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參數資料
| 型號： | AD8175ABPZ |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 運動控制電子 |
| 英文描述： | Video Crosspoint Switch |
| 中文描述： | 16-CHANNEL, CROSS POINT SWITCH, PBGA676 |
| 封裝： | 27 X 27 MM, 1 MM PITCH, ROHS COMPLIANT, PLASTIC, MS-034AAL-1, PBGA-676 |
| 文件頁數： | 31/40頁 |
| 文件大小： | 533K |
| 代理商： | AD8175ABPZ |
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AD8175
undriven input should be terminated with an impedance
matching that seen by the part at the driven input.
Differential Output
Benefits of Differential Operation
The AD8175 has a fully-differential switch core with differential
outputs. The two output voltages move in opposite directions,
with a differential feedback loop maintaining a fixed output
stage differential gain of +2. This differential output stage
provides improved crosstalk cancellation due to parasitic
coupling from one output to another being equal and out of
phase. Additionally, if the output of the device is utilized in a
differential design, then noise, crosstalk, and offset voltages
generated on-chip that are coupled equally into both outputs
are reduced by the common-mode rejection ratio of the next
device in the signal chain. By utilizing the AD8175 outputs in a
differential application, the best possible noise and offset
specifications can be realized.
Common-Mode Gain
The common-mode, or average voltage of pairs of output
signals, is set by the voltage on the VOCM_CMENCOFF pin
when common-mode encoding is off (CMENC is logic low), or
by the voltage on the VOCM_CMENCON pin when common-
mode encoding is on (CMENC is logic high). Note that in the
latter case, VCOM_CMENCON sets the overall common-mode
of RGB triplets of differential outputs, while the individual
common-mode of each RGB output is free to change. VCOM_
CMENCON and VCOM_CMENCOFF are typically set to
midsupply (often ground), but can be moved approximately
±0.5 V in order to accommodate cases where the desired output
common-mode voltage may not be midsupply (as in the case of
unequal split supplies). Adjusting the output common-mode
voltage beyond ±0.5 V can limit differential swing internally
below the specifications on the data sheet. The overall common-
mode of the output voltages follows the voltage applied to
VOCM_CMENCON or VCOM_CMENCOFF, implying a gain
of +1. Likewise, sync-on common-mode signaling is carried
through the AD8175 (CMENC must be in its high state),
implying a gain of +1 for this path as well.
The common-mode reference pins are analog signal inputs,
common to all output stages on the device. They require only
small amounts of bias current, but noise appearing on these
pins is buffered to all the output stages. As such, they should
be connected to low noise, low impedance voltage references
to avoid being sources of noise, offset, and crosstalk in the
signal path.
Termination
The AD8175 is designed to drive 100 Ω terminated to ground
on each output (or an effective 200 Ω differential) while
meeting data sheet specifications over the specified operating
temperature range, if care is taken to observe the maximum
power derating curves.
Rev. 0 | Page 31 of 40
Termination at the load end is recommended to shorten settling
time and for best signal integrity. In differential signal paths, it
is often desirable to series-terminate the outputs, with a resistor
in series with each output. A side effect of termination is an
attenuation of the output signal by a factor of two. In this case,
gain is usually necessary somewhere else in the signal path to
restore the signal level.
Whenever a differential output is used single-ended, it is
desirable to terminate the used single-ended output with a
series resistor, as well as to place a resistor on the unused output
to match the load seen by the used output.
When disabled, the outputs float to midsupply. A small current
is required to drive the outputs away from their midsupply
state. This current is easily provided by an AD8175 output (in
its enabled state) bussed together with the disabled output.
Exceeding the allowed output voltage range may saturate
internal nodes in the disabled output, and consequently an
increase in disabled output current may be observed.
Single-Ended Output
Usage
The AD8175 output pairs can be used single-ended, taking only
one output and not using the second. This is often desired to
reduce the routing complexity in the design, or because a
single-ended load is being driven directly. This mode of
operation produces good results, but has some shortcomings
when compared to taking the output differentially. When
observing the single-ended output, noise that is common to
both outputs appears in the output signal.
When observing the output single-ended, the distribution of
offset voltages will appear greater. In the differential case, the
difference between the outputs when the difference between the
inputs is zero is a small differential offset. This offset is created
from mismatches in devices in the signal path. In the single-
ended case, this differential offset is still observed, but an
additional offset component is also relevant. This additional
component is the common-mode offset, which is the difference
between the average of the outputs and the output common-
mode reference. This offset is created by mismatches that affect
the signal path in a common-mode manner. A differential
receiver rejects this common-mode offset voltage, but in the
single-ended case, this offset is observed with respect to the
signal ground. The single-ended output sums half the
differential offset voltage and all of the common-mode offset
voltage for a net increase in observed offset.
Single-Ended Gain
The AD8175 operates as a closed-loop differential amplifier.
The primary control loop forces the difference between the
output terminals to be a ratio of the difference between the
input terminals. One output increases in voltage, while the
other decreases an equal amount to make the total output
voltage difference correct. The average of these output voltages
相關PDF資料 |
PDF描述 |
|---|---|
| AD8175-EVALZ | Video Crosspoint Switch |
| AD8176-EVAL | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8176 | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8176ABPZ | 475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8178 | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8175-EVALZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:Video Crosspoint Switch |
| AD8176 | 制造商:AD 制造商全稱:Analog Devices 功能描述:475 MHz, Triple 16 】 9 Video Crosspoint Switch |
| AD8176ABPZ | 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) |
| 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 |
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