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參數資料
| 型號： | AD8178 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| 中文描述： | 450兆赫，三16】5視頻交叉點開關 |
| 文件頁數： | 36/40頁 |
| 文件大小： | 545K |
| 代理商： | AD8178 |
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AD8178
on the propagation speed (V
P
) of the signal in the chosen board
material and the distance (d) between the termination resistor
and the AD8178. If the distance is great enough, these peaks can
occur in-band. In fact, practical experience shows that these
peaks are not high Q and should be pushed out to three or four
times the desired bandwidth to not have an effect on the signal.
For a board designer using FR4 (V
P
= 144 × 10
6
m/sec), this
means the AD8178 should be no more than 1.5 cm after the
termination resistors and should preferably be placed even closer.
The BGA substrate routing inside the AD8178 is approximately
1 cm in length and adds to the stub length, so 1.5 cm PCB routing
equates to d = 2.5 × 10
–2
m in the calculations.
(
)
d
4
where
n
= {0, 1, 2, 3, ...}.
In some cases, it is difficult to place the termination close to the
AD8178 due to space constraints, differential routing, and large
resistor footprints. A preferable solution in this case is to maintain
a controlled transmission line past the AD8178 inputs and termi-
nate the end of the line. This is known as fly-by termination.
The input impedance of the AD8178 is large enough, and stub
length inside the package is small enough, that this works well
in practice. Implementation of fly-by input termination often
includes bringing the signal in on one routing layer, then passing
through a filled via under the AD8178 input ball, then back out
to termination on another signal layer. In this case, care must be
taken to tie the reference ground planes together near the signal
via if the signal layers are referenced to different ground planes.
Rev. 0 | Page 36 of 40
V
n
f
P
PEAK
1
2
+
=
(11)
When driving the AD8178 single-endedly, the undriven input is
often terminated with a resistance to balance the input stage.
By terminating the undriven input with a resistor of one-half
the characteristic impedance, the input stage is perfectly
balanced (25 Ω, for example, to balance the two parallel 50 Ω
terminations on the driven input). However, due to the
feedback in the input receiver, there is high speed signal current
leaving the undriven input. To terminate this high speed signal,
proper transmission line techniques should be used. One
solution is to adjust the trace width to create a transmission line
of half the characteristic impedance and terminate the far end
with this resistance (25 Ω in a 50 Ω system). This is not often
practical because trace widths become large. In most cases, the
best practical solution is to place the half-characteristic impedance
resistor as close as possible (preferably less than 1.5 cm away)
and reduce the parasitics of the stub (by removing the ground
plane under the stub, for example). In either case, the designer
must decide if the layout complexity created by a balanced,
terminated solution is preferable to simply grounding the
undriven input at the ball with no trace.
While the examples discussed so far are for input termination,
the theory is similar for output back-termination. Taking the
AD8178 as an ideal voltage source, any distance of routing between
the AD8178 and a back-termination resistor is an impedance
mismatch that potentially creates reflections. For this reason,
back-termination resistors should also be placed close to the
AD8178. In practice, because back-termination resistors are
series elements, they can be placed close to the AD8178
outputs.
Finally, the AD8178 pinout allows the user to bring the outputs
out as surface traces to the back-termination resistors. The
designer can avoid creating stubs and reflections by keeping the
AD8178 output signal path on the surface of the board. A stub
is created when a top-to-bottom via connection is made on the
output signal path that is perpendicular to the signal flow.
AD8178
OPn
ONn
IPn
INn
50
0
Figure 52. Fly-By Input Termination. (Grounds for the two transmission lines
shown must be tied together close to the INn pin.)
If multiple AD8178s are to be driven in parallel, a fly-by input
termination scheme is very useful, but the distance from each
AD8178 input to the driven input transmission line is a stub
that should be minimized in length and parasitics by using the
discussed guidelines.
相關PDF資料 |
PDF描述 |
|---|---|
| AD8178ABPZ1 | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8178ABPZ | 功能描述:IC VIDEO CROSSPOINT SWIT 676BGA RoHS:是 類別:集成電路 (IC) >> 接口 - 模擬開關，多路復用器，多路分解器 系列:- 其它有關文件:STG4159 View All Specifications 標準包裝:5,000 系列:- 功能:開關 電路:1 x SPDT 導通狀態電阻:300 毫歐 電壓電源:雙電源 電壓 - 電源，單路/雙路(±):±1.65 V ~ 4.8 V 電流 - 電源:50nA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:7-WFBGA，FCBGA 供應商設備封裝:7-覆晶 包裝:帶卷 (TR) |
| AD8178ABPZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178-EVALZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD817AN | 功能描述:IC OPAMP HS LP 8-DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 放大器 - 視頻放大器和頻緩沖器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 應用:TFT-LCD 面板：VCOM 驅動器 輸出類型:滿擺幅 電路數:1 -3db帶寬:35MHz 轉換速率:40 V/µs 電流 - 電源:3.7mA 電流 - 輸出 / 通道:1.3A 電壓 - 電源，單路/雙路(±):9 V ~ 20 V，±4.5 V ~ 10 V 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬）裸露焊盤 供應商設備封裝:8-uMax-EP 包裝:管件 |
| AD817AN | 制造商:Analog Devices 功能描述:SEMICONDUCTORSLINEAR |
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