Texas Instruments | Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 (Rev. A) | Application notes | Texas Instruments Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 (Rev. A) Application notes

Texas Instruments Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 (Rev. A) Application notes
Application Report
SNLA123A – September 2009 – Revised April 2013
AN-2002 Replacing the CLC014 Adaptive Cable Equalizer
with the LMH0074
.....................................................................................................................................................
ABSTRACT
This application report discusses the process to replace the CLC014 adaptive cable equalizer with the
LMH0074 adaptive cable equalizer.
1
2
3
Contents
Introduction ..................................................................................................................
How To Replace the CLC014 with the LMH0074 ......................................................................
2.1
Input Interface ......................................................................................................
2.2
Output Interface ....................................................................................................
2.3
AEC Capacitor Value ..............................................................................................
2.4
Carrier Detect and Mute ..........................................................................................
2.5
Other Features .....................................................................................................
2.6
100Ω DIfferential Twisted Pair Cable Applications ............................................................
LMH0074 Enhancements over the CLC014 .............................................................................
2
2
4
4
4
4
4
4
5
List of Figures
1
CLC014 Typical Application ............................................................................................... 3
2
LMH0074 Typical Application
4
.............................................................................................
CLC014 Differential Twisted Pair Input Interface .......................................................................
LMH0074 Differential Twisted Pair Input Interface .....................................................................
1
CLC014 and LMH0074 Key Differences ................................................................................. 2
3
3
5
5
List of Tables
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SNLA123A – September 2009 – Revised April 2013
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AN-2002 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074
Copyright © 2009–2013, Texas Instruments Incorporated
1
Introduction
1
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Introduction
The LMH0074 SD-SDI adaptive cable equalizer can replace the CLC014 adaptive cable equalizer in many
applications. The LMH0074 and CLC014 are both adaptive cable equalizers designed to recover data sent
over long cables, primarily for the SMPTE 259M interface. The supported data rates and cable lengths are
similar between the two devices. The LMH0074 and CLC014 are both rated for industrial temperature
range operation (-40°C to +85°C).
The LMH0074, the newer generation SDI equalizer, has more advanced features and is pin compatible
with the LMH0044 HD-SDI equalizer and the LMH0344 or LMH0384 3G-SDI equalizer. This allows a
forward migration path from SD to HD to 3G. The LMH0074 also offers a lower supply voltage (3.3V),
enabling system designers to migrate to lower-power designs. The LMH0074 provides a 28% power
savings over the CLC014, with typical power of 209 mW in comparison with 280 mW for the CLC014.
Table 1 shows the key differences between the CLC014 and LMH0074.
Table 1. CLC014 and LMH0074 Key Differences
CLC014
Power Supply (VCC)
3.3V
14-pin SOIC
16-pin LLP
Data Rates
50 to 650 Mbps
125 to 540 Mbps
ESD Rating
≥±500V HBM
≥±8 kV HBM
Input Interface
Requires 100Ω series resistor on
each input
Requires return loss network of 6.8
nH in parallel with 75Ω on active
input
Output Structure
Open collector, requires external
75Ω pullups to 5V
CML with internal 50Ω pullups (to
3.3V)
Package
AEC Capacitor Value
Carrier Detect / Mute Polarity
Other Features
2
LMH0074
5.0V
100 pF
1.0 µF
CD, MUTE
CD, MUTE
OEM
MUTEREF, BYPASS
How To Replace the CLC014 with the LMH0074
Replacing the CLC014 with the LMH0074 requires a few simple steps. The device packages and pinouts
are quite different so this change requires a new PCB layout; however, the equalizer core and features are
similar. To replace the CLC014 with the LMH0074, follow these steps:
1. Change the power supply from 5V to 3.3V.
2. Remove the 100Ω series resistors at the input to the equalizer.
3. Add an input return loss network consisting of a 6.8 nH inductor in parallel with a 75Ω resistor on the
active input between the BNC and the 75Ω termination.
4. Removed the 75Ω pullups on the output and replace with a 100Ω differential termination located at the
input of the next stage. The outputs may also be AC coupled, but no pullups are required.
5. Replace the 100 pF AEC capacitor with a 1.0 µF AEC capacitor.
Figure 1 shows the typical application for the CLC014, and Figure 2 shows the typical application for the
LMH0074.
2
AN-2002 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074
SNLA123A – September 2009 – Revised April 2013
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How To Replace the CLC014 with the LMH0074
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VCC
75:
Coaxial Cable
1 PF
75:
CLC014
75:
100:
DI
DO
DI
DO
Outputs
100:
75:
1 PF
CD
MUTE
37.4:
AEC+
AEC-
OEM
100 pF
CD
MUTE
OEM
Figure 1. CLC014 Typical Application
6.8 nH
Coaxial Cable
1 PF
LMH0074
SDI
SDO
SDI
SDO
4.7 PF
75:
Outputs
75:
4.7 PF
1 PF
CD
MUTE
37.4:
MUTEREF
AEC+
BYPASS
AEC-
1 PF
CD
MUTE
MUTEREF
BYPASS
Figure 2. LMH0074 Typical Application
SNLA123A – September 2009 – Revised April 2013
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AN-2002 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074
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3
How To Replace the CLC014 with the LMH0074
2.1
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Input Interface
For the typical input interface, the equalizer receives a single-ended signal over 75Ω coaxial cable. The
CLC014 requires a 75Ω termination to ground, a 1.0 µF input coupling capacitor, and a 100Ω series
resistor on each input. On the unused input, the 75Ω termination to ground is replaced by 37.4Ω to match
the impedance on the active side (which has the 75Ω cable in parallel with the 75Ω termination).
The 100Ω series resistors are not required for the LMH0074; however, a 6.8 nH inductor in parallel with a
75Ω resistor should be added in series on the active input between the input BNC and the 75Ω pulldown
resistor (see Figure 2). This network provides excellent input return loss. All of these components should
be placed close to the LMH0074 input pins.
2.2
Output Interface
The CLC014 outputs are open collector and require 75Ω pullups to 5V to generate an output voltage. This
structure has some limitations when interfacing to non-5V systems. The CLC014 outputs are essentially
cut off if the DO output voltage drops below VCC-1.6V (typically 3.4V), so this prevents DC-coupling to
other 3.3V devices.
The LMH0074 provides much more flexibility. The LMH0074 outputs are CML with internal 50Ω pullups to
3.3V. They may be DC coupled to many more types of inputs, including the LMH0026 or LMH0036
reclocker and the LMH0001 cable driver. Typically only a far-end differential termination (a simple resistor)
is required. If the LMH0074 output common mode voltage is not compatible with the input common mode
voltage of the receiving device, the outputs may be AC coupled as shown in Figure 2. The outputs do not
require pullups to VCC.
2.3
AEC Capacitor Value
The CLC014 AEC capacitor is typically 100 pF and may be changed to change the adaptive loop time
constant. For the LMH0074, the AEC capacitor should be 1.0 µF only. The LMH0074 was designed and
optimized for a 1.0 µF AEC capacitor and it should not be changed.
2.4
Carrier Detect and Mute
In CLC014 applications, the carrier detect pin (CD) is typically tied to the MUTE pin to inhibit the output
when there is no input signal. For the LMH0074 this can be done as well. The only difference is that the
polarity of the carrier detect and mute is reversed for the LMH0074; the carrier detect pin, CD , is active
low, and the mute pin, MUTE, is active high.
2.5
Other Features
The CLC014 has an Output Eye Monitor which shows the equalized eye pattern prior to the output
comparator. This feature is not included in the LMH0074; however, the LMH0074 includes features in
addition to those in CLC014, such as the MUTEREF and BYPASS functions. MUTEREF sets the threshold for
CD and (with CD tied to MUTE) determines the amount of cable to equalize before muting the outputs.
This may be useful to limit the maximum cable length that can be equalized, or for very noisy
environments where CD would need to be less sensitive. BYPASS passes the input signal through to the
output with no equalization. This may be useful for very low data rate applications.
2.6
100Ω DIfferential Twisted Pair Cable Applications
The equalizers can both be used for differential twisted pair cable applications. Figure 3 shows the
differential twisted pair input interface for the CLC014 and Figure 4 shows the differential twisted pair input
interface for the LMH0074.
4
AN-2002 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074
SNLA123A – September 2009 – Revised April 2013
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LMH0074 Enhancements over the CLC014
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1 PF
24.9:
100:
DI
Differential
Twisted Pair
24.9:
CLC014
24.9:
DI
24.9:
1 PF
100:
Figure 3. CLC014 Differential Twisted Pair Input Interface
1 PF
SDI
Differential
Twisted Pair
LMH0074
100:
SDI
1 PF
Figure 4. LMH0074 Differential Twisted Pair Input Interface
3
LMH0074 Enhancements over the CLC014
The LMH0074 is a solid upgrade and good replacement for the CLC014. It is designed in a newer, more
advanced process. The LMH0074 offers lower power, better ESD protection, a more flexible output
interface, and new features such as the ability to bypass equalization. The LMH0074’s smaller, spacesaving package allows for more compact designs. The PCB layout is simpler as the LMH0074 requires
less PCB components overall than the CLC014. In addition, the LMH0074’s pin compatibility with HD-SDI
and 3G-SDI equalizers offers an easy upgrade path and allows future-proof designs.
SNLA123A – September 2009 – Revised April 2013
Submit Documentation Feedback
AN-2002 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074
Copyright © 2009–2013, Texas Instruments Incorporated
5
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