AD9752 Analog Devices, AD9752 Datasheet - Page 13
AD9752
Manufacturer Part Number
AD9752
Description
Manufacturer
Analog Devices
Datasheet
1.AD9752.pdf
(23 pages)
Specifications of AD9752
Resolution (bits)
12bit
Dac Update Rate
125MSPS
Dac Settling Time
35ns
Max Pos Supply (v)
+5.5V
Single-supply
Yes
Dac Type
Current Out
Dac Input Format
Par
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SLEEP MODE OPERATION
The AD9752 has a power-down function which turns off the
output current and reduces the supply current to less than
8.5 mA over the specified supply range of 2.7 V to 5.5 V and
temperature range. This mode can be activated by applying a
logic level “1” to the SLEEP pin. This digital input also con-
tains an active pull-down circuit that ensures the AD9752 re-
mains enabled if this input is left disconnected. The AD9752
takes less than 50 ns to power down and approximately 5 s to
power back up.
POWER DISSIPATION
The power dissipation, P
several factors which include: (1) AVDD and DVDD, the
power supply voltages; (2) I
(3) f
input waveform. The power dissipation is directly proportional
to the analog supply current, I
rent, I
Figure 25 and is insensitive to f
Conversely, I
form, f
show I
(f
DVDD = 3 V, respectively. Note, how I
than a factor of 2 when DVDD is reduced from 5 V to 3 V.
REV. 0
OUT
CLOCK
/f
DVDD
DVDD
CLOCK
CLOCK
35
30
25
20
15
10
18
16
14
12
10
5
, the update rate; (4) and the reconstructed digital
8
6
4
2
0
Figure 26. I
0.01
. I
2
as a function of full-scale sine wave output ratios
) for various update rates with DVDD = 5 V and
, and digital supply DVDD. Figures 26 and 27
AVDD
DVDD
4
Figure 25. I
is directly proportional to I
is dependent on both the digital input wave-
6
DVDD
D
, of the AD9752 is dependent on
8
RATIO (f
OUTFS
vs. Ratio @ DVDD = 5 V
I
OUTFS
AVDD
10
CLOCK
AVDD
0.1
CLOCK
, the full-scale current output;
– mA
, and the digital supply cur-
12
vs. I
.
/f
OUT
DVDD
14
OUTFS
)
is reduced by more
16
OUTFS
125MSPS
100MSPS
50MSPS
25MSPS
5MSPS
18
as shown in
20
1
–13–
APPLYING THE AD9752
OUTPUT CONFIGURATIONS
The following sections illustrate some typical output configura-
tions for the AD9752. 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.
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 is connected to an appropri-
ately sized load resistor, R
figuration may be more suitable for a single-supply system
requiring a dc coupled, ground referred output voltage. Alterna-
tively, 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, IOUTA
provides slightly better performance 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 28. 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
common-mode distortion (i.e., 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. Trans-
formers with different impedance ratios may also be used for
impedance matching purposes. Note that the transformer
provides ac coupling only.
OUTFS
8
6
4
2
0
Figure 27. I
0.01
is set to a nominal 20 mA. For applications requir-
DVDD
LOAD
RATIO (f
vs. Ratio @ DVDD = 3 V
, referred to ACOM. This con-
0.1
CLOCK
/f
OUT
)
125MSPS
100MSPS
50MSPS
25MSPS
5MSPS
AD9752
1