AD9751 Analog Devices, AD9751 Datasheet - Page 16

• Manufacturer Part Number: AD9751
• Manufacturer: Analog Devices

Specifications of AD9751

• Resolution (bits): 10bit
• Dac Update Rate: 300MSPS
• Dac Settling Time: 11ns
• Max Pos Supply (v): +3.6V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

AD9751
10
40
35
30
25
20
15
10
20
18
16
14
12
10
0.001
9
8
7
6
5
4
3
2
1
0
5
0
8
6
4
2
0
0
0
DIV SETTING 11
25
Figure 18. I
2.5
50
Figure 19. PLLVDD vs. f
Figure 17. I
75
5
0.01
100
DIV SETTING 10
DVDD
7.5
RATIO (f
125
I
OUTFS
f
DAC
AVDD
vs. f
150
100MSPS
300MSPS
200MSPS
10
50MSPS
25MSPS
OUT
(MHz)
(mA)
/f
vs. I
OUT
175
DAC
12.5
DIV SETTING 01
/f
)
200
0.1
OUTFS
DAC
DIV SETTING 00
DAC
225
15
Ratio
250
17.5
275
300
20
1
–16–
APPLYING THE AD9751
OUTPUT CONFIGURATIONS
The following sections illustrate some typical output configura-
tions for the AD9751. Unless otherwise noted, it is assumed
that I
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 band-
width 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 I
sized load resistor, R
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
I
provides the best dc linearity, since I
at a virtual ground. Note that I
formance than I
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 pass band. An RF transformer such
as the Mini-Circuits T1–1T provides excellent rejection of
common-mode distortion (i.e., even-order harmonics) and
noise over a wide frequency range. When I
terminated 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 I
and I
tion improves load matching and increases power to 2 dBm into
a 50 Ω load on the secondary. Transformers with different
impedance ratios may also be used for impedance matching
purposes. Note that the transformer provides ac coupling only.
OUTA
Figure 20. Differential Output Using a Transformer
OUTB
OUTFS
or I
OUTA
OUTB
are terminated to ground with 75 Ω. This configura-
is set to a nominal 20 mA. For applications requir-
AD9751
and/or I
into a negative unipolar voltage. This configuration
OUTB
I
I
OUTA
OUTB
LOAD
.
OUTB
, referred to ACOM. This configura-
is connected to an appropriately
OUTA
MINI-CIRCUITS
provides slightly better per-
OUTA
T1-1T
or I
OUTA
OUTB
and I
R
is maintained
LOAD
OUTB
REV. C
are
OUTA