參數(shù)資料
型號(hào): AM7968
廠商: Advanced Micro Devices, Inc.
英文描述: TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
中文描述: TAXIchip集成電路(透明異步Xmitter,接收器接口)
文件頁數(shù): 66/127頁
文件大小: 730K
代理商: AM7968
AMD
62
TAXIchip Integrated Circuits Technical Manual
common mode range. The average DC value of the input signal is therefore relatively
unimportant.
There are three broad classes of TAXl-to-media interface:
1. Very short (<3
link length), usually DC coupled.
2. Terminated, DC coupled.
3. Terminated, AC coupled.
The short link is typical of a TAXIchip set to optical components connection. The
terminated cases are used for driving cables, also optical or other components with
incompatible power supply and/or logic level requirements may sometimes need circuits
and layout that exceed 3
.
5.1 V ery S hort Link, DC Coupled
For DC coupled inter-connections in which the distance between the serial pins and the
next device is less than 3
, transmission line terminations are not necessary. All that is
required is an appropriate PECL pull-down resistor, RE. Elimination of reflections is not
required for these short line lengths because the round-trip propagation is significantly
less than the 2 ns TAXIchip set rise and fall time. The effect of media mismatch in this
case is distortion and slowing of the transition due to the addition of the reflection to the
still changing edge.
Figure 5-1a
S tandard Load Circ uit
V
OH
= 4.1 V
V
CC
–2 V = 3 V
I
OH
50
12330E-7
Figure 5-1b
Pull-Down with I
OH
Matc hed to S tandard Load
I
OH
RE
V
OH
= 4.1 V
C
12330E-8
The lower limit for
RE
is that value which produces the maximum value of l
OH
. In a
standard PECL load circuit (Figure 5-1a) l
OH
max is given by:
(V
OH
– (V
CC
–2))/50 = (4.1–3)/50 = 22 mA
If we return RE to ground instead of 3 V (Figure 5-1b), the minimum value of
RE
becomes 4.1 V/22 mA, or 186
.
Reflections due to mismatch can be minimized by locating the pull-down resistor at the
end of the line, rather than the source. A mismatched line termination will give a
reflection coefficient less than one while leaving the end of the line open will give a
reflection coefficient of one (maximum reflection). Note that the supply voltage and logic
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AM7968/AM7969 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:Am7968/Am7969 - TAXIchip Integrated Circuits: Transparent Asynchronous Transmitter/Receiver Interface
AM7968-100/B3A 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Transmitter
AM7968-100/BXA 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Transmitter
AM7968-100DC 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Transmitter