AD9740-EB View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD9740-EB Datasheet PDF : 32 Pages
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35
30
25
20
15
10
0
2
4
6
8 10 12 14 16 18 20
IOUTFS (mA)
Figure 29. IAVDD vs. IOUTFS
20
18
210MSPS
16
14
165MSPS
12
10
125MSPS
8
6
65MSPS
4
2
0
0.01
0.1
1
RATIO (fOUT/fCLOCK)
Figure 30. IDVDD vs. Ratio @ DVDD = 3.3 V
11
10
9
DIFF
8
7
6
PECL
5
SE
4
3
2
1
0
0
50
100
150
200
250
fCLOCK (MSPS)
Figure 31. ICLKVDD vs. fCLOCK and Clock Mode
AD9740
APPLYING THE AD9740
Output Configurations
The following sections illustrate some typical output
configurations for the AD9740. Unless otherwise noted, it is
assumed that IOUTFS is set to a nominal 20 mA. For applications
requiring the optimum dynamic performance, a differential
output configuration is suggested. A differential output
configuration can consist of either an RF transformer or a
differential op amp configuration. The transformer
configuration provides the optimum high frequency
performance and is recommended for any application that
allows ac coupling. The differential op amp configuration is
suitable for applications requiring dc coupling, bipolar output,
signal gain, and/or level shifting within the bandwidth of the
chosen op amp.
A single-ended output is suitable for applications requiring a
unipolar voltage output. A positive unipolar output voltage
results if IOUTA and/or IOUTB is connected to an
appropriately sized load resistor, RLOAD, referred to ACOM.
This configuration can be more suitable for a single-supply
system requiring a dc-coupled, ground referred output voltage.
Alternatively, an amplifier could be configured as an I-V
converter, thus converting IOUTA or IOUTB into a negative
unipolar voltage. This configuration provides the best dc linearity
because IOUTA or IOUTB is maintained at a virtual ground.
DIFFERENTIAL COUPLING USING A TRANSFORMER
An RF transformer can be used to perform a differential-to-
single-ended signal conversion, as shown in Figure 32. A
differentially coupled transformer output provides the
optimum distortion performance for output signals whose
spectral content lies within the transformer’s pass band. An
RF transformer, such as the Mini-Circuits® T1–1T, provides
excellent rejection of common-mode distortion (that is, even-
order harmonics) and noise over a wide frequency range. It also
provides electrical isolation and the ability to deliver twice the
power to the load. Transformers with different impedance ratios
can also be used for impedance matching purposes. Note that
the transformer provides ac coupling only.
IOUTA 22
MINI-CIRCUITS
T1-1T
AD9740
RLOAD
IOUTB 21
OPTIONAL RDIFF
Figure 32. Differential Output Using a Transformer
Rev. B | Page 17 of 32
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