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參數(shù)資料
| 型號： | L8575 |
| 英文描述： | Dual-Resistive,Low-Cost Subscriber Line Interface Circuit(SLIC) |
| 中文描述： | 雙電阻，低成本用戶線接口電路（SLIC） |
| 文件頁數(shù)： | 28/36頁 |
| 文件大?。?/td> | 633K |
| 代理商： | L8575 |
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L8575
Dual-Resistive, Low-Cost SLIC
Advance Data Sheet
March 1997
28
Lucent Technologies Inc.
ac Design
Codec Features and Selection Summary
There are four key ac design parameters:
I
Termination impedanceis the impedance looking
into the 2-wire port of the line card. It is set to match
the impedance of the telephone loop in order to mini-
mize echo return to the telephone set.
I
Transmit gainis measured from the 2-wire port to the
PCM highway.
I
Receive gainis done from the PCM highway to the
transmit port.
I
Hybrid balance networkcancels the unwanted
amount of the receive signal that appears at the
transmit port.
At this point in the design, the codec needs to be select-
ed. The discrete network between the SLIC and the co-
dec can then be designed. Below is a brief codec
feature and selection summary.
First-Generation Codecs
These perform the basic filtering, A/D (transmit), D/A
(receive), and
μ
-law/A-law companding. They all have
an op amp in front of the A/D converter for transmit gain
setting and hybrid balance (cancellation at the summing
node). Depending on the type, some have differential
analog input stages, differential analog output stages,
and
μ
-law/A-law selectability. This generation of codec
has the lowest cost. It is most suitable for applications
with fixed gains, termination impedance, and hybrid
balance.
Second-Generation Codecs
This class of devices includes a microprocessor inter-
face for software control of the gains and hybrid bal-
ance. The hybrid balance is included in the device. ac
programmability adds application flexibility and saves
several passive components. It also adds several I/O
latches that are needed in the application. It does not
have the transmit op amp, since the transmit gain and
hybrid balance are set internally.
Third-Generation Codecs
This class of devices includes the gains, termination im-
pedance, and hybrid balance—all under microproces-
sor control. Depending on the device, it may or may not
include latches.
In the codec selection, increasing software control and
flexibility are traded for device cost. To help decide, it
may be useful to consider the following:
I
Will the application require only one value for each
gain and impedance
I
Will the board be used in different countries with dif-
ferent requirements
I
Will several versions of the board be built If so, will
one version of the board be most of the production
volume
I
Does the application need only real termination
impedance
I
Does the hybrid balance need to be adjusted in the
field
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| L8576B | Dual Ringing SLIC |
| L8712(FECONLY) | IC TUBE FOR TO-220 508MM |
| L88R05_SERIES | |
| L8958-11SC | Optoelectronic |
| L8958-12FC | Optoelectronic |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L8576B | 制造商:AGERE 制造商全稱:AGERE 功能描述:Dual Ringing SLIC |
| L8576BP | 制造商:Alcatel-Lucent 功能描述: 制造商:LUCENT 功能描述: |
| L85J250E | 制造商:Ohmite Mfg Co 功能描述: |
| L8601-01 | 制造商:HAMAMATSU 制造商全稱:Hamamatsu Corporation 功能描述:90KV MICROFOCUS X-RAY SOURCE |
| L8605 | 制造商:Leviton Manufacturing Co 功能描述: |
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