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參數(shù)資料
| 型號： | AD9767 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 14-Bit, 125 MSPS Dual TxDAC+ D/A Converter |
| 中文描述： | 14位，125 MSPS的TxDAC系列雙D / A轉換 |
| 文件頁數(shù)： | 14/27頁 |
| 文件大?。?/td> | 469K |
| 代理商： | AD9767 |
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REV. B
AD9767
–14–
APPLYING THE AD9767
Output Configurations
The following sections illustrate some typical output configura-
tions for the AD9767. Unless otherwise noted, it is assumed
that I
OUTFS
is set to a nominal 20 mA. For applications requir-
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
bandwidth 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
OUTA
and/or I
OUTB
is connected to an appropriately-
sized load resistor, R
LOAD
, referred to ACOM. This configuration
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 convert-
ing I
OUTA
or I
OUTB
into a negative unipolar voltage. This con-
figuration provides the best dc linearity since I
OUTA
or I
OUTB
is maintained at a virtual ground. Note that I
OUTA
provides
slightly better performance than I
OUTB
.
DIFFERENTIAL COUPLING USING A TRANSFORMER
An RF transformer can be used to perform a differential-to-
single-ended signal conversion as shown in Figure 33. A dif-
ferentially coupled transformer output provides the optimum
distortion performance for output signals whose spectral con-
tent 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.
Transformers with different impedance ratios may also be used
for impedance matching purposes. Note that the transformer
provides ac coupling only.
The center tap on the primary side of the transformer must be
connected to ACOM to provide the necessary dc current path
for both I
OUTA
and I
OUTB
. The complementary voltages appear-
ing at I
OUTA
and I
OUTB
(i.e., V
OUTA
and V
OUTB
) swing symmetri-
cally around ACOM and should be maintained with the specified
output compliance range of the AD9767. A differential resistor,
R
DIFF
, may be inserted in applications where the output of the
transformer is connected to the load, R
LOAD
, via a passive
reconstruction filter or cable. R
DIFF
is determined by the trans-
former’s impedance ratio and provides the proper source termi-
nation that results in a low VSWR. Note that approximately half
the signal power will be dissipated across R
DIFF
.
R
LOAD
AD9767
MINI-CIRCUITS
T1-1T
OPTIONAL
R
DIFF
I
OUTA
I
OUTB
Figure 33. Differential Output Using a Transformer
DIFFERENTIAL COUPLING USING AN OP AMP
An op amp can also be used to perform a differential-to-single-
ended conversion as shown in Figure 34. The AD9767 is con-
figured with two equal load resistors, R
LOAD
, of 25
. The
differential voltage developed across I
OUTA
and I
OUTB
is con-
verted to a single-ended signal via the differential op amp con-
figuration. An optional capacitor can be installed across I
OUTA
and I
OUTB
, forming a real pole in a low-pass filter. The addition
of this capacitor also enhances the op amps distortion perfor-
mance by preventing the DACs high slewing output from over-
loading the op amp’s input.
The common-mode rejection of this configuration is typically
determined by the resistor matching. In this circuit, the differ-
ential op amp circuit using the AD8047 is configured to provide
some additional signal gain. The op amp must operate from a
dual supply since its output is approximately
±
1.0 V. A high
speed amplifier capable of preserving the differential perfor-
mance of the AD9767, while meeting other system level
objectives (i.e., cost, power), should be selected. The op
amp’s differential gain, its gain setting resistor values, and
full-scale output swing capabilities should all be considered
when optimizing this circuit.
AD9767
I
OUTA
I
OUTB
500
225
225
500
25
25
AD8047
C
OPT
Figure 34. DC Differential Coupling Using an Op Amp
The differential circuit shown in Figure 35 provides the neces-
sary level-shifting required in a single supply system. In this case
AVDD, which is the positive analog supply for both the AD9767
and the op amp, is also used to level-shift the differential output
of the AD9767 to midsupply (i.e., AVDD/2). The AD8055 is a
suitable op amp for this application.
AD9767
I
OUTA
I
OUTB
C
OPT
500
225
225
500
25
25
AD8055
1k
AVDD
Figure 35. Single Supply DC Differential Coupled Circuit
SINGLE-ENDED UNBUFFERED VOLTAGE OUTPUT
Figure 36 shows the AD9767 configured to provide a unipolar
output range of approximately 0 V to +0.5 V for a doubly termi-
nated 50
cable since the nominal full-scale current, I
OUTFS
, of
20 mA flows through the equivalent R
LOAD
of 25
. In this case,
R
LOAD
represents the equivalent load resistance seen by I
OUTA
or
I
OUTB
. The unused output (I
OUTA
or I
OUTB
) can be connected to
ACOM directly or via a matching R
LOAD
. Different values of
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| AD9767-EB | 14-Bit, 125 MSPS Dual TxDAC+ D/A Converter |
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD9767AST | 制造商:Analog Devices 功能描述:DAC 2-CH Segment 14-bit 48-Pin LQFP 制造商:Rochester Electronics LLC 功能描述:14-BIT, 125 MSPS DUAL TXDAC+ - Tape and Reel 制造商:Analog Devices 功能描述:IC 14-BIT DAC |
| AD9767ASTRL | 制造商:Analog Devices 功能描述:DAC 2-CH Segment 14-bit 48-Pin LQFP T/R 制造商:Rochester Electronics LLC 功能描述:14-BIT, 125 MSPS DUAL TXDAC+ - Tape and Reel |
| AD9767ASTZ | 功能描述:IC DAC 14BIT DUAL 125MSPS 48LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據采集 - 數(shù)模轉換器 系列:TxDAC+® 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 設置時間:4µs 位數(shù):12 數(shù)據接口:串行 轉換器數(shù)目:2 電壓電源:單電源 功率耗散（最大）:- 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬） 供應商設備封裝:8-uMAX 包裝:管件 輸出數(shù)目和類型:2 電壓，單極 采樣率（每秒）:* 產品目錄頁面:1398 (CN2011-ZH PDF) |
| AD9767ASTZ | 制造商:Analog Devices 功能描述:D/A CONVERTER (D-A) IC ((NW)) |
| AD9767ASTZAIRBUS | 制造商:Analog Devices 功能描述: |
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