AD9753-EB(Rev0) View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD9753-EB Datasheet PDF : 26 Pages
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40
35
30
25
20
15
10
5
0
0
2.5
5
7.5 10 12.5 15 17.5 20
IOUTFS – mA
Figure 17. IAVDD vs. IOUTFS
20
18
16
14
300MSPS
12
10
200MSPS
8
6
100MSPS
50MSPS
4
25MSPS
2
0
0.001
0.01
0.1
1
RATIO – fOUT/fDAC
Figure 18. IDVDD vs. fOUT/fDAC Ratio
10
DIV SETTING 11
9
8
7
DIV SETTING 10
DIV SETTING 01
6
5
4
DIV SETTING 00
3
2
1
0
0 25 50 75 100 125 150 175 200 225 250 275 300
fDAC – MHz
Figure 19. PLLVDD vs. fDAC
AD9753
APPLYING THE AD9753
OUTPUT CONFIGURATIONS
The following sections illustrate some typical output configura-
tions for the AD9753. Unless otherwise noted, it is assumed
that IOUTFS is set to a nominal 20 mA. For applications requir-
ing the optimum dynamic performance, a differential output
configuration is suggested. A differential output configuration
may consist of either an RF transformer or a differential op amp
configuration. The transformer configuration provides the opti-
mum high-frequency performance and is recommended for any
application allowing for ac-coupling. The differential op amp
configuration is suitable for applications requiring dc-coupling,
a 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 will
result if IOUTA and/or IOUTB are connected to an appropriately
sized load resistor, RLOAD, referred to ACOM. This configura-
tion may 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 since IOUTA or IOUTB is maintained
at a virtual ground. Note that IOUTA provides slightly better per-
formance than IOUTB.
DIFFERENTIAL COUPLING USING A TRANSFORMER
An RF transformer can be used to perform a differential-to-
single-ended signal conversion as shown in Figure 20. A
differentially coupled transformer output provides the optimum
distortion performance for output signals whose spectral content
lies within the transformer’s passband. An RF transformer such
as the Mini-Circuits T1–1T provides excellent rejection of com-
mon-mode distortion (i.e., even-order harmonics) and noise
over a wide frequency range. When IOUTA and IOUTB are termi-
nated to ground with 50 Ω, this configuration provides 0 dBm
power to a 50 Ω load on the secondary with a DAC full-scale
current of 20 mA. A 2:1 transformer such as the Coilcraft
WB2040-PC can also be used in a configuration in which IOUTA
and IOUTB are terminated to ground with 75 Ω. This configura-
tion improves load matching and increases power to 2 dBm into
a 50 Ω load on the secondary. Transformers with different imped-
ance ratios may also be used for impedance matching purposes.
Note that the transformer provides ac-coupling only.
AD9753
IOUTA
IOUTB
MINI-CIRCUITS
T1-1T
RLOAD
Figure 20. Differential Output Using a Transformer
REV. 0
–15–
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