max5888egktd Maxim Integrated Products, Inc., max5888egktd Datasheet - Page 12

• Manufacturer Part Number: max5888egktd
• Description: Max5888 3.3v, 16-bit, 500msps High Dynamic Performance Dac With Differential Lvds Inputs
• Manufacturer: Maxim Integrated Products, Inc.

amplitudes. It is also recommended to center tap the
transformer to ground. If no transformer is used, each
DAC output should be terminated to ground with a 50Ω
resistor. Additionally, a 100Ω resistor should be placed
between the outputs (Figure 8).
If a single-ended unipolar output is desirable, IOUTP
should be selected as the output, with IOUTN ground-
ed. However, driving the MAX5888 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 MAX5888 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.
3.3V, 16-Bit, 500Msps High Dynamic
Performance DAC with Differential LVDS Inputs
Figure 7. Differential to Single-Ended Conversion Using a Wideband RF Transformer
Figure 8. MAX5888 Differential Output Configuration
12
16
B0–B15
______________________________________________________________________________________
AGND
AV
DD
MAX5888
DGND
DV
DD
16
B0–B15
CLKGND
VCLK
AGND
AV
DD
IOUTN
IOUTP
MAX5888
DGND
DV
DD
50Ω
100Ω
50Ω
CLKGND
VCLK
OUTP
OUTN
IOUTN
IOUTP
50Ω
100Ω
50Ω
The transmitter sections of BTS applications serving
CDMA and WCDMA architectures must generate carri-
ers with minimal coupling of carrier energy into the adja-
cent channels. Similar to the GSM/EDGE model (see the
Multitone Testing for GSM/EDGE Applications section in
the Applications section), a transmit mask (Tx mask)
exists for this application. The spread-spectrum modula-
tion function applied to the carrier frequency generates a
spectral response, which is uniform over a given band-
width (up to 4MHz) for a WCDMA-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 WCDMA
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
between the frequency components located within the
carrier band. The energy at one end of the carrier band
generates IM products with the energy from the oppo-
site end of the carrier band. For single-carrier WCDMA
modulation, these IMD products are spread 3.84MHz
over the adjacent sideband. Four contiguous WCDMA
T1, 1:1
Adjacent Channel Leakage Power Ratio
T2, 1:1
PERFORMS THE DIFFERENTIAL TO
WIDEBAND RF TRANSFORMER T2
SINGLE-ENDED CONVERSION.
(ACLR) Testing for CDMA- and
WCDMA-Based Base Station
V
OUT
Transceiver Systems (BTS)
, SINGLE ENDED