9
FN6018.1
February 2002
Definition of Specifications
Crosstalk, is the measure of the channel isolation from one
DAC to the other. It is measured by generating a sinewave in
one DAC while the other DAC is clocked with a static input,
and comparing the output power of each DAC at the
frequency generated.
Differential Linearity Error, DNL, is the measure of the
step size output deviation from code to code. Ideally the step
size should be one LSB. A DNL specification of one LSB or
less guarantees monotonicity.
EDGE, Enhanced Data for Global Evolution, a TDMA
standard for cellular applications which uses 200kHz BW,
8-PSK modulated carriers.
Full Scale Gain Drift, is measured by setting the data inputs
to be all logic high (all 1s) and measuring the output voltage
through a known resistance as the temperature is varied
from T
MIN
to T
MAX
. It is defined as the maximum deviation
from the value measured at room temperature to the value
measured at either T
MIN
or T
MAX
. The units are ppm of FSR
(full scale range) per °C.
Full Scale Gain Error, is the error from an ideal ratio of 32
between the output current and the full scale adjust current
(through R
SET
).
Gain Matching, is a measure of the full scale amplitude
match between the I and Q channels given the same input
pattern. It is typically measured with all 1s at the input to both
channels, and the full scale output voltage developed into
matching loads is compared for the I and Q outputs.
Integral Linearity Error, INL, is the measure of the worst
case point that deviates from a best fit straight line of data
values along the transfer curve.
Internal Reference Voltage Drift, is defined as the
maximum deviation from the value measured at room
temperature to the value measured at either T
MIN
or T
MAX
.
The units are ppm per °C.
Offset Drift, is measured by setting the data inputs to all
logic low (all 0s) and measuring the output voltage at IOUTA
through a known resistance as the temperature is varied
from T
MIN
to T
MAX
. It is defined as the maximum deviation
from the value measured at room temperature to the value
measured at either T
MIN
or T
MAX
. The units are ppm of FSR
(full scale range) per degree °C.
Offset Error, is measured by setting the data inputs to all
logic low (all 0s) and measuring the output voltage of IOUTA
through a known resistance. Offset error is defined as the
maximum deviation of the IOUTA output current from a value
of 0mA.
Output Voltage Compliance Range, is the voltage limit
imposed on the output. The output impedance should be
chosen such that the voltage developed does not violate the
compliance range.
Power Supply Rejection, is measured using a single power
supply. The nominal supply voltage is varied
10% and the
change in the DAC full scale output is noted.
Reference Input Multiplying Bandwidth, is defined as the
3dB bandwidth of the voltage reference input. It is measured
by using a sinusoidal waveform as the external reference
with the digital inputs set to all 1s. The frequency is
increased until the amplitude of the output waveform is
0.707 (-3dB) of its original value.
Spurious Free Dynamic Range, SFDR, is the amplitude
difference from the fundamental signal to the largest
harmonically or non-harmonically related spur within the
specified frequency window.
Total Harmonic Distortion, THD, is the ratio of the RMS
value of the fundamental output signal to the RMS sum of
the first five harmonic components.
Detailed Description
The ISL5629 is a dual 8-bit, current out, CMOS, digital to
analog converter. The maximum update rate is at least
210+MSPS and can be powered by a single power supply in
the recommended range of +3.0V to +3.6V. Operation with
clock rates higher than 210MSPS is possible; please contact
the factory for more information. It consumes less than
125mW of power per channel when using a +3.3V supply,
the maximum 20mA of output current, and the data switching
at 210MSPS. The architecture is based on a segmented
current source arrangement that reduces glitch by reducing
the amount of current switching at any one time. In previous
architectures that contained all binary weighted current
sources or a binary weighted resistor ladder, the converter
might have a substantially larger amount of current turning
on and off at certain, worst-case transition points such as
midscale and quarter scale transitions. By greatly reducing
the amount of current switching at these major transitions,
the overall glitch of the converter is dramatically reduced,
improving settling time, transient problems, and accuracy.
Digital Inputs and Termination
The ISL5629 digital inputs are formatted as offset binary and
guaranteed to 3V LVCMOS levels. The internal register is
updated on the rising edge of the clock. To minimize
reflections, proper termination should be implemented. If the
lines driving the clock and the digital inputs are long 50
lines, then 50 termination resistors should be placed as
close to the converter inputs as possible connected to the
digital ground plane (if separate grounds are used). These
termination resistors are not likely needed as long as the
digital waveform source is within a few inches of the DAC.
For pattern drivers with very high speed edge rates, it is
recommended that the user consider series termination (50-
ISL5629
