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參數(shù)資料
| 型號： | TP3404 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Quad Digital Adapter for Subscriber Loops (QDASL) |
| 中文描述： | 四適配器數(shù)字用戶環(huán)路（QDASL） |
| 文件頁數(shù)： | 6/14頁 |
| 文件大?。?/td> | 212K |
| 代理商： | TP3404 |
Functional Description
(Continued)
Pulse shaping is obtained by means of a Digital to Analog
Converter followed by a Continuous Smoothing Filter, in or-
der to limit RF energy and crosstalk while minimizing Inter-
Symbol Interference (ISI). Figure 2 shows the pulse shape
at the Lo output, while a template for the typical power
spectrum transmitted to the line with random data is shown
in Figure 3.
Each line-driver output, Lo0–Lo3, is designed to drive a
transformer through a capacitor and termination resistor. A
1:1 transformer, terminated in 100
X
, results in signal ampli-
tude of typically 1.3 Vpk on the line. Over-voltage protection
must be included in each interface circuit.
LINE RECEIVE SECTIONS
The input of each receive section, Li0–Li3, consists of a
continuous anti-alias filter followed by a switched-capacitor
low-pass filter designed to limit the noise bandwidth with
minimum intersymbol interference. To correct pulse attenu-
ation and distortion caused by the transmission line an AGC
circuit and first-order equalizer adapt to the received pulse
shape, thus restoring a ‘‘flat’’ channel response with maxi-
mum received eye opening over a wide spread of cable
attenuation characteristics.
From the equalized output a DPLL (Digital Phase-Locked
Loop) recovers a low-jitter clock for optimum sampling of
the received symbols. The MCLK input provides the refer-
ence clock for the DPLL at 4.096 MHz.
Following detection of the recovered symbols, the received
data is de-scrambled by the same X
9
a
X
5
a
1 polynomial
and presented to the digital system interface circuit.
When a transmission line is de-activated, a Line-Signal De-
tect Circuit is enabled to detect the presence of incoming
bursts if the far-end starts to activate the loop.
TL/H/11924–4
FIGURE 2. Typical AMI Waveform at Lo
TL/H/11924–5
FIGURE 3. Typical AMI Transmit Spectrum Measured at LO Output (With RGB
e
100 Hz)
6
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| TP3404V | 功能描述:ISDN 接口 RoHS:否 制造商:Texas Instruments 封裝:Tube |
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| TP3406 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:DASL Digital Adapter for Subscriber Loops |
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