AN-555 Datasheet PDF - Analog Device
| Part Number | AN-555 | |
| Description | Application Note | |
| Manufacturers | Analog Device | |
| Logo |  |
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AN-555
APPLICATION NOTE
One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106 • 781/329-4700 • World Wide Web Site: http://www.analog.com
Using the AD9709, AD9763, AD9765, AD9767 Dual DAC Evaluation Board
By Steve Reine and Dawn Ostenberg
GENERAL DESCRIPTION
The AD9709, AD9763, AD9765 and AD9767 are high-
speed, high-performance dual DACs (8-, 10-, 12-, 14-
www.DataSheebt4itUs.)codmesigned for I/Q transmit applications and for appli-
cations where board space is at a premium. The
evaluation board allows the user to take full advantage
of the various modes in which the AD976x can operate.
This includes operation as dual DACs with their own indi-
vidual digital inputs, as well as interleaved DACs where
data is alternately written from digital input Port 1 to
either of the two DACs. Information on how to operate
the evaluation board is included in this application
note. However, for more detailed performance informa-
tion, the reader should consult the individual data
sheets for the AD9709, AD9763, AD9765, and AD9767.
WORD
GENERATOR
CLOCK
SOURCE
DIGITAL
DATA BUS
CLK
DATA IN
DUAL DAC
EVALUATION
BOARD
AVDD
DVDD
DATA
OUT
OSCILLOSCOPE
SPECTRUM
ANALYZER
ACOM DCOM
ANALOG
VDD
(3V TO 5V)
DIGITAL
VDD
(3V TO 5V)
Figure 1. Typical Test Setup to Evaluate Performance
of AD976x Dual DAC Using Evaluation Board
The 8-, 10-, 12-, and 14-bit DACs in this family are all pin-
for-pin-compatible and are MSB justified. Therefore, the
same evaluation board can be used to evaluate all
four parts.
EVALUATION SETUP
To evaluate the performance of the AD976x dual DAC
family, a small set of measurement and signal genera-
tion equipment is needed. Figure 1 shows a typical test
setup. Power supplies capable of driving from 3 V to 5 V
are needed for both analog and digital circuitry on the
evaluation board. A signal generator and digital word
generator are needed to provide the data and clock
inputs. On the output, an oscilloscope or spectrum
analyzer may be needed, depending on the type of per-
formance being analyzed.
TP10
L1
DVDDIN
BEAD
BAN-JACK
DVDD
C9
10F
25V
TP37 TP38 TP39
POWER CONNECTIONS
The AD9709, AD9763, AD9765, AD9767 dual DACs all
have separate digital and analog power and ground
pins. Analog and digital power and ground have their own
banana-style connectors on the dual DAC evaluation
board. The best performance when using the evaluation
board is achieved when analog and digital power and
ground are connected to separate power supplies.
Figure 2 shows the power supply, grounding, and decou-
pling connections for the evaluation board and for the
DAC itself. Note that for best noise rejection on the
power supplies, the high value bulk capacitors are
placed at the external power connectors, while the
smaller value capacitors, needed for high frequency
rejection, are located close to the DAC.
TP11
L2 AVDD
AVDDIN
BEAD
BAN-JACK
C10
10F
25V
TP40 TP41 TP42
BAN-JACK
DVDD
C1
0.001F
C2
0.01F
C3
0.1F
TP43
DGND
BAN-JACK
DVDD1 DVDD2 AVDD
DCOM1
DCOM2
AD9709
AD9763
AD9765
AD9767
DUAL DAC
ACOM
C13
0.1F
AVDD
TP44
C12
0.01F
C11
0.001F
AGND
Figure 2. Analog and Digital Power Connections on Dual DAC Evaluation Board
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REFIO (C14) may need to be removed under these condi-
tions. Figures 7 and 8 show the internal and external ref-
erence configurations for the AD9709, AD9763, AD9765,
and AD9767.
When using an external reference in this way, the full-
scale output current for each DAC can be defined by;
IOUTFS = 32 × VREF/REXT
Note that in the internal reference configuration, any
additional load on the reference should be buffered with
an external amplifier. This external amplifier is not
included on the evaluation board.
www.DataSheeFt4oUr.cmomore detailed information on the operation of the
reference section of the DACs, see page 9 of the data
sheet.
OPTIONAL
EXTERNAL
REFERENCE
BUFFER
ADDITIONAL
EXTERNAL
LOAD
GAINCTRL
0.1F
+1.2V REF
REFIO
FSADJ
IREF 2k⍀
AVDD
DUAL DAC
REFERENCE
SECTION
CURRENT
SOURCE
ARRAY
ACOM
Figure 7. Internal Reference Configuration
GAINCTRL
AVDD
EXTERNAL
REFERENCE
+1.2V REF
REFIO
FSADJ
IREF 2k⍀
AVDD
DUAL DAC
REFERENCE
SECTION
CURRENT
SOURCE
ARRAY
ACOM
Figure 8. External Reference Configuration
MASTER/SLAVE RESISTOR MODE, GAINCTRL
The AD9709, AD9763, AD9765, AD9767 all allow the gain
of each channel to be independently set by connecting
one RSET resistor to FSADJ1 and another RSET resistor to
FSADJ2. To add flexibility and reduce system cost, a
single RSET resistor can be used to set the gain of both
channels simultaneously.
When GAINCTRL is low (i.e., connected to AGND), the
independent channel gain control mode using two resis-
tors is enabled. In this mode, individual RSET resistors
should be connected to FSADJ1 and FSADJ2. When
GAINCTRL is high (i.e., connected to AVDD), the master/
slave channel gain control mode using one resistor is
AN-555
enabled. In this mode, a single RSET resistor is connected
to FSADJ1 and the resistor on FSADJ2 can be removed.
Note: Only parts with date code of 9930 or later have the
Master/Slave GAINCTRL function. For parts prior to this
date code, Pin 42 must be connected to AGND, and the
part will operate in the two resistor, independent gain
control mode.
OUTPUT CONFIGURATION
The AD9709, AD9763, AD9765, AD9767 have been
designed to achieve optimum performance with the
outputs used differentially. A transformer on the evalua-
tion board (Mini-Circuits T1–1T) allows the conversion
of the differential outputs to a single-ended signal. The
bandwidth of this transformer allows low distortion
operation from 350 kHz to well past the Nyquist bandwidth
of the DAC when operating at its highest sampling rate.
Figure 9 shows a typical DAC output configuration. Both
outputs drive a 50 Ω resistor as well as a transformer.
The grounded centertap on the primary of the trans-
former causes the output of the DAC to swing around
ground, allowing for wider p-p swing while still remain-
ing within the output voltage compliance range of the
DAC. On the evaluation board, these resistors are R5,
R6, R7, and R8. This provides a full-scale differential out-
put voltage of 0.67 V p-p when operating with IOUTFS =
20 mA and the transformer terminated with 50 Ω.
If the secondary of the transformer is terminated with
50 Ω, the DAC will then be capable of driving 0.5 dBm
into this load at full-scale out.
C4, C5, C6, and C15 (10 pF) on the evaluation board,
working together with the 50 Ω output resistors, form a
low-pass filter which gives some amount of image rejec-
tion at higher output frequencies. In applications where
an amplifier is used in place of the transformer, it is
important that the capacitor values be chosen to limit
the output slew rate of the DAC. If the output of the
amplifier becomes slew rate limited, severe distortion
can result.
IOUT
AD9709
AD9763
AD9765
AD9767 IOUT
10pF 50⍀ 50⍀ 10pF
50⍀
Figure 9. Typical DAC Output Configuration
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for AN-555 electronic component. |
| Information | Total 12 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ AN-555.PDF Datasheet ] | |
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