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| 型號(hào)： | AD9764-EB |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 14-Bit, 125 MSPS TxDAC D/A Converter |
| 中文描述： | 14位，125 MSPS的TxDAC系列D / A轉(zhuǎn)換 |
| 文件頁(yè)數(shù)： | 14/22頁(yè) |
| 文件大?。?/td> | 307K |
| 代理商： | AD9764-EB |
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REV. B
AD9764
–14–
APPLYING THE AD9764
OUTPUT CONFIGURATIONS
The following sections illustrate some typical output configura-
tions for the AD9764. 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.
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 configura-
tion 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, 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
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 com-
mon-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. Trans-
formers with different impedance ratios may also be used for
impedance matching purposes. Note that the transformer
provides ac coupling only.
R
LOAD
AD9764
22
21
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 appear-
ing at I
OUTA
and I
OUTB
(i.e., V
OUTA
and V
OUTB
) swing sym-
metrically around ACOM and should be maintained with the
specified output compliance range of the AD9764. A differential
resistor, R
DIFF
, may be inserted in applications in which 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 approxi-
mately half the signal power will be dissipated across R
DIFF
.
DIFFERENTIAL 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 AD9764 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 amp’s distortion perfor-
mance by preventing the DAC’s high slewing output from over-
loading the op amp’s input.
AD9764
22
I
OUTA
I
OUTB
21
C
OPT
500
V
225
V
225
V
500
V
25
V
25
V
AD8047
Figure 34. 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 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 perform-
ance of the AD9764 while meeting other system level objectives
(i.e., cost, power) should be selected. The op amps differential
gain, its gain setting resistor values and full-scale output swing
capabilities should all be considered when optimizing this circuit.
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
AD9764 and the op amp, is also used to level-shift the differ-
ential output of the AD9764 to midsupply (i.e., AVDD/2). The
AD8041 is a suitable op amp for this application.
AD9764
22
I
OUTA
I
OUTB21
C
OPT
500
V
225
V
225
V
1k
V
25
V
25
V
AD8041
1k
V
AVDD
Figure 35. Single-Supply DC Differential Coupled Circuit
SINGLE-ENDED UNBUFFERED VOLTAGE OUTPUT
Figure 36 shows the AD9764 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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參數(shù)描述 |
|---|---|
| AD9764-EBZ | 功能描述:BOARD EVAL FOR AD9764 RoHS:是 類別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)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(biāo)準(zhǔn)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(shí)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 |
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| AD9765AST | 功能描述:數(shù)模轉(zhuǎn)換器- DAC 12-Bit 125 MSPS Dual TxDAC+ RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| AD9765ASTRL | 制造商:Analog Devices 功能描述:DAC 2-CH Segment 12-bit 48-Pin LQFP T/R 制造商:Analog Devices 功能描述:DAC DUAL CURRENT STEERING 12-BIT 48LQFP - Tape and Reel 制造商:Rochester Electronics LLC 功能描述:12-BIT, 125 MSPS DUAL TXDAC+ - Tape and Reel 制造商:Analog Devices Inc. 功能描述:Digital to Analog Converters - DAC 12-Bit 125 MSPS Dual TxDAC+ 制造商:Analog Devices Inc. 功能描述:Digital to Analog Converters - DAC 12-Bit 125 MSPS Dual 制造商:Analog Devices 功能描述:CONVERTER - DAC |
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