Texas Instruments | 3.3V Cable Driver And Equalizer Drive Mega-Bits @ Many Meters | Application notes | Texas Instruments 3.3V Cable Driver And Equalizer Drive Mega-Bits @ Many Meters Application notes

Texas Instruments 3.3V Cable Driver And Equalizer Drive Mega-Bits @ Many Meters Application notes
CLC001,CLC012,CLC016
3.3V Cable Driver And Equalizer Drive Mega-Bits @ Many Meters
Literature Number: SNLA151
106037_App.Brief#105_COM.qxd
7/17/01
2:06 PM
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Application Brief
3.3V Cable Driver And Equalizer Drive Mega-Bits @ Many Meters
Application Brief 105
Gary Melchior
The Cable Equalizer is the most important
element in serial digital interfaces.
Transmitting data over long distances is
necessary in a wide range of applications.
These include telecom and video electrical
interfaces running at data rates of up to
400 Mbps over appreciable distances. Long-haul
data transmission is easily accomplished with
existing devices. The new CLC001 cable
driver, CLC012 cable equalizer, and CLC016
data retiming PLL form a robust serial digital
interface that transmits megabits of data over
hundreds of meters. Figure 1 shows a typical
SDI application.
The cable equalizer has the task of recovering
the signal from a seemingly worthless waveform
[See Figure 2(b)] and restoring it to its proper
voltage levels. The CLC012 adaptive cable
equalizer does just that. It automatically
compensates for attenuation in cable
corresponding to up to 300 meters of
Belden 8281 coaxial cable or 120 meters of
Category 5 UTP. The CLC012 approximates
the reciprocal of the cable loss characteristic
and supplies 40 dB of gain at 200 MHz. Jitter
performance is 180 psp-p for 270 Mbps data
that has passed through 200 meters of Belden
8281 cable. A Loss of Signal output and an
output mute function are also provided.
Advertisement
The 3.3V Cable Driver
The CLC001 is a 3.3V cable driver ideal for
high-speed data transmission over long
distances. It drives 75Ω transmission lines
(Belden 8281 or equivalent) at data rates up
to 622 Mbps. Its versatile input stage allows
for a wide range of input levels, including
direct LVDS and LVPECL connections. Rise
and fall times are typically 400 ps. Its two
complementary outputs may be used singleended or differentially and are adjustable from
800 mVp-p to 1.0 Vp-p.
The Data Retimer cleans up jitter.
The CLC016 data retimer re-establishes proper
bit widths and their correct relationship to the
serial clock edges, in addition to extracting a
clock from the signal. Auto-rate select circuitry
allows the CLC016 to recognize up to four
data rates between 40 and 400 Mbps and
VCC
VCC
a
3.3V
1 µF
15.0Ω
75ΩCoax
75Ω
75Ω
75Ω
DI
DO
DDI
SDO
DI
DO
DDI
SDO
100Ω
1 µF
SDO
75Ω
1 µF 100Ω
75ΩCoax
SDO
60.4Ω
1 µF
75Ω
To
Additional
Channels
CLC001
c
b
EQ
RT
SCO
SCO
36.5Ω
CLC012
75Ω
75Ω
75Ω
Data
Outputs
Clock
Outputs
CLC016
Figure 1. Typical SDI Long-haul Application
*Note: (a), (b), and (c) represent the location of eye diagrams in Figure 2. This simplified schematic shows only the major signal path.
For more detailed schematics, please refer to the datasheets online at www.national.com/appinfo/interface
106037_App.Brief#105_COM.qxd
Ch1 200 mV
7/17/01
2:06 PM
M 1.00 ns Ch2 ƒ
500 mV
Page 2
Ch1 200 mV
(a) Driver Output
M 1.00 ns Ch2 ƒ
500 mV
Ch1 200 mV
(b) Equalizer Input
M 1.00 ns Ch2 ƒ
500 mV
(c) Retimer Output
Figure 2. Eye Diagrams at (a) Driver Output, (b) Equalizer Input, and (c) Retimer Output
automatically adjust to provide accurate,
low-jitter clock and data recovery. Output
jitter is only 130 psp-p at 270 Mbps.
The circuit in Figure 1 was tested at a data
rate of 311 Mbps. The signal source is a
PRBS pattern generated by a Tektronix
GigaBERT 700. The CLC001 drives 250
meters of Belden 8281 cable with a 1.0 Vp-p
output level. The signal at the CLC001
output is shown in Figure 2(a). After passing
through the cable, signal amplitude has fallen
to about 700 mV and the signal appears to
be worthless [Figure 2(b)].
A usable signal can be recovered by the
CLC012 after up to 300 meters of cable.
The signal is recovered and the data is
retimed by the CLC012 and CLC016,
respectively. The resultant signal is buffered
by another CLC001 to drive the line to the
scope and is shown in Figure 2(c).
As can be seen from these waveforms, the
CLC012 and CLC016 are very effective at
restoring data after hundreds of meters of
cable. SDI Interface devices can be used for
a wide variety of digital video, datacom, and
telecom applications.
Serial Digital Interface Selection Guide
Part Number
CLC001
CLC005
CLC006
CLC007
CLC012
CLC014
CLC016
CLC018
Description
3.3V Cable Driver with Adjustable Outputs
ITU Cable Driver with Adjustable Outputs
Cable Driver with Adjustable Outputs
Cable Driver with Dual Complementary Outputs
Adaptive Cable Equalizer (ITU)
Adaptive Cable Equalizer (SDV)
Data Retiming PLL with Auto Rate Selection
8X8 Digital Crosspoint Switch
National Semiconductor
2900 Semiconductor Dr.
PO Box 58090
Santa Clara, CA 95052
Jitter (ps)
25
25
25
25
180
180
130
50
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Data Rate
DC to 622 Mbps
DC to 400 Mbps
DC to 400 Mbps
DC to 400 Mbps
40 to 650 Mbps
40 to 650 Mbps
40 to 400 Mbps
DC to 1.485 Gbps
Data Sheet Download
http://www.national.com/pf/CL/CLC001.html
http://www.national.com/pf/CL/CLC012.html
http://www.national.com/pf/CL/CLC016.html
http://www.national.com/appinfo/interface
© National Semiconductor Corporation, 2001. National Semiconductor and
are registered trademarks of National Semiconductor Corporation. All rights reserved.
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