National Semiconductor Application Note 2002 Gary Melchior September 22, 2009 Introduction 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. 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 TABLE 1. CLC014 and LMH0074 Key Differences Power Supply (VCC) CLC014 LMH0074 5.0V 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 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. Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 AN-2002 © 2009 National Semiconductor Corporation 301059 www.national.com AN-2002 30105901 FIGURE 1. CLC014 Typical Application 30105902 FIGURE 2. LMH0074 Typical Application 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. INPUT INTERFACE For the typical input interface, the equalizer receives a singleended 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). www.national.com 2 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. 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. 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. 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. 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 30105903 FIGURE 3. CLC014 Differential Twisted Pair Input Interface 30105904 FIGURE 4. LMH0074 Differential Twisted Pair Input Interface as the ability to bypass equalization. The LMH0074’s smaller, space-saving 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. 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 3 www.national.com AN-2002 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. Replacing the CLC014 Adaptive Cable Equalizer with the LMH0074 Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Solutions www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS. EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness. National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. AN-2002 Copyright© 2009 National Semiconductor Corporation For the most current product information visit us at www.national.com National Semiconductor Americas Technical Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Technical Support Center Email: [email protected] National Semiconductor Asia Pacific Technical Support Center Email: [email protected] National Semiconductor Japan Technical Support Center Email: [email protected]