AD9752 Analog Devices, AD9752 Datasheet - Page 13

• Manufacturer Part Number: AD9752
• Manufacturer: Analog Devices

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

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