
output.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of the first six harmonic com-
ponents to the rms value of the measured fundamental. It is
expressed as a percentage or in decibels.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the measured output 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.
Interpolation Filter
If the digital inputs to the DAC are sampled at a multiple rate of
f (interpolation rate), a digital filter can be constructed that
DATA
has a sharp transition band near f
appear around f (output data rate) can be greatly suppressed.
DAC
Adjacent Channel Leakage Ratio (ACLR)
The ratio in dBc between the measured power within a channel
relative to its adjacent channel.
Complex Image Rejection
In a traditional two-part upconversion, two images are created
around the second IF frequency. These images have the effect of
wasting transmitter power and system bandwidth. By placing
the real part of a second complex modulator in series with the
first complex modulator, either the upper or lower frequency
image near the second IF can be rejected.
/2. Images that typically
DATA