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參數資料
| 型號： | AD9709AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | DAC |
| 英文描述： | RES 0.01 OHM MAX 25 AMP AXIAL |
| 中文描述： | PARALLEL, 8 BITS INPUT LOADING, 0.035 us SETTLING TIME, 8-BIT DAC, PQFP48 |
| 封裝： | PLASTIC, LQFP-48 |
| 文件頁數： | 14/27頁 |
| 文件大小： | 466K |
| 代理商： | AD9709AST |
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REV. 0
AD9709
–14–
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 converting
I
OUTA
or I
OUTB
into a negative unipolar voltage. This configuration
provides the best dc linearity since I
OUTA
or I
OUTB
is maintained at
a virtual ground. Note that I
OUTA
provides slightly better perfor-
mance 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
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.
Transformers with different impedance ratios may also be used
for impedance matching purposes. Note that the transformer
provides ac coupling only.
R
LOAD
AD9709
MINI-CIRCUITS
T1-1T
OPTIONAL
R
DIFF
I
OUTA
I
OUTB
Figure 33. Differential Output Using a Transformer
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 appearing
at I
OUTA
and I
OUTB
(i.e., V
OUTA
and V
OUTB
) swing symmetrically
around ACOM and should be maintained with the specified
output compliance range of the AD9709. 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
transformer’s impedance ratio and provides the proper source
termination that results in a low VSWR. Note that approximately
half the signal power will be dissipated across R
DIFF
.
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 AD9709 is
configured with two equal load resistors, R
LOAD
, of 25
. The
differential voltage developed across I
OUTA
and I
OUTB
is converted
to a single-ended signal via the differential op amp configuration.
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 performance by
preventing the DACs high-slewing output from overloading the
op amp’s input.
The common-mode rejection of this configuration is typically
determined by the resistor matching. In this circuit, the differen-
tial op amp circuit using the AD8047 is configured to provide
some additional signal gain. The op amp must operate off of a
dual supply since its output is approximately
±
1.0 V. A high-
speed amplifier capable of preserving the differential performance
of the AD9709 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 capa-
bilities should all be considered when optimizing this circuit.
The differential circuit shown in Figure 35 provides the necessary
level-shifting required in a single supply system. In this case,
AVDD which is the positive analog supply for both the AD9709
and the op amp is also used to level-shift the differential output
of the AD9709 to midsupply (i.e., AVDD/2). The AD8041 is a
suitable op amp for this application.
SINGLE-ENDED UNBUFFERED VOLTAGE OUTPUT
Figure 36 shows the AD9709 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
I
OUTFS
and R
LOAD
can be selected as long as the positive compli-
ance range is adhered to. One additional consideration in this
mode is the integral nonlinearity (INL) as discussed in the
Analog Output section of this data sheet. For optimum INL
performance, the single-ended, buffered voltage output configu-
ration is suggested.
AD9709
500
225
225
500
25
25
AD8047
C
OPT
I
OUTA
I
OUTB
Figure 34. DC Differential Coupling Using an Op Amp
AD9709
I
OUTA
I
OUTB
C
OPT
500
225
225
500
25
25
AD8041
1k
AVDD
Figure 35. Single Supply DC Differential Coupled Circuit
AD9709
50
I
OUTA
I
OUTB
Figure 36. 0 V to 0.5 V Unbuffered Voltage Output
相關PDF資料 |
PDF描述 |
|---|---|
| AD9709-EB | 8-Bit, 125 MSPS Dual TxDAC D/A Converter |
| AD9712B | RES,0.0,0.25W,METAL FILM,0% |
| AD9712BAN | RES,0.0,0.25W,METAL FILM,0% |
| AD9712BAP | TEST POINT, WHITE, 0.040 HOLE, 0.062 PCB |
| AD9712BBN | POWER JACK, 250V,2 COND. FEMALE,2.1MM |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD9709ASTRL | 制造商:Analog Devices 功能描述:DAC 2-CH Segment 8-bit 48-Pin LQFP T/R 制造商:Rochester Electronics LLC 功能描述:8-BIT 125 MSPS DUAL TXDAC+ D/A CONVERTER - Tape and Reel |
| AD9709ASTZ | 功能描述:IC DAC 8BIT DUAL 125MSPS 48-LQFP RoHS:是 類別:集成電路 (IC) >> 數據采集 - 數模轉換器 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:12 數據接口:串行 轉換器數目: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 輸出數目和類型:2 電壓，單極 采樣率（每秒）:* 產品目錄頁面:1398 (CN2011-ZH PDF) |
| AD9709ASTZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:8-Bit, 125 MSPS, Dual TxDAC Digital-to-Analog Converter |
| AD9709ASTZKL1 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| AD9709ASTZRL | 功能描述:IC DAC 8BIT DUAL 125MSPS 48LQFP RoHS:是 類別:集成電路 (IC) >> 數據采集 - 數模轉換器 系列:TxDAC+® 產品培訓模塊:LTC263x 12-, 10-, and 8-Bit VOUT DAC Family 特色產品:LTC2636 - Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference 標準包裝:91 系列:- 設置時間:4µs 位數:10 數據接口:MICROWIRE?，串行，SPI? 轉換器數目:8 電壓電源:單電源 功率耗散（最大）:2.7mW 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應商設備封裝:14-DFN-EP（4x3） 包裝:管件 輸出數目和類型:8 電壓，單極 采樣率（每秒）:* |
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