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參數資料
| 型號： | AD8148ACPZ-R7 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Triple Differential Driver for Wideband Video |
| 中文描述： | 三差分驅動器的寬帶視頻 |
| 文件頁數： | 15/24頁 |
| 文件大小： | 438K |
| 代理商： | AD8148ACPZ-R7 |
AD8146/AD8147/AD8148
CALCULATING THE INPUT IMPEDANCE
The effective input impedance of a circuit such as that in
Figure 28 at V
IP
and V
IN
depends on whether the amplifier is
being driven by a single-ended or differential signal source. For
balanced differential input signals, the differential input impedance,
R
IN, dm
, between the inputs V
IP
and V
IN
for all devices is
R
IN, dm
= 2 ×
R
G
In the case of a single-ended input signal (for example, if V
IN
is
grounded and the input signal is applied to V
IP
), the input
impedance becomes
Rev. 0 | Page 15 of 24
OUTPUT COMMON-MODE CONTROL
The AD8146 allows the user to control each of the three
common-mode output levels independently through the three
V
OCM
input pins. The V
OCM
pins pass a signal to the common-
mode output level of each of their respective amplifiers with
330 MHz of small signal bandwidth and an internally fixed gain
of 1. In this way, additional control and communication signals
can be embedded on the common-mode levels as users see fit.
With no external circuitry, the level at the V
OCM
input of each
amplifier defaults to approximately midsupply. An internal
resistive divider with an impedance of approximately 12.5 kΩ
sets this level. To limit common-mode noise in dc common-
mode applications, external bypass capacitors should be
connected from each of the V
OCM
input pins to ground.
SYNC-ON COMMON-MODE
The AD8147 and AD8148 are specifically targeted at driving
RGB video signals over UTP cable using a sync-on common-
mode technique. The common-mode outputs of each of the R,
G, and B differential outputs are set using circuitry contained
within the device. This circuitry embeds the horizontal and
vertical sync pulses on the three common-mode outputs in a
way that also results in low radiated energy. For a more detailed
description of the sync scheme, see the Applications section.
The sync-on common-mode circuit generates a current based
on the SYNC LEVEL input pin (Pin 18). With the SYNC LEVEL
input tied to GND, the common-mode output of all drivers is
set at (V
S+
+ V
S
)/2. Using a resistor divider, a voltage can be
applied between GND and SYNC LEVEL that determines the
maximum deviation of the common-mode outputs from their
midsupply level. If, for instance, SYNC LEVEL = 0.5 V and the
supply voltage is 5 V, the common-mode outputs fall within an
envelope of 2.5 V ± 0.5 V The state of each V
OUT, cm
output based
on the H
SYNC
and V
SYNC
inputs is determined by the equations
defined in the Applications section.
In most cases, the sync-on common-mode circuit can be used
by directly applying the H
SYNC
and V
SYNC
signals to their respective
AD8147 or AD8148 inputs. The logic thresholds of the H
SYNC
and V
SYNC
inputs are set to nominally 1.4 V with respect to
GND, and the exposed paddles of the AD8147 and AD8148
are used as the GND references for the incoming sync pulses.
When ±2.5 V supplies are used, however, external protection is
required to limit the positive excursion to less than 2.5 V. For
more details, see the Applications section.
The input paths from the H
SYNC
and V
SYNC
inputs to the switches
in the current mode level-shifting circuit are well matched to
eliminate false switching transients, maximizing common-
mode balance and minimizing radiated energy.
(
)
+
×
=
F
G
F
G
R
dm
IN,
R
R
R
R
2
1
The single-ended input impedance of the AD8146 and the
AD8147 is therefore 750 Ω, and the single-ended input
impedance of the AD8148 is 833 Ω.
The input impedance of the circuit is effectively higher than it
would be for a conventional op amp connected as an inverter
because a fraction of the differential output voltage appears at
the inputs as a common-mode signal, partially bootstrapping
the voltage across the input resistor R
G
.
INPUT COMMON-MODE VOLTAGE RANGE IN
SINGLE-SUPPLY APPLICATIONS
The driver inputs are designed to facilitate level-shifting of
ground-referenced input signals on a single power supply. For a
single-ended input, this implies, for example, that the voltage at
V
IN
in Figure 28 would be 0 V when the negative power supply
voltage of the amplifier is also set to 0 V.
It is important to ensure that the common-mode voltage at the
amplifier inputs, V
AP
and V
AN
, stays within its specified range.
Because voltages V
AP
and V
AN
are driven to be essentially equal
by negative feedback, the input common-mode voltage of the
amplifier can be expressed as a single term, V
ACM
. V
ACM
can be
calculated as
2
ICM
OCM
ACM
V
=
3
V
V
+
where V
ICM
is the common-mode voltage of the input signal,
that is,
V
ICM
= (
V
IP
+
V
IN
)
/2.
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| AD8148ACPZ-RL | 功能描述:IC DRIVER TRIPLE DIFF 24-LFCSP RoHS:是 類別:集成電路 (IC) >> 線性 - 放大器 - 視頻放大器和頻緩沖器 系列:- 標準包裝:1,000 系列:- 應用:驅動器 輸出類型:差分 電路數:3 -3db帶寬:350MHz 轉換速率:1000 V/µs 電流 - 電源:14.5mA 電流 - 輸出 / 通道:60mA 電壓 - 電源，單路/雙路(±):5 V ~ 12 V，±2.5 V ~ 6 V 安裝類型:表面貼裝 封裝/外殼:20-VFQFN 裸露焊盤 供應商設備封裝:20-QFN 裸露焊盤（4x4） 包裝:帶卷 (TR) |
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| AD8150AST | 制造商:Rochester Electronics LLC 功能描述:LQFP 1.5GBPS 33X17 DIGITAL CROSSPOINT SW - Tape and Reel 制造商:Analog Devices 功能描述:IC SWITCH CROSSPOINT |
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