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AD9713 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD9713
Beschreibung 100MSPS D/A CONVERTERS
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 8 Seiten
AD9713 Datasheet, Funktion
ANALOG DEVICES fAX-ON-DEHAND HOTLINE - Page 23
ANALOG
W DEVICES
12-Bit,100MSPS
UtAConverters
I AD97121AD9713I
FEATURES
100 MSPS Update Rate
ECL/TTL Compatibility
Low Glitch Impulse: 100 pV-s
Fast Settling: 30 ns to %1 LSB
Low Power: 700 mW
FUNCTIONAL BLOCK DIAGRAM
AD9712/AD9713
APPUCA TlONS
ATE
Signal Reconstruction
Arbitrary Waveform Generators
Digital Synthesizers
Signal Generators
OGENERAL DESCRIPTION
BThe AD9712 and AD9713 are I2-bit, high speed digital-
Sto-analog converters constructed in an advanced oxide isolated
bipolar process. The AD9712 is an ECL-compatible device
OfeatUring update rates of 100 MSPS minimum; the TTL-
compatible AD9713 will update at 80 MSPS minimum.
LDesigned for direct digital synthesis, waveform reconstruction,
Eand high resolution imaging applications, both devices feature
low glitch impulse of 100 pV-s; and fast settling times of 30 ns
TEto :!:1 LSB. Both units are characterized for dynamic perfor-
~2o)oo
REFERENCEY
OUT L
o(191
YcONTROL
I AMP IN
The AD9712 and AD9713 are available in 28-pin plastic DIPs
and PLCCs, with an operating temperature range of 0 to + 70°C.
Contact the factory for availability of military-grade devices.
c
~w
0a: .m.:
mance, and have excellent harmonic suppression.
C) %
~iii ;i
Q' a
Q'
Q
~
C
5
<>
~~
61 LATCH ENABLE
ANALOG RETURN 113
!I DIGITAL+V.
rn REFERENCE GROUND
:2J REFERENCE OUT
;1" CONTROL AMP IN
.!!.I CONTROL AMP OUT
m REFERENCE IN
51 ANALOG-V.
Plastic DIPPinout Designations (Top View)
221 REFERENCE GROUND
~ REFERENCE OUT
191 CONTROL AMP IN
I-,,:'
'9"
B~ w0%~,o., .:.:aE5.
:! ~ c:
~.. II!
0
0
PLCC Pinout Designations
REV.A
Information furnished by Analog Devices is believed to be accurate and
reliable. However. no responsibility is assumed by Analog Devices for its
use. nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way. P.O. Box 9106. Norwood. MA 02062-9106
Tel: 617/329-4700 Fax: 617/326-8703 Twx: 710/394-6577
We5t CQut
Central
Atlantic:
714/641-9391
214/231-5094
215/643.7790
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AD9713 Datasheet, Funktion
ANALOG DEVICES fAX-ON-DEMAND HOTLINE - Page 28
AD9712/AD9713
Outputs
The Switch Network controls complementary current outputs
lOUT and lOUT' As indicated earlier, DcD. are decoded into IS
"thermometer code" lines which drive matched current sources.
the DAC output as shown in Figure 5. Reducing DAC full-scale
outpUt current degrades both linearity and settling time; there-
fore, the current divider method is preferable.
Ds and D6 control weighted current sources; and D7-D12 are
applied to the R-2R network.
This segmentation reduces frequency domain errors due to'
glitch impulse. Current is steered to either lOUT or lOUT in pro-
portion to the digital input code. The sum of the two currents is
always equal to the full-scale output current minus one LSB.
The current output can be converted to a voltage by resistive
loading as shown in Figure 4. Both louT and lOUT should be
.V."'
R"
RL
v"'"
V'OLL 8C.ILE ~ .5V
Yu.a"" =-5V
loaded equally for best overall performance. The voltage which
RL
is developed is the product of the output current and the value
of the load resistor.
O.'"F*
-uv
OBSO -eeL
LDRIVE
ETELOGIC
Figure 5. IN Conversion Using Current Feedback Amp
The DAC output is not clamped at virtual ground in this config-
uration because of the series resistance RFF' The value of RFF is
selected according to the equation:
-RLIFS
V Full Seal<
R FB
+ I OFF
RL
RFF =
V Full Scale
R FB
+ I OFF
As an example, assume the following conditions:
RL 0=50 n
RFB = 1.5 kG
IFs = 20.48 mA
IOFF---VZerosC'.oIe- - 33. mA
RFB
Given these conditions, RFF = 103.6 fl
S'lSTI!M
CAOuICI
Figure 4. Typical Resistive Load Connection
When operating at the nominal full.scale current of 20.48 mA,
the voltage swing will be from 0 to -1.024 V across SOfl resis-
tors. Bipolar outputs are possible by sourcing a current equal to
half the DAC full-scale current into the load resistor.
An alternate method of converting the current oUtput to voltage
is by driving the summing node of an operational amplifier
directly with a feedback resistor selected according [0 "the
equation:
RFS = VOUT(FSI / lOUT (FS)
A current feedback amplifier such as the AD9610 offers signifi.
cantly faster settling and greater bandwidth than a conventional
voltage feedback op amp. The feedback resistor for the AD9610
must be 1.5 kfl or greater to maintain stability. This value for
RFB' along with the 20.48 mA full-scale output current, results
in a full-scale output of 30 V, which exceeds the output range of
the AD9610.
Full-scale output voltage can be reduced by either reducing the
DAC's full-scale output current, or by using a current divider at
Power and Grounding
Maintaining low noise on power supplies and ground is critical
for obtaining optimum results with the AD9712 or AD9713.
DACs are most often used in circuits which are predominantly
digitaL To preserve 12-bit performance, especially at conversion
speeds up to 100 MSPS, special precautions are necessary for
power supplies and grounding.
Ideally, the DAC should have a separate analog ground plane.
All ground pins of the DAC, as well as reference and analog
output components, should be tied directly to this analog
ground plane. The DAC's ground plane should be connected to
the system ground plane at a single point.
Ferrite beads, along with high frequency, low inductance decou-
piing capacitors, should be used for the supply connections ro
isolate digital switching currents from the DAC supply pins.
Separate isolation networks for the digital and analog supply
connections will further reduce supply noise coupling to the
oUtput.
Molded socket assemblies should be avoided even when proto-
typing circuits with the AD9712 or AD9713. When the DAC
cannot be directly soldered into the board, individual pin sock-
ets such as AMP #6-330808-0 (knock-out end), or #60330808-3
(open end) should be used. These have much less effect on
interlead capacitance than do molded assemblies.
-6- REV. A
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