Datasheet

AD9125
Rev. 0 | Page 16 of 56
TERMINOLOGY
Integral Nonlinearity (INL)
INL 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.
Offset Error
The deviation of the output current from the ideal of zero is
called offset error. For IOUT1P, 0 mA output is expected when
the inputs are all 0s. For IOUT1N, 0 mA output is expected
when all 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 outputs
when all inputs are set to 1 vs. 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.
Tem p er atu re D r i ft
Temperature drift is specified as the maximum change from
the ambient (25°C) value to the value at either T
MIN
or T
MAX
.
For 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 (PSR)
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.
Spurious-Free Dynamic Range (SFDR)
The difference in decibels between the peak amplitude of the
output signal and the peak spurious signal within the dc to the
Nyquist frequency of the DAC. Typically, 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.
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
DATA
(interpolation rate), a digital filter can be constructed that
has a sharp transition band near f
DATA
/2. Images that typically
appear around f
DAC
(output data rate) can be greatly suppressed.
Adjacent Channel Leakage Ratio (ACLR)
The ratio in decibels relative to the carrier (dBc) between the
measured power within a channel and that of 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.
CLOCK GENERATOR
AND DISTRIBUTOR
DCI
DACCLK
DATA
32
I DAC
16
16
2
22
Q DAC
16
16
2
22
SIN
COS
NCO
FIFO
f
INTERFACE
f
DATA
/ f
HB1
f
NCO
/ f
HB2
f
HB3
f
DAC
WRITE
POINTER
READ
POINTER
LATCH
INPUT
DATA
FORMAT
09016-136
Figure 36. Defining Data Rates