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參數資料
| 型號： | AD8176-EVAL |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| 中文描述： | 475兆赫，三16】9視頻交叉點開關 |
| 文件頁數： | 31/32頁 |
| 文件大小： | 489K |
| 代理商： | AD8176-EVAL |
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Preliminary Technical Data
AD8176
AD8176 should be no more than 1.5 cm after the termination
resistors, and preferably should be placed even closer. The BGA
substrate routing inside the AD8176 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
AD8176 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 AD8176 inputs
and terminate the end of the line. This is known as fly-by
termination. The input impedance of the AD8176 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 AD8176 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. PrA | Page 31 of 32
V
n
f
P
PEAK
1
2
+
=
(11)
AD8176
OPn
ONn
IPn
INn
50
0
Figure 27. Fly-By Input Termination. (Grounds for the two transmission lines
shown must be tied together close to the INn pin.)
If multiple AD8176s are to be driven in parallel, a fly-by input
termination scheme is very useful, but the distance from each
AD8176 input to the driven input transmission line is a stub
that should be minimized in length and parasitics using the
discussed guidelines.
When driving the AD8176 single-endedly, the undriven input is
often terminated with a resistance in order to balance the input
stage. It can be seen that by terminating the undriven input with
a resistor of one-half the characteristic impedance, the input
stage will be 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. In order 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 as 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 to 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
AD8176 as an ideal voltage source, any distance of routing
between the AD8176 and a back-termination resistor will be a
stub that creates reflections. For this reason, back-termination
resistors should also be placed close to the AD8176. In practice,
because back-termination resistors are series elements, their
footprint in the routing is narrower and it is easier to place
them close in board layout.
Figure 28. Evaluation Board Schematic
相關PDF資料 |
PDF描述 |
|---|---|
| AD8176 | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8176ABPZ | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8178 | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178ABPZ1 | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178-EVALZ1 | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8177 | 制造商:AD 制造商全稱:Analog Devices 功能描述:500 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8177ABPZ | 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) |
| AD8177-EVALZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:500 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178 | 制造商:AD 制造商全稱:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| 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) |
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