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參數資料
| 型號： | AD8178 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| 中文描述： | 450兆赫，三16】5視頻交叉點開關 |
| 文件頁數： | 33/40頁 |
| 文件大小： | 545K |
| 代理商： | AD8178 |
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AD8178
Rev. 0 | Page 33 of 40
QNPN
QPNP
V
NEG
V
POS
V
OUTPUT
I
OUTPUT
I
O, QUIESCENT
I
O, QUIESCENT
0
Figure 51. Simplified Output Stage
Example
With an ambient temperature of 85°C, all nine RGB output
channels driving 1 V
rms
into 100 Ω loads, and power supplies at
±2.5 V, follow these steps:
1.
Calculate the power dissipation of the AD8178 using data
sheet quiescent currents, neglecting the V
DD
current because
it is insignificant.
P
D,QUIESCENT
= (
V
POS
×
I
VPOS
) + (
V
NEG
×
I
VNEG
)
(4)
P
D,QUIESCENT
= (2.5 V × 460 mA) + (2.5 V × 460 mA) = 2.3 W
2.
Calculate power dissipation from loads. For a differential
output and ground-referenced load, the output power is
symmetrical in each output phase.
P
D,OUTPUT
= (
V
POS
V
OUTPUT,RMS
) ×
I
OUTPUT,RMS
(5)
P
D,OUTPUT
= (2.5 V 1 V) × (1 V/100 Ω) = 15 mW
There are 15 output pairs, or 30 output currents.
nP
D,OUTPUT
= 30 × 15 mW = 0.45 W
Subtract quiescent output stage current for the number of
loads (30 in this example). The output stage is either standing
or driving a load, but the current needs to be counted only
once (valid for output voltages > 0.5 V).
P
DQ,OUTPUT
= (
V
POS
V
NEG
) ×
I
OUTPUT,QUIESCENT
3.
(6)
P
DQ,OUTPUT
= (2.5 V (2.5 V)) × 1.65 mA = 8.25 mW
There are 15 output pairs, or 30 output currents.
nP
D,OUTPUT
= 30 × 8.25 mW = 0.25 W
4.
Verify that the power dissipation does not exceed the
maximum allowed value.
P
D,ON-CHIP
=
P
D,QUIESCENT
+
nP
D,OUTPUT
nP
DQ,OUTPUT
(7)
P
D,ON-CHIP
= 2.3 W + 0.45 W 0.25 W = 2.5 W
From Figure 50 or Equation 1, this power dissipation is below
the maximum allowed dissipation for all ambient temperatures
up to and including 85°C.
In a general case, the power delivered by the digital supply and
dissipated into the digital output devices has to be taken into
account following a similar derivation. However, because the
loads driven by the H and V outputs are high and because the
voltage at these outputs typically sits close to either rail, the
correction to the on-chip power estimate is small. Furthermore,
the H and V outputs are active only briefly during sync
generation and returned to digital ground thereafter.
Short-Circuit Output Conditions
Although there is short-circuit current protection on the AD8178
outputs, the output current can reach values of 80 mA into
a grounded output. Any sustained operation with too many
shorted outputs can exceed the maximum die temperature
and can result in device failure (see the Absolute Maximum
Ratings section).
Crosstalk
Many systems (such as KVM switches) that handle numerous
analog signal channels have strict requirements for keeping the
various signals from influencing any of the other signals 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 is undoubtedly the case in a system that uses the AD8178,
the crosstalk issues can be quite complex. A good understanding
of the nature of crosstalk and some definition of terms is required
to specify a system that uses one or more crosspoint devices.
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 the
sharing of common impedances. This section explains 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 propagates
across a stray capacitance (for example, free space) and couples
with the receiver and induces a voltage. This voltage is an unwanted
crosstalk signal in any channel that receives it.
Currents flowing in conductors create magnetic fields that circulate
around the currents. These magnetic fields then generate 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
channels. 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 common
impedance.
All these sources of crosstalk are vector quantities, so the magni-
tudes 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 AD8178 is a fully differential design means that
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8178ABPZ | 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) |
| AD8178ABPZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD8178-EVALZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:450 MHz, Triple 16 】 5 Video Crosspoint Switch |
| AD817AN | 功能描述:IC OPAMP HS LP 8-DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 放大器 - 視頻放大器和頻緩沖器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:50 系列:- 應用:TFT-LCD 面板：VCOM 驅動器 輸出類型:滿擺幅 電路數:1 -3db帶寬:35MHz 轉換速率:40 V/µs 電流 - 電源:3.7mA 電流 - 輸出 / 通道:1.3A 電壓 - 電源，單路/雙路(±):9 V ~ 20 V，±4.5 V ~ 10 V 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬）裸露焊盤 供應商設備封裝:8-uMax-EP 包裝:管件 |
| AD817AN | 制造商:Analog Devices 功能描述:SEMICONDUCTORSLINEAR |
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