參數(shù)資料
型號(hào)： AD8177ABPZ
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 30/40頁(yè)
文件大?。?/td> 0K
描述： IC VIDEO CROSSPOINT SWIT 676BGA
標(biāo)準(zhǔn)包裝： 1
功能： 視頻交叉點(diǎn)開關(guān)
電路： 3 x 16:5
電壓電源： 單/雙電源
電壓 - 電源，單路/雙路(±)： 4.5 V ~ 5.5 V，±2.5V
電流 - 電源： 460mA
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 676-BGA
供應(yīng)商設(shè)備封裝： 676-BGA（27x27）
包裝： 管件
AD8177
Rev. 0 | Page 36 of 40
From Equation 9, it can be observed that this crosstalk mechanism
has a high-pass nature; it can also be minimized by reducing the
coupling capacitance of the input circuits and lowering the output
impedance of the drivers. If the input is driven from a 75 Ω
terminated cable, the input crosstalk can be reduced by buffering
this signal with a low output impedance buffer.
On the output side, the crosstalk can be reduced by driving
a lighter load. Although the AD8177 is specified with excellent
settling time when driving a properly terminated Cat-5, the
crosstalk is higher than the minimum obtainable, due to the high
output currents. These currents induce crosstalk via the mutual
inductance of the output pins and bond wires of the AD8177.
From a circuit standpoint, this output crosstalk mechanism looks
like a transformer with a mutual inductance between the windings
that drives a load resistor. For low frequencies, the magnitude of
the crosstalk is given by
×
=
L
XY
R
s
M
XT
10
log
20
(10)
where:
MXY
is the mutual inductance of Output X to Output Y.
RL
is the load resistance on the measured output.
This crosstalk mechanism can be minimized by keeping the
mutual inductance low and increasing RL. The mutual inductance
can be kept low by increasing the spacing of the conductors and
minimizing their parallel length.
PCB Layout
Extreme care must be exercised to minimize additional crosstalk
generated by the system circuit board(s). The areas that must
be carefully detailed are grounding, shielding, signal routing,
and supply bypassing.
Packaging of the AD8177 is designed to help keep crosstalk to
a minimum. On the PBGA substrate, each pair is carefully routed
to predominately couple to each other, with shielding traces
separating adjacent signal pairs. The ball grid array is arranged
such that similar board routing can be achieved. Input and output
differential pairs are grouped by channel rather than by color to
allow for easy, convenient board routing.
The input and output signals have minimum crosstalk if they
are located between ground planes on layers above and below
and separated by ground in between. Vias should be located as
close to the IC as possible to carry the inputs and outputs to the
inner layer. The input and output signals surface at the input
termination resistors and the output series back-termination
resistors. To the extent possible, these signals should also be
separated as soon as they emerge from the IC package.
PCB Termination Layout
As frequencies of operation increase, the importance of proper
transmission line signal routing becomes more important. The
bandwidth of the AD8177 is large enough that using high imped-
ance routing does not provide a flat in-band frequency response
for practical signal trace lengths. It is necessary for the user to
choose a characteristic impedance suitable for the application and
properly terminate the input and output signals of the AD8177.
Traditionally, video applications have used 75 Ω single-ended
environments. RF applications are generally 50 Ω single-ended
(and board manufacturers have the most experience with this
application). Cat-5 cabling is usually driven as differential pairs of
100 Ω differential impedance.
For flexibility, the AD8177 does not contain on-chip termina-
tion resistors. This flexibility in application comes with some
board layout challenges. The distance between the termination
of the input transmission line and the AD8177 die is a high
impedance stub and causes reflections of the input signal. With
some simplification, it can be shown that these reflections cause
peaking of the input at regular intervals in frequency, dependent
on the propagation speed (VP) of the signal in the chosen board
material and the distance (d) between the termination resistor
and the AD8177. 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 (VP = 144 × 106 m/s), this means
the AD8177 should be no more than 1.5 cm after the termination
resistors; preferably, it should be placed even closer. The BGA
substrate routing inside the AD8177 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
V
n
f
P
PEAK
4
1
2 +
=
(11)
where n = {0, 1, 2, 3, ...}.
In some cases, it is difficult to place the termination close to the
AD8177 due to space constraints, differential routing, and large
resistor footprints. A preferable solution in this case is to main-
tain a controlled transmission line past the AD8177 inputs and
terminate the end of the line. This is known as fly-by termination.
The input impedance of the AD8177 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 AD8177 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.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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(guān)，多路復(fù)用器，多路分解器 系列:- 其它有關(guān)文件:STG4159 View All Specifications 標(biāo)準(zhǔn)包裝:5,000 系列:- 功能:開關(guān) 電路:1 x SPDT 導(dǎo)通狀態(tài)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，F(xiàn)CBGA 供應(yīng)商設(shè)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
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