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PDF AD8124 Data sheet ( Hoja de datos )
| Número de pieza | AD8124 | |
| Descripción | Triple Differential Receiver | |
| Fabricantes | Analog Devices | |
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Data Sheet
Triple Differential Receiver with
200 Meter Adjustable Cable Equalization
AD8124
FEATURES
Compensates cables to 200 meters for wideband video
All resolutions through UXGA
Fast rise and fall times
8 ns with 2 V step at 200 meters of UTP cable
37 dB peak gain at 100 MHz
Two frequency response gain adjustment pins
High frequency peaking adjustment (VPEAK)
Broadband flat gain adjustment (VGAIN)
Pole location adjustment pin (VPOLE)
Compensates for variations between cables
Can be optimized for either UTP or coaxial cable
DC output offset adjust (VOFFSET)
Low output offset voltage: 24 mV
Compensates both RGB and YPbPr
Two on-chip comparators with hysteresis
Can be used for common-mode sync extraction
Available in 40-lead, 6 mm × 6 mm LFCSP
APPLICATIONS
Keyboard-video-mouse (KVM)
Digital signage
RGB video over UTP cables
Professional video projection and distribution
HD video
Security video
GENERAL DESCRIPTION
The AD8124 is a triple, high speed, differential receiver and
equalizer that compensates for the transmission losses of UTP
and coaxial cables up to 200 meters in length. Various gain stages
are summed together to best approximate the inverse frequency
response of the cable. Logic circuitry inside the AD8124 controls
the gain functions of the individual stages so that the lowest
noise can be achieved at short-to-medium cable lengths. This
technique optimizes its performance for low noise, short-to-
medium range applications, while at the same time provides
the high gain bandwidth required for longer cable equalization
(up to 200 meters). Each channel features a high impedance
differential input that is ideal for interfacing directly with the cable.
FUNCTIONAL BLOCK DIAGRAM
VPEAK VPOLE VOFFSET VGAIN
AD8124
–INR
+INR
–ING
+ING
–INB
+INB
–INCMP1
+INCMP1
–INCMP2
+INCMP2
Figure 1.
OUTR
OUTG
OUTB
OUTCMP1
OUTCMP2
The AD8124 has three control pins for optimal cable
compensation, as well as an output offset adjust pin. Two
voltage-controlled pins are used to compensate for different
cable lengths; the VPEAK pin controls the amount of high frequency
peaking and the VGAIN pin adjusts the broadband flat gain, which
compensates for the low frequency flat cable loss.
For added flexibility, an optional pole adjustment pin, VPOLE,
allows movement of the pole locations, allowing for the
compensation of different gauges and types of cable as well
as variations between different cables and/or equalizers. The
VOFFSET pin allows the dc voltage at the output to be adjusted,
adding flexibility for dc-coupled systems.
The AD8124 is available in a 6 mm × 6 mm, 40-lead LFCSP
and is rated to operate over the extended temperature range of
−40°C to +85°C.
Rev. A
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2011–2015 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD8124
Parameter
COMPARATORS
Output Voltage Levels
Hysteresis
Propagation Delay
Rise/Fall Times
Output Resistance
OPERATING TEMPERATURE RANGE
Test Conditions/Comments
VOH/VOL
VHYST
tPD, LH/tPD, HL
tRISE/tFALL
Data Sheet
Min Typ
3.33/0.043
70
17.5/10.0
9.3/9.3
0.03
−40
Max Unit
V
mV
ns
ns
Ω
+85 °C
Rev. A | Page 4 of 15
5 Page 
AD8124
THEORY OF OPERATION
The AD8124 is a unity-gain, triple, wideband, low noise analog
line equalizer that compensates for losses in UTP and coaxial
cables up to 200 meters in length. The 3-channel architecture
is targeted at high resolution RGB applications but can be used
in HD YPbPr applications as well.
Three continuously adjustable control voltages, common
to the RGB channels, are available to the designer to provide
compensation for various cable lengths as well as for variations
in the cable itself. The VPEAK input is used to control the amount
of high frequency peaking. VPEAK is the primary control that is
used to compensate for frequency and cable-length dependent,
high frequency losses that are present due to the skin effect of
the cable. A second control pin, VGAIN, is used to adjust broadband
gain to compensate for low frequency flat losses present in the
cable. A third control, VPOLE, is used to move the positions of the
equalizer poles and can be linearly derived from VPEAK, as illustrated
in the Typical Performance Characteristics section and
Applications Information section, for UTP and coaxial cables.
Finally, an output offset adjust control, VOFFSET, allows the designer
to shift the output dc level.
The AD8124 has a high impedance differential input that makes
termination simple and allows dc-coupled signals to be received
directly from the cable. The AD8124 input can also be used in a
single-ended fashion in coaxial cable applications.
The AD8124 has a low impedance output that is capable of driving
a 150 Ω load. For systems where the AD8124 has to drive a high
impedance capacitive load, it is recommended that a small series
resistor be placed between the output and load to buffer the
capacitance. The resistor should not be so large as to reduce
the overall bandwidth to an unacceptable level.
Data Sheet
The AD8124 is designed such that systems that use short-to-
medium-length cables do not pay a noise penalty for excess gain
that they do not require. The high gain is only available for
longer length systems where it is required. This feature is built
into the VPEAK control and is transparent to the user.
Two comparators are provided on-chip that can be used for sync
pulse extraction in systems that use sync-on-common mode
encoding. Each comparator has very low output impedance and
can therefore be used in a source-only cable termination scheme
by placing a series resistor equal to the cable characteristic impedance
directly on the comparator output. Additional details are provided
in the Applications Information section.
INPUT COMMON-MODE VOLTAGE RANGE
CONSIDERATIONS
When using the AD8124 as a receiver, it is important to ensure
that its input common-mode voltage stays within the specified
range. The received common-mode level is calculated by adding
the common-mode level of the driver, the single-ended peak
amplitude of the received signal, the amplitude of any sync
pulses, and the other induced common-mode signals, such as
ground shifts between the driver and the AD8124 and pickup
from external sources, such as power lines and fluorescent lights.
See the Applications Information section for more details.
Rev. A | Page 10 of 15
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AD8124.PDF ] | |
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