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參數資料
| 型號： | AD9754* |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 14-Bit. 125 MSPS High Performance TxDAC D/A Converter |
| 中文描述： | 14位。 125 MSPS的TxDAC系列高性能D / A轉換 |
| 文件頁數： | 17/24頁 |
| 文件大小： | 327K |
AD9754
–17–
REV. A
f
CLOCK
/4). This particular multitone vector, has a peak-to-rms
ratio of 13.5 dB compared to a sine waves peak-to-rms ratio of
3 dB. A “snapshot” of this reconstructed multitone vector in the
time domain as shown in Figure 34b reveals the higher signal
content around the midscale value. As a result, a DAC’s “small-
scale” dynamic and static linearity becomes increasingly criti-
cal in obtaining low intermodulation distortion and maintaining
sufficient carrier-to-noise ratios for a given modulation scheme.
A DAC’s small-scale linearity performance is also an important
consideration in applications where additive dynamic range is
required for gain control purposes or “predistortion” signal
conditioning. For instance, a DAC with sufficient dynamic
range can be used to provide additional gain control of its
reconstructed signal. In fact, the gain can be controlled in
6 dB increments by simply performing a shift left or right on the
DAC’s digital input word. Other applications may intentionally
TIME
1.0000
0.8000
–1.0000
V
–0.2000
–0.4000
–0.6000
–0.8000
0.2000
0.0000
0.4000
0.6000
Figure 34b. Time Domain “Snapshot” of the Multitone
Waveform
predistort a DAC’s digital input signal to compensate for
nonlinearities associated with the subsequent analog compo-
nents in the signal chain. For example, the signal compression
associated with a power amplifier can be compensated for by
predistorting the DAC’s digital input with the inverse nonlinear
transfer function of the power amplifier. In either case, the
DAC’s performance at reduced signal levels should be carefully
evaluated.
A full-scale single tone will induce all of the dynamic and static
nonlinearities present in a DAC that contribute to its distortion
and hence SFDR performance. Referring to Figure 3, as the
frequency of this reconstructed full-scale, single-tone waveform
increases, the dynamic nonlinearities of any DAC (i.e., AD9754)
tend to dominate thus contributing to the roll-off in its SFDR
performance. However, unlike most DACs, which employ an R-2R
ladder for the lower bit current segmentation, the AD9754 (as
well as other TxDAC members) exhibits an improvement in
distortion performance as the amplitude of a single tone is re-
duced from its full-scale level. This improvement in distortion
performance at reduced signal levels is evident if one compares
the SFDR performance vs. frequency at different amplitudes
(i.e., 0 dBFS, –6 dBFS and –12 dBFS) and sample rates as
shown in Figures 4 through 7. Maintaining decent “small-scale”
linearity across the full span of a DAC transfer function is also
critical in maintaining excellent multitone performance.
Although characterizing a DAC’s multitone performance tends
to be application-specific, much insight into the potential perfor-
mance of a DAC can also be gained by evaluating the DAC’s
swept power (i.e., amplitude) performance for single, dual and
multitone test vectors at different clock rates and carrier frequen-
cies. The DAC is evaluated at different clock rates when recon-
structing a specific waveform whose amplitude is decreased in
3 dB increments from full-scale (i.e., 0 dBFS). For each specific
waveform, a graph showing the SFDR (over Nyquist) perfor-
mance vs. amplitude can be generated at the different tested
clock rates as shown in Figures 9–11. Note that the carrier(s)-to-
clock ratio remains constant in each figure. In each case, an
improvement in SFDR performance is seen as the amplitude is
reduced from 0 dBFS to approximately –9.0 dBFS.
A multitone test vector may consist of several equal amplitude,
spaced carriers each representative of a channel within a defined
bandwidth as shown in Figure 37a. In many cases, one or more
tones are removed so the intermodulation distortion performance
of the DAC can be evaluated. Nonlinearities associated with the
DAC will create spurious tones of which some may fall back into
the “empty” channel thus limiting a channel’s carrier-to-noise
ratio. Other spurious components falling outside the band of
interest may also be important, depending on the system’s spectral
mask and filtering requirements.
This particular test vector was centered around one-half the
Nyquist bandwidth (i.e., f
CLOCK
/4) with a passband of f
CLOCK
/16.
Centering the tones at a much lower region (i.e., f
CLOCK
/10)
would lead to an improvement in performance while centering
the tones at a higher region (i.e., f
CLOCK
/2.5) would result in a
degradation in performance.
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相關代理商/技術參數 |
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| AD9754AR | 功能描述:IC DAC 14BIT 125MSPS HP 28-SOIC RoHS:否 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:Data Converter Fundamentals DAC Architectures 標準包裝:750 系列:- 設置時間:7µs 位數:16 數據接口:并聯 轉換器數目:1 電壓電源:雙 ± 功率耗散（最大）:100mW 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-LCC（J 形引線） 供應商設備封裝:28-PLCC（11.51x11.51） 包裝:帶卷 (TR) 輸出數目和類型:1 電壓，單極；1 電壓，雙極 采樣率（每秒）:143k |
| AD9754ARRL | 制造商:Analog Devices 功能描述:DAC 1-CH 14-bit 28-Pin SOIC W T/R 制造商:Rochester Electronics LLC 功能描述:14-BIT, 125 MSPS+ TXDAC D/A CONVERTER - Tape and Reel |
| AD9754ARU | 功能描述:IC DAC 14BIT 125MSPS 28-TSSOP RoHS:否 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:Data Converter Fundamentals DAC Architectures 標準包裝:750 系列:- 設置時間:7µs 位數:16 數據接口:并聯 轉換器數目:1 電壓電源:雙 ± 功率耗散（最大）:100mW 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-LCC（J 形引線） 供應商設備封裝:28-PLCC（11.51x11.51） 包裝:帶卷 (TR) 輸出數目和類型:1 電壓，單極；1 電壓，雙極 采樣率（每秒）:143k |
| AD9754ARURL7 | 功能描述:IC DAC 14BIT 125MSPS 28-TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 數模轉換器 系列:TxDAC® 標準包裝:47 系列:- 設置時間:2µs 位數:14 數據接口:并聯 轉換器數目:1 電壓電源:單電源 功率耗散（最大）:55µW 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:28-SSOP（0.209"，5.30mm 寬） 供應商設備封裝:28-SSOP 包裝:管件 輸出數目和類型:1 電流，單極；1 電流，雙極 采樣率（每秒）:* |
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