参数资料
| 型号： | AD8176ABPZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 28/40页 |
| 文件大小： | 0K |
| 描述： | IC VIDEO CROSSPOINT SWIT 676BGA |
| 标准包装： | 1 |
| 功能： | 视频交叉点开关 |
| 电路： | 3 x 16:9 |
| 电压电源： | 单/双电源 |
| 电压 - 电源，单路/双路(±)： | 4.5 V ~ 5.5 V，±2.5V |
| 电流 - 电源： | 600mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 676-BGA |
| 供应商设备封装： | 676-BGA（27x27） |
| 包装： | 管件 |
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AD8176
Rev. 0 | Page 34 of 40
becomes an input crosstalk signal for other channels that share
the common 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. The fact that the AD8176 is a fully-differential
design means that many sources of crosstalk either destructively
cancel, or are common-mode to the signal and can be rejected
by a differential receiver.
Areas of Crosstalk
A practical AD8176 circuit must be mounted to an actual
circuit board in order to connect it to power supplies and
measurement equipment. Great care has been taken to create an
evaluation board (available upon request) that adds minimum
crosstalk to the intrinsic device. This, however, raises the issue
that a system’s crosstalk is a combination of the intrinsic crosstalk
of the devices in addition to the circuit board to which they are
mounted. It is important to try to separate these two areas when
attempting to minimize the effect of crosstalk.
In addition, crosstalk can occur among the inputs to a crosspoint
and among the outputs. It can also occur from input to output.
In the following sections, techniques are 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
channels and measuring the relative strength of that signal on a
desired selected channel. The measurement is usually expressed
as decibels down from the magnitude of the test signal. The
crosstalk is expressed by
=
)
(
)
(
log
20
10
s
A
s
A
XT
TEST
SEL
(9)
where:
s is the Laplace transform variable (s = jω).
ASEL(s) is the amplitude of the crosstalk induced signal in the
selected channel.
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 has a phase relative to the test
signal associated with it.
A network analyzer is most commonly used to measure
crosstalk over a frequency range of interest. It can provide both
magnitude and phase information about the crosstalk signal.
As a crosspoint system or device grows larger, the number
of theoretical crosstalk combinations and permutations can
become extremely large. For example, in the case of the triple
16 × 9 matrix of the AD8176, look at the number of crosstalk
terms that can be considered for a single channel, say input
channel INPUT0. INPUT0 is programmed to connect to one of
the AD8176 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
can 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 measure-
ment) are taken into consideration, the numbers rather quickly
grow to astronomical proportions. If a larger crosspoint array of
multiple AD8176s 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
AD8176, 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 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.
相关PDF资料 |
PDF描述 |
|---|---|
| AD8177ABPZ | IC VIDEO CROSSPOINT SWIT 676BGA |
| AD8178ABPZ | IC VIDEO CROSSPOINT SWIT 676BGA |
| AD8182ANZ | IC MULTIPLEXER DUAL 2X1 14DIP |
| AD8184AR | IC VIDEO MULTIPLEXER 4X1 14SOIC |
| AD8185ARUZ | IC MULTIPLEXER TRPL 2X1 24TSSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8176-EVAL | 制造商:AD 制造商全称:Analog Devices 功能描述:475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8177 | 制造商:AD 制造商全称: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 类别:集成电路 (IC) >> 接口 - 模拟开关，多路复用器，多路分解器 系列:- 其它有关文件:STG4159 View All Specifications 标准包装:5,000 系列:- 功能:开关 电路:1 x SPDT 导通状态电阻:300 毫欧 电压电源:双电源 电压 - 电源，单路/双路(±):±1.65 V ~ 4.8 V 电流 - 电源:50nA 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:7-WFBGA，FCBGA 供应商设备封装:7-覆晶 包装:带卷 (TR) |
| AD8177-EVALZ | 制造商:AD 制造商全称:Analog Devices 功能描述:500 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178 | 制造商:AD 制造商全称:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
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