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參數(shù)資料
| 型號(hào)： | AD97651 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 12-Bit, 125 MSPS Dual TxDAC+ D/A Converter |
| 中文描述： | 12位，125 MSPS的TxDAC系列雙D / A轉(zhuǎn)換 |
| 文件頁數(shù)： | 18/28頁 |
| 文件大?。?/td> | 472K |
| 代理商： | AD97651 |
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REV. B
AD9765
–18–
I and Q digital data can be fed into the AD9765 in two different
ways. In dual port mode, The digital I information drives one
input port, while the digital Q information drives the other input
port. If no interpolation filter precedes the DAC, the symbol
rate will be the rate at which the system clock drives the CLK
and WRT pins on the AD9765. In interleaved mode, the digital
input stream at Port 1 contains the I and the Q information in
alternating digital words. Using IQSEL and IQRESET, the
AD9765 can be synchronized to the I and Q data stream. The
internal timing of the AD9765 routes the selected I and Q data
to the correct DAC output. In interleaved mode, if no interpola-
tion filter precedes the AD9765, the symbol rate will be half that
of the system clock driving the digital data stream and the
IQWRT and IQCLK pins on the AD9765.
CDMA
Carrier Division Multiple Access, or CDMA, is an air transmit/
receive scheme where the signal in the transmit path is modu-
lated with a pseudorandom digital code (sometimes referred to
as the spreading code). The effect of this is to spread the trans-
mitted signal across a wide spectrum. Similar to a DMT wave-
form, a CDMA waveform containing multiple subscribers can
be characterized as having a high peak to average ratio (i.e.,
crest factor), thus demanding highly linear components in the
transmit signal path. The bandwidth of the spectrum is defined
by the CDMA standard being used, and in operation is imple-
mented by using a spreading code with particular characteristics.
Distortion in the transmit path can lead to power being trans-
mitted out of the defined band. The ratio of power transmitted
in-band to out-of-band is often referred to as Adjacent Channel
Power (ACP). This is a regulatory issue due to the possibility of
interference with other signals being transmitted by air. Regula-
tory bodies define a spectral mask outside of the transmit band,
(
“
Q DAC
”
)
IOUTA
QOUTA
QOUTB
DCOM
FSADJ2
REFIO
SLEEP
R
1.9k
0.1 F
CLK2
Q DATA
INPUT
I DATA
INPUT
DVDD
AVDD
500
50
500
500
IIPP
IIPN
IIQP
IIQN
AD6122
CLK1
FSADJ1
R
SET1
2k
R
CAL
220
500
INPUT
LATCHES
50
500
50
500
50
DAC
LATCH
DAC
(
“
I DAC
”
)
INPUT
LATCHES
WRT1
WRT2
ACOM
AD9765
U1
U2
LOIPP
LOIPN
2
PHASE
SPLITTER
REFIN
VGAIN
GAIN
CONTROL
TXOPP
TXOPN
GAIN
CONTROL
SCALE
FACTOR
TEMPERATURE
COMPENSATION
MODOPN
MODOPP
VCC
VCC
+3V
500
500
IOUTB
DAC
DAC
LATCH
634
Figure 44. CDMA Transmit Application Using AD9765 and AD6122
and the ACP must fall under this mask. If distortion in the
transmit path causes the ACP to be above the spectral mask,
then filtering, or different component selection, is needed to
meet the mask requirements.
Figure 43 shows the AD9765, when used with the AD8346,
reconstructing a wideband CDMA signal at 2.4 GHz. The
baseband signal is being sampled at 65 MSPS and has a chip
rate of 8M chips.
==
–
80
–
120
–
70
–
90
–
110
–
50
–
60
–
100
–
40
CENTER 2.4GHz
3MHz
SPAN 30MHz
–
130
–
30
d
c11
cu1
C0
C0
c11
FREQUENCY
Figure 43. CDMA Signal, 8 M Chips Sampled at 65 MSPS,
Recreated at 2.4 GHz, Adjacent Channel Power > 60 dBm
Figure 44 shows an example of the AD9765 used in a W-CDMA
transmitter application using the AD6122 CDMA 3 V IF sub-
system. The AD6122 has functions, such as external gain con-
trol and low distortion characteristics, needed for the superior
Adjacent Channel Power (ACP) requirements of W-CDMA.
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| AD9765ASTZ | 功能描述:IC DAC 12BIT DUAL 125MSPS 48LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 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:50 系列:- 設(shè)置時(shí)間:4µs 位數(shù):12 數(shù)據(jù)接口:串行 轉(zhuǎn)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(yīng)商設(shè)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(chǎn)品目錄頁面:1398 (CN2011-ZH PDF) |
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| AD9765ASTZKL1 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
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