參數(shù)資料
型號(hào)： AD8177ABPZ
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 29/40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(kāi)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 35 of 40
For example, in the case of the triple 16 × 5 matrix of the AD8177,
we can look at the number of crosstalk terms that can be
considered for a single channel, such as Input Channel INPUT0.
INPUT0 is programmed to connect to one of the AD8177
outputs where the measurement can be made.
First, the crosstalk terms associated with driving a test signal into
each of the other 15 input channels can be measured one at a
time, while applying no signal to INPUT0. Then, the crosstalk
terms associated with driving a parallel test signal into all 15 other
inputs can be measured two at a time in all possible combinations,
then three at a time, and so on, until, finally, there is only one
way to drive a test signal into all 15 other input channels in
parallel.
Each of these cases is legitimately different from the others and
might yield a unique value, depending on the resolution of the
measurement system; but it is hardly practical to measure all
these terms and then specify them. In addition, this describes
the crosstalk matrix for just one input channel. A similar crosstalk
matrix can be proposed for every other input. In addition, if the
possible combinations and permutations for connecting inputs
to the other outputs (not used for measurement) are taken into
consideration, the numbers rather quickly grow to astronomical
proportions. If a larger crosspoint array of multiple AD8177s is
constructed, the numbers grow larger still.
Obviously, some subset of all these cases must be selected to be
used as a guide for a practical measure of crosstalk. One common
method is to measure all hostile crosstalk; this means that the
crosstalk to the selected channel is measured while all other system
channels are driven in parallel. In general, this yields the worst
crosstalk number, but this is not always the case, due to the
vector nature of the crosstalk signal.
Other useful crosstalk measurements are those created by one
nearest neighbor or by the two nearest neighbors on either side.
These crosstalk measurements are generally higher than those
of more distant channels, so they can serve as a worst-case
measure for any other one-channel or two-channel crosstalk
measurements.
Input and Output Crosstalk
Capacitive coupling is voltage-driven (dV/dt) but is generally
a constant ratio. Capacitive crosstalk is proportional to input or
output voltage, but this ratio is not reduced by simply reducing
signal swings. Attenuation factors must be changed by changing
impedances (lowering mutual capacitance), or destructive
canceling must be utilized by summing equal and out-of-phase
components. For high input impedance devices such as the
AD8177, capacitances generally dominate input-generated
crosstalk.
Inductive coupling is proportional to current (dI/dt) and often
scales as a constant ratio with signal voltage, but it also shows
a dependence on impedances (load current). Inductive coupling
can also be reduced by constructive canceling of equal and out-
of-phase fields. In the case of driving low impedance video loads,
output inductances contribute highly to output crosstalk.
The flexible programming capability of the AD8177 can be used
to diagnose whether crosstalk is occurring more on the input
side or the output side. Some examples are illustrative. A given
input channel (INPUT7, roughly in the middle for this example)
can be programmed to drive OUTPUT2 (exactly in the middle).
The inputs to INPUT7 are just terminated to ground (via 50 Ω
or 75 Ω), and no signal is applied.
All the other inputs are driven in parallel with the same test signal
(practically provided by a distribution amplifier), with all other
outputs except OUTPUT2 disabled. Because grounded INPUT7
is programmed to drive OUTPUT2, no signal should be present.
Any signal that is present can be attributed to the other 15 hostile
input signals because no other outputs are driven (they are all
disabled). Thus, this method measures the all-hostile input
contribution to crosstalk into INPUT7. Of course, the method
can be used for other input channels and combinations of
hostile inputs.
For output crosstalk measurement, a single input channel is
driven (INPUT0, for example) and all outputs other than a given
output (OUTPUT2 in the middle) are programmed to connect
to INPUT0. OUTPUT2 is programmed to connect to INPUT15
(far away from INPUT0), which is terminated to ground. Thus,
OUTPUT2 should not have a signal present because it is listening
to a quiet input. Any signal measured at the OUTPUT2 can be
attributed to the output crosstalk of the other four hostile outputs.
Again, this method can be modified to measure other channels
and other crosspoint matrix combinations.
Effect of Impedances on Crosstalk
The input side crosstalk can be influenced by the output imped-
ance of the sources that drive the inputs. The lower the impedance
of the drive source, the lower the magnitude of the crosstalk.
The dominant crosstalk mechanism on the input side is capacitive
coupling. The high impedance inputs do not have significant
current flow to create magnetically induced crosstalk. However,
significant current can flow through the input termination
resistors and the loops that drive them. Thus, the PC board on
the input side can contribute to magnetically coupled crosstalk.
From a circuit standpoint, the input crosstalk mechanism looks
like a capacitor coupling to a resistive load. For low frequencies,
the magnitude of the crosstalk is given by
[
]s
C
R
XT
M
S
×
=
)
(
log
20
10
(9)
where:
RS
is the source resistance.
CM
is the mutual capacitance between the test signal circuit and
the selected circuit.
s
is the Laplace transform variable.
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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(kāi)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(kāi)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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