參數資料
| 型號： | AD8176ABPZ |
| 廠商： | Analog Devices Inc |
| 文件頁數： | 29/40頁 |
| 文件大小： | 0K |
| 描述： | IC VIDEO CROSSPOINT SWIT 676BGA |
| 標準包裝： | 1 |
| 功能： | 視頻交叉點開關 |
| 電路： | 3 x 16:9 |
| 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： | 600mA |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 676-BGA |
| 供應商設備封裝： | 676-BGA（27x27） |
| 包裝： | 管件 |
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AD8176
Rev. 0 | Page 35 of 40
The flexible programming capability of the AD8176 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 OUTPUT4 (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 OUTPUT4 disabled. Because grounded
INPUT7 is programmed to drive OUTPUT4, 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 (OUTPUT4 in the middle) are programmed to
connect to INPUT0. OUTPUT4 is programmed to connect to
INPUT15 (far away from INPUT0), which is terminated to
ground. Thus, OUTPUT4 should not have a signal present
because it is listening to a quiet input. Any signal measured at
the OUTPUT4 can be attributed to the output crosstalk of the
other eight 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
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 termi-
nation 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
]
(10)
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.
From Equation 10, 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 AD8176 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
AD8176.
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
(11)
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.
The packaging of the AD8176 is designed to help keep the
crosstalk to a minimum. On the BGA 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.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8176-EVAL | 制造商:AD 制造商全稱:Analog Devices 功能描述:475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8177 | 制造商:AD 制造商全稱: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 類別:集成電路 (IC) >> 接口 - 模擬開關，多路復用器，多路分解器 系列:- 其它有關文件:STG4159 View All Specifications 標準包裝:5,000 系列:- 功能:開關 電路:1 x SPDT 導通狀態(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，FCBGA 供應商設備封裝:7-覆晶 包裝:帶卷 (TR) |
| 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 |
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