參數(shù)資料
型號(hào)： AD8108ASTZ
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 17/33頁(yè)
文件大?。?/td> 0K
描述： IC VIDEO CROSSPOINT SWIT 80LQFP
標(biāo)準(zhǔn)包裝： 1
功能： 視頻交叉點(diǎn)開關(guān)
電路： 1 x 8:8
電壓電源： 雙電源
電壓 - 電源，單路/雙路(±)： ±4.5 V ~ 5.5 V
電流 - 電源： 33mA
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 80-LQFP
供應(yīng)商設(shè)備封裝： 80-LQFP（12x12）
包裝： 托盤
AD8108/AD8109
Rev. B | Page 23 of 32
quickly grow to astronomical proportions. If a larger crosspoint
array of multiple AD8108/AD8109s is constructed, the numbers
grow larger still.
Effect of Impedances on Crosstalk
The input side crosstalk can be influenced by the output
impedance 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.
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 term
means that the crosstalk to the selected channel is measured
while all other system channels are driven in parallel. In general,
this will yield 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 will generally be higher than
those of more distant channels, so they can serve as a worst-case
measure for any other 1-channel or 2-channel crosstalk
measurements.
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 will be given by
(
)
[
]s
M
C
S
R
XT
×
=
10
log
20
Input and Output Crosstalk
where
RS is the source resistance, CM is the mutual capacitance
between the test signal circuit and the selected circuit, and
s is
the Laplace transform variable.
The flexible programming capability of the AD8108/AD8109
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 (IN03 in the middle for this example)
can be programmed to drive OUT03. The input to IN03 is just
terminated to ground (via 50 or 75 ) and no signal is
applied.
From the equation, it can be observed that this crosstalk
mechanism has a high-pass nature; it can 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 terminated cable, the input crosstalk can be
reduced by buffering this signal with a low output impedance
buffer.
All the other inputs are driven in parallel with the same test
signal (practically this is provided by a distribution amplifier),
with all other outputs except OUT03 disabled. Since grounded
IN03 is programmed to drive OUT03, there should be no signal
present. Any signal that is present can be attributed to the other
seven 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 IN03. Of course, the
method can be used for other input channels and combinations
of hostile inputs.
On the output side, the crosstalk can be reduced by driving a
lighter load. Although the AD8108/AD8109 is specified with
excellent differential gain and phase when driving a standard
150 video load, the crosstalk will be higher than the
minimum obtainable due to the high output currents. These
currents will induce crosstalk via the mutual inductance of the
output pins and bond wires of the AD8108/AD8109.
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
For output crosstalk measurement, a single input channel is
driven (IN00, for example) and all outputs other than a given
output (IN03 in the middle) are programmed to connect to
IN00. OUT03 is programmed to connect to IN07 (far away
from IN00), which is terminated to ground. Thus OUT03
should not have a signal present since it is listening to a quiet
input. Any signal measured at the OUT03 can be attributed to
the output crosstalk of the other seven hostile outputs. Again,
this method can be modified to measure other channels and
other crosspoint matrix combinations.
(
)
L
R
s
Mxy
XT
×
=
10
log
20
where
Mxy is the mutual inductance of Output x to Output y,
and
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.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD8108ASTZ 制造商:Analog Devices 功能描述:IC SWITCH VIDEO
AD8108ASTZ2 制造商:AD 制造商全稱:Analog Devices 功能描述:325 MHz, 8 ?? 8 Buffered Video Crosspoint Switches
AD8108EB 制造商:Analog Devices 功能描述:
AD8108-EB 制造商:Analog Devices 功能描述:Evaluation Board For IC Video Crosspt 325MHz 8X8 制造商:Analog Devices 功能描述:VID CROSSPT 325MHZ 8X8 - Bulk
AD8109 制造商:AD 制造商全稱:Analog Devices 功能描述:325 MHz, 8 x 8 Buffered Video Crosspoint Switches
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