Manual

MAX5886
3.3V, 12-Bit, 500Msps High Dynamic
Performance DAC with Differential LVDS Inputs
12 ______________________________________________________________________________________
If a single-ended unipolar output is desirable, IOUTP
should be selected as the output, with IOUTN ground-
ed. However, driving the MAX5886 single ended is not
recommended since additional noise is added (from
the ground plane) in such configurations.
The distortion performance of the DAC depends on the
load impedance. The MAX5886 is optimized for a 50Ω
double termination. It can be used with a transformer
output as shown in Figure 7 or just one 50Ω resistor
from each output to ground and one 50Ω resistor
between the outputs. This produces a full-scale output
power of up to 0dBm depending on the output current
setting. Higher termination impedance can be used at
the cost of degraded distortion performance and
increased output noise voltage.
Adjacent Channel Leakage Power Ratio
(ACLR) Testing for CDMA- and
W-CDMA-Based Base Station
Transceiver Systems (BTS)
The transmitter sections of BTS applications serving
CDMA and W-CDMA architectures must generate carri-
ers with minimal coupling of carrier energy into the
adjacent channels. Similar to the GSM/EDGE model
(see the Multitone Testing for GSM/EDGE Applications
section), a transmit mask (Tx mask) exists for this appli-
cation. The spread-spectrum modulation function
applied to the carrier frequency generates a spectral
response, which is uniform over a given bandwidth (up
to 4MHz) for a W-CDMA-modulated carrier.
A dominant specification is ACLR, a parameter which
reflects the ratio of the power in the desired carrier
band to the power in an adjacent carrier band. The
specification covers the first two adjacent bands, and is
measured on both sides of the desired carrier.
According to the transmit mask for CDMA and W-CDMA
architectures, the power ratio of the integrated carrier
channel energy to the integrated adjacent channel
energy must be >45dB for the first adjacent carrier slot
(ACLR 1) and >50dB for the second adjacent carrier
slot (ACLR 2). This specification applies to the output of
the entire transmitter signal chain. The requirement for
only the DAC block of the transmitter must be tighter,
with a typical margin of >15dB, requiring the DAC’s
ACLR 1 to be better than 60dB. Adjacent channel leak-
age is caused by a single spread-spectrum carrier,
which generates intermodulation (IM) products
MAX5886
T2, 1:1
T1, 1:1
V
OUT
, SINGLE ENDED
WIDEBAND RF TRANSFORMER T2
PERFORMS THE DIFFERENTIAL TO
SINGLE-ENDED CONVERSION.
50Ω
100Ω
50Ω
IOUTP
IOUTN
B0–B11
12
AV
DD
DV
DD
VCLK
AGND DGND CLKGND
Figure 7. Differential to Single-Ended Conversion Using a Wideband RF Transformer
MAX5886
50Ω
100Ω
50Ω
IOUTP
IOUTN
B0–B11
12
AV
DD
DV
DD
VCLK
AGND DGND CLKGND
OUTP
OUTN
Figure 8. MAX5886 Differential Output Configuration