AD9739A Analog Devices, AD9739A Datasheet - Page 59

• Manufacturer Part Number: AD9739A
• Description: 14-Bit, 2.5 GSPS, RF D/A Converter
• Manufacturer: Analog Devices

Specifications of AD9739A

• Resolution (bits): 14bit
• Dac Update Rate: 2.5GSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): n/a
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: LVDS,Par

Data Sheet
OUTPUT STAGE CONFIGURATION
The
range applications that require wide signal reconstruction
bandwidth (that is, DOCSIS CMTS) and/or high IF/RF signal
generation. Optimum ac performance can be realized only if
the DAC output is configured for differential (that is, balanced)
operation with its output common-mode voltage biased to
analog ground. The output network used to interface to the
DAC should provide a near 0 Ω dc bias path to analog ground.
Any imbalance in the output impedance between the IOUTP
and IOUTN pins results in asymmetrical signal swings that
degrade the distortion performance (mostly even order) and noise
performance. Component selection and layout are critical in
realizing the performance potential of the AD9737A/AD9739A.
Most applications requiring balanced-to-unbalanced conversion
can take advantage of the Ruthroff 1:1 balun configuration
shown in Figure 181. This configuration provides excellent
amplitude/phase balance over a wide frequency range while
providing a 0 Ω dc bias path to each DAC output. Also, its design
provides exceptional bandwidth and can be considered for
applications requiring signal reconstruction of up to 2.2 GHz.
The characterization plots shown in this data sheet are based
on the
configuration. Figure 182 compares the measured frequency
response for normal and mix-mode using the
evaluation board vs. the ideal frequency response.
Figure 182. Measured vs. Ideal Frequency Response for Normal (Baseband)
Figure 181. Recommended Balun for Wideband Applications with Upper
AD9737A/AD9739A
and Mix-Mode Operation Using a TC1-33-75G Transformer on
–12
–15
–18
–21
–24
–27
–30
–33
–36
AD9737A/AD9739A
–3
–6
–9
0
0
IOUTN
IOUTP
BASEBAND
TC1-33-75G
70Ω
500
IDEAL MIX MODE
Bandwidths of up to 2.2 GHz
the
1000
90Ω
90Ω
AD9737A/AD9739A
IDEAL BASEBAND MODE
are intended to serve high dynamic
FREQUENCY (MHz)
1500
evaluation board, which uses this
2000
MINI-CIRCUITS
2500
EVB
TC1-33-75G+
TC1-33-75G
MIX MODE
AD9737A/AD9739A
3000
®
3500
Rev. | Page 59 of 64
C
Figure 183 shows an interface that can be considered when
interfacing the DAC output to a self-biased differential gain
block. The inductors shown serve as RF chokes (L) that provide
the dc bias path to analog ground. The value of the inductor, along
with the dc blocking capacitors (C), determines the lower cutoff
frequency of the composite pass-band response. An RF balun
should also be considered before the RF differential gain stage and
any filtering to ensure symmetrical common-mode impedance
seen by the DAC output while suppressing any common mode
noise, harmonics, and clock spurs prior to amplification.
For applications operating the
with output frequencies extending beyond 2.2 GHz, the circuits
shown in Figure 184 should be considered. The circuit in
Figure 184 uses a wideband balun with a configuration similar
to the one shown in Figure 183 to provide a dc bias path for the
DAC outputs. The circuit in Figure 185 takes advantage of ceramic
chip baluns to provide a dc bias path for the DAC outputs while
providing excellent amplitude/phase balance over a narrower
RF band. These low cost, low insertion loss baluns are available
for different popular RF bands and provide excellent amplitude/
phase balance over their specified frequency range.
Figure 184. Recommended Mix-Mode Configuration Offering Extended RF
Figure 183. Interfacing the DAC Output to the Self-Biased Differential
Figure 185. Lowest Cost and Size Configuration for Narrow RF Band
IOUTP
IOUTN
IOUTN
IOUTP
IOUTN
IOUTP
70Ω
70Ω
70Ω
Bandwidth Using a TC1-1-43A+ Balun
90Ω
90Ω
90Ω
90Ω
180Ω
L
L
Gain Stage
L
L
JOHANSON TECHNOLOGY
Operation
OPTIONAL BALUN AND FILTER
AD9737A/AD9739A
C
C
CHIP BALUNS
AD9737A/AD9739A
MURATA
MINI-CIRCUITS
TC1-1-462M
LPF
C
C
in mix-mode
RF DIFF
AMP