參數(shù)資料
型號： AD9709ASTZRL
廠商： Analog Devices Inc
文件頁數(shù)： 11/32頁
文件大?。?/td> 0K
描述： IC DAC 8BIT DUAL 125MSPS 48LQFP
產(chǎn)品培訓(xùn)模塊： Data Converter Fundamentals
DAC Architectures
標準包裝： 2,000
系列： TxDAC+®
設(shè)置時間： 35ns
位數(shù)： 8
數(shù)據(jù)接口： 并聯(lián)
轉(zhuǎn)換器數(shù)目： 2
電壓電源： 模擬和數(shù)字
功率耗散（最大）： 450mW
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 48-LQFP
供應(yīng)商設(shè)備封裝： 48-LQFP（7x7）
包裝： 帶卷 (TR)
輸出數(shù)目和類型： 4 電流，單極；4 電流，雙極
采樣率（每秒）： 125M
配用： AD9709-EBZ-ND - BOARD EVAL FOR AD9709
AD9709
Rev. B | Page 19 of 32
APPLYING THE AD9709
OUTPUT CONFIGURATIONS
The following sections illustrate some typical output configura-
tions for the AD9709. Unless otherwise noted, it is assumed that
IOUTFS is set to a nominal 20 mA. For applications requiring the
optimum dynamic performance, a differential output
configuration is suggested. A differential output configuration
can consist of either an RF transformer or a differential op amp
configuration. The transformer configuration provides the
optimum 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, 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 results
if IOUTA and/or IOUTB is connected to an appropriately sized load
resistor, RLOAD, 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 can be
configured as an I-V converter, thus converting IOUTA or IOUTB into a
negative unipolar voltage. This configuration provides the best dc
linearity because IOUTA or IOUTB is maintained at a virtual ground.
Note that IOUTA provides slightly better performance than IOUTB.
DIFFERENTIAL COUPLING USING A
TRANSFORMER
An RF transformer can be used as shown in Figure 36 to perform
a differential-to-single-ended signal conversion. A differentially
coupled transformer output provides the optimum distortion
performance for output signals whose spectral content lies within
the pass band of the transformer. An RF transformer such as the
Mini-Circuits T1-1T provides excellent rejection of common-
mode distortion (that is, 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 can also be used for impedance
matching purposes. Note that the transformer provides ac
coupling only.
RLOAD
AD9709
IOUTA
IOUTB
Mini-Circuits
T1-1T
OPTIONAL
RDIFF
00
60
6-
03
5
Figure 36. 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 IOUTA and IOUTB. The complementary voltages appearing
at IOUTA and IOUTB (that is, VOUTA and VOUTB) swing symmetrically
around ACOM and should be maintained with the specified
output compliance range of the AD9709. A differential resistor,
RDIFF, can be inserted in applications where the output of the
transformer is connected to the load, RLOAD, via a passive
reconstruction filter or cable. RDIFF 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 RDIFF.
DIFFERENTIAL COUPLING USING AN OP AMP
An op amp can also be used as shown in Figure 37 to perform a
differential-to-single-ended conversion. The AD9709 is configured
with two equal load resistors, RLOAD, of 25 Ω each. The differential
voltage developed across IOUTA and IOUTB is converted to a single-
ended signal via the differential op amp configuration. An optional
capacitor can be installed across IOUTA and IOUTB, forming a real pole
in a low-pass filter. The addition of this capacitor also enhances the
op amp’s distortion performance by preventing the DAC’s high-
slewing output from overloading the op amp’s input.
AD9709
500
500
225
25
25
AD8047
IOUTA
IOUTB
225
COPT
0
060
6-
0
36
Figure 37. DC Differential Coupling Using an Op Amp
The common-mode rejection of this configuration is typically
determined by the resistor matching. In this circuit, the differential
op amp circuit using the AD8047 is configured to provide some
additional signal gain. The op amp must operate from a dual
supply because 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 (that is,
cost and power) should be selected. The op amp’s differential
gain, gain setting resistor values, and full-scale output swing
capabilities should be considered when optimizing this circuit.
The differential circuit shown in Figure 38 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 used to level shift the differential
output of the AD9709 to midsupply (that is, AVDD/2). The
AD8041 is a suitable op amp for this application.
AD9709
500
500
225
25
25
AD8041
IOUTA
IOUTB
225
COPT
AVDD
1k
0
06
06-
0
37
Figure 38. Single-Supply DC Differential Coupled Circuit
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD9709ASTZRL1 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
AD9709-EB 制造商:Analog Devices 功能描述: 制造商:Rochester Electronics LLC 功能描述:
AD9709-EBZ 功能描述:BOARD EVAL FOR AD9709 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 數(shù)模轉(zhuǎn)換器 (DAC) 系列:TxDAC® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:1 系列:- DAC 的數(shù)量:4 位數(shù):12 采樣率（每秒）:- 數(shù)據(jù)接口:串行，SPI? 設(shè)置時間:3µs DAC 型:電流/電壓 工作溫度:-40°C ~ 85°C 已供物品:板 已用 IC / 零件:MAX5581
AD9709-EBZ1 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
AD9712 制造商:AD 制造商全稱:Analog Devices 功能描述:12-BIT, 100MSPS D/A CONVERTERS
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