參數(shù)資料
型號(hào)： AD8115
廠商： Analog Devices, Inc.
英文描述： Low Cost 225 MHz 16 X 16 Crosspoint Switches
中文描述： 低成本的225 MHz 16 × 16交叉點(diǎn)開關(guān)
文件頁(yè)數(shù)： 18/26頁(yè)
文件大?。?/td> 363K
代理商： AD8115
AD8114/AD8115
–18–
REV. 0
Since S-video also uses two separate circuits for one video chan-
nel, creating a crosspoint system requires assigning one video
channel to two crosspoint channels as in the case of a differen-
tial video system. Aside from the nature of the video format,
other aspects of these two systems will be the same.
There are yet other video formats using three channels to carry
the video information. Video cameras produce RGB (red, green,
blue) directly from the image sensors. RGB is also the usual
format used by computers internally for graphics. RGB can also
be converted to Y, R-Y, B-Y format, sometimes called YUV
format. These three-circuit, video standards are referred to as
component analog video.
The component video standards require three crosspoint chan-
nels per video channel to handle the switching function. In a
fashion similar to the two-circuit video formats, the inputs and
outputs are assigned in groups of three and the appropriate logic
programming is performed to route the video signals.
CROSSTALK
Many systems, such as broadcast video, that handle numerous
analog signal channels have strict requirements for keeping the
various signals from influencing any of the others in the system.
Crosstalk is the term used to describe the coupling of the signals
of other nearby channels to a given channel.
When there are many signals in close proximity in a system, as
will undoubtedly be the case in a system that uses the AD8114/
AD8115, the crosstalk issues can be quite complex. A good
understanding of the nature of crosstalk and some definition of
terms is required in order to specify a system that uses one or
more AD8114/AD8115s.
Types of Crosstalk
Crosstalk can be propagated by means of any of three methods.
These fall into the categories of electric field, magnetic field and
sharing of common impedances. This section will explain these
effects.
Every conductor can be both a radiator of electric fields and a
receiver of electric fields. The electric field crosstalk mechanism
occurs when the electric field created by the transmitter propa-
gates across a stray capacitance (e.g., free space) and couples
with the receiver and induces a voltage. This voltage is an un-
wanted crosstalk signal in any channel that receives it.
Currents flowing in conductors create magnetic fields that circu-
late around the currents. These magnetic fields will then gener-
ate voltages in any other conductors whose paths they link. The
undesired induced voltages in these other channels are crosstalk
signals. The channels that crosstalk can be said to have a mutual
inductance that couples signals from one channel to another.
The power supplies, grounds and other signal return paths of a
multichannel system are generally shared by the various chan-
nels. When a current from one channel flows in one of these
paths, a voltage that is developed across the impedance becomes
an input crosstalk signal for other channels that share the com-
mon impedance.
All these sources of crosstalk are vector quantities, so the
magnitudes cannot simply be added together to obtain the total
crosstalk. In fact, there are conditions where driving additional
circuits in parallel in a given configuration can actually reduce
the crosstalk.
Areas of Crosstalk
For a practical AD8114/AD8115 circuit, it is required that it be
mounted to some sort of circuit board in order to connect it to
power supplies and measurement equipment. Great care has
been taken to create a characterization board (also available as
an evaluation board) that adds minimum crosstalk to the intrin-
sic device. This, however, raises the issue that a system’s crosstalk
is a combination of the intrinsic crosstalk of the devices in addi-
tion to the circuit board to which they are mounted. It is impor-
tant to try to separate these two areas of crosstalk when attempting
to minimize its effect.
In addition, crosstalk can occur among the inputs to a cross-
point and among the output. It can also occur from input to
output. Techniques will be discussed for diagnosing which part
of a system is contributing to crosstalk.
Measuring Crosstalk
Crosstalk is measured by applying a signal to one or more chan-
nels and measuring the relative strength of that signal on a de-
sired selected channel. The measurement is usually expressed as
dB down from the magnitude of the test signal. The crosstalk is
expressed by:
|
XT
| = 20 log
10
(
Asel
(
s
)/
Atest
(
s
))
where
s
=
jw
is the Laplace transform variable,
Asel
(
s
) is the
amplitude of the crosstalk-induced signal in the selected channel
and
Atest
(
s
) is the amplitude of the test signal. It can be seen
that crosstalk is a function of frequency, but not a function of
the magnitude of the test signal (to first order). In addition, the
crosstalk signal will have a phase relative to the test signal asso-
ciated with it.
A network analyzer is most commonly used to measure crosstalk
over a frequency range of interest. It can provide both magni-
tude and phase information about the crosstalk signal.
As a crosspoint system or device grows larger, the number of
theoretical crosstalk combinations and permutations can be-
come extremely large. For example, in the case of the 16
×
16
matrix of the AD8114/AD8115, we can examine the number of
crosstalk terms that can be considered for a single channel, say
IN00 input. IN00 is programmed to connect to one of the
AD8114/AD8115 outputs where the measurement can be made.
First, we can measure the crosstalk terms associated with driv-
ing a test signal into each of the other 15 inputs one at a time,
while applying no signal to IN00. We can then measure the
crosstalk terms associated with driving a parallel test signal into
all 15 other inputs taken two at a time in all possible combina-
tions; and then three at a time, etc., until, finally, there is only
one way to drive a test signal into all 15 other inputs 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 to specify them. In addition, this describes
the crosstalk matrix for just one input channel. A similar cross-
talk matrix can be proposed for every other input. In addition, if
the possible combinations and permutations for connecting
inputs to the other (not used for measurement) outputs are
taken into consideration, the numbers rather quickly grow to
astronomical proportions. If a larger crosspoint array of multiple
AD8114/AD8115s 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
相關(guān)PDF資料
PDF描述
AD8115* No RSENSE Current Mode Synchronous Step-Down Switching Regulator; Package: SO; No of Pins: 16; Temperature Range: 0°C to +70°C
AD8116 Buffered Video Crosspoint Switch(200MHz,視頻正交開關(guān))
AD8117_07 600 MHz, 32 】 32 Buffered Analog Crosspoint Switch
AD8117ABPZ 600 MHz, 32 】 32 Buffered Analog Crosspoint Switch
AD8117-EVAL 600 MHz, 32 】 32 Buffered Analog Crosspoint Switch
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD8115AST 制造商:Analog Devices 功能描述:Analog Video Crosspoint 200MHz 16 x 16 100-Pin LQFP 制造商:Rochester Electronics LLC 功能描述:TQFP 300MHZ 16X16 G=+2 CROSSPOINT SWITCH - Tape and Reel 制造商:Analog Devices 功能描述:IC SWITCH CROSSPOINT
AD8115ASTZ 功能描述:IC VIDEO CROSSPOINT SWIT 100LQFP 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:- 特色產(chǎn)品:MicroPak? 標(biāo)準(zhǔn)包裝:1 系列:- 功能:開關(guān) 電路:2 x SPST - NC 導(dǎo)通狀態(tài)電阻:500 毫歐 電壓電源:單電源 電壓 - 電源，單路/雙路(±):1.4 V ~ 4.3 V 電流 - 電源:150nA 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-XFDFN 供應(yīng)商設(shè)備封裝:8-XSON，SOT833-1 （1.95x1） 包裝:Digi-Reel® 其它名稱:568-5557-6
AD8115ASTZ 制造商:Analog Devices 功能描述:IC SWITCH VIDEO
AD8115ASTZ2 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost 225 MHz 16 ?? 16 Crosspoint Switches
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