NATIONAL SEMICONDUCTOR LMH6739 Very Wideband Low Distortion Triple Video Buffer Manual
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1. 1 10 100 1000 FREQUENCY MHz 20104133 Disabled Channel Isolation vs Frequency LK dBc 30 2 20104141 www national com 66 9 UNITY GAIN COMPENSATION With a current feedback Selectable Gain Buffer like the LMH6739 the feedback resistor is a compromise between the value needed for stability at unity gain and the optimized value used at a gain of two The result of this compromise is substantial peaking at unity gain If this peaking is undesirable a simple RC filter at the input of the buffer will smooth the frequency response shown as Figure 4 Figure 5 shows the results of a simple filter placed on the non inverting input See Figure 6 and Figure 7 for another method for reducing unity gain peaking 20104107 FIGURE 6 Alternate Unity Gain Compensation GAIN dB 1 10 100 1000 FREQUENCY MHz 20104137 FIGURE 7 Frequency Response for Circuit in Figure 6 x1 Rout 510 RIN 510 RL 1 kO 20104138 FIGURE 8 Decoupling Capacitive Loads DRIVING CAPACITIVE LOADS Capacitive output loading applications will benefit from the use of a series output resistor Rou Figure 8 shows the use of a series output resistor Rour to stabilize the amplifier out put under capacitive loading Capacitive loads of 5 to 120 pF2. TER SEATING PLANE MQA46 Rev B 11 www national com 66 9 LMH6739 Very Wideband Low Distortion Triple Video Buffer Notes For more National Semiconductor product information and proven design tools visit the following Web sites at LVDS www national com Ivds Reference Designs www national com refdesigns Power Management www national com power Feedback www national com feedback wireless PLLVCO 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 SHOUL
3. December 10 2007 National Semiconductor LMH6739 Very Wideband Low Distortion Triple Video Buffer General Description Features The LMH67339 is a very wideband DC coupled monolithic se 750 MHz 3 dB small signal bandwidth Ay 1 lectable gain buffer designed specifically for ultra high reso 85 dBc 3 harmonic distortion 20 MHz lution video systems as well as wide dynamic range systems 2 3nVNHz input noise voltage requiring exceptional signal fidelity Benefiting from National s current feedback architecture the LMH6739 offers gains of 3300 s slew rate 1 1 and 2 At a gain of 2 the LMH6739 supports ultra high 32 mA supply current 10 6 mA per op amp resolution video systems with a 400 MHz 2 Vpp 90 mA linear output current 3 dB Bandwidth With 12 bit distortion level through 30 MHz 0 02 0 01 Diff Gain Diff Phase R RL 2 3nV Hz input referred noise the LMH6739 is the ideal driver or buffer for high speed flash A D and D A ETA SAMONA GUMENE converters Wide dynamic range systems such as radar and i communication receivers requiring a wideband amplifier of Applications fering exceptional signal purity will find the LMH6739 s low RGB video driver input referred noise and low harmonic distortion make it an attractive solution The LMH6739 is offered in a space saving N SSOP package Flash A D driver D A transimpedance buffer Wide dynamic range IF amp Radar communication receivers DDS post amps Wideba
4. are the most critical causing ringing frequency response peaking and possible oscillation The charts Suggested vs Cap Load give a recommended value for selecting a series output resistor for mitigating capacitive loads The values suggested in the charts are selected for 5 dB or less of peaking in the frequency response This gives a good com promise between settling time and bandwidth For applica tions where maximum frequency response is needed and some peaking is tolerable the value of Roy be reduced slightly from the recommended values LAYOUT CONSIDERATIONS Whenever questions about layout arise use the evaluation board as a guide The LMH730275 is the evaluation board supplied with samples of the LMH6739 To reduce parasitic capacitances ground and power planes should be removed near the input and output pins Compo nents in the feedback loop should be placed as close to the device as possible For long signal paths controlled impedance lines should be used along with impedance matching elements at both ends Bypass capacitors should be placed as close to the device as possible Bypass capacitors from each rail to ground are ap plied in pairs The larger electrolytic bypass capacitors can be located farther from the device the smaller ceramic capaci tors should be placed as close to the device as possible The LMH6739 has multiple power and ground pins for enhanced supply bypassing Every pin should i
5. 00 FREQUENCY MHz 20104135 BQ Frequency Response vs Capacitive Load 120 DISTORTION dBc 4 7 pF Rg 700 DANN F Rg 440 RN 1 10 100 1000 FREQUENCY MHz 20104114 Open Loop Gain and Phase 20104126 10 MHz HD vs Output Level OUTPUT VOLTAGE 20104134 www national com 66 9 CMRR vs Frequency 10 8 11 6 12 4 10 TOTAL SUPPLY VOLTAGE V 9 2 Distortion vs Supply Voltage 68 76 84 29 NOILYOLSIG 6 Z9HIN1 FREQUENCY MHz 20104111 20104118 Closed Loop Output Impedance 121 PSRR vs Frequency 0 1 FREQUENCY MHz 0 001 0 01 20104104 20104121 DC Errors vs Temperature Disable Timing INIYYNO SVIS AW 1 13S44O A A LNdLNO TEMPERATURE C TIME ns 20104112 20104124 www national com CROSSTALK dBc Crosstalk vs Frequency amp C VouT 2 MEASURE
6. D 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 Switching Regulators www national com switchers 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
7. Frequency Domain Performance 2 Sommet Tw ease DisebieTine From Deae tainge 4 Eves Non verdig e _ EE EE 8 Differential Phase 443 MHz R _ _ 4 5 21 5 40 www national com 2 Note 7 Note 6 Note 7 Power Supply Rejection Ratio Note 50 53 Common Mode Rejection Ratio F U l 46 5 Note 8 44 Mode Input Range Note CMRR gt 40 dB 1 9 2 0 8 1 7 Linear Output Current Notes 4 8 Vin OV lt 30 80 60 Short Circuit Current Note 9 Vin 2V Output ShortedtoGround 160 Dmv Gegen e _ Note 1 Absolute Maximum Ratings indicate limits beyond which damage to the device may occur Operating Ratings indicate conditions for which the device is intended to be functional but specific performance is not guaranteed For guaranteed specifications see the Electrical Characteristics tables Note 2 Electrical Table values apply only for factory testing conditions at the temperature indicated Factory testing conditions result in very limited self heating of the device such that T T No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self heating where T gt T See Applications Informati
8. brand or product names may be trademarks or registered trademarks of their respective holders Copyright 2007 National Semiconductor Corporation For the most current product information visit us at www national com National Semiconductor National Semiconductor Europe National Semiconductor Asia National Semiconductor Japan Americas Customer Customer Support Center Pacific Customer Support Center Customer Support Center Support Center Fax 49 0 180 530 85 86 Email ap support nsc com Fax 81 3 5639 7507 Email Email europe support nsc com Email jpn feedback nsc com new feedback nsc com Deutsch Tel 49 0 69 9508 6208 Tel 81 3 5639 7560 Tel 1 800 272 9959 English Tel 49 0 870 24 0 2171 Francais Tel 33 0 1 41 91 8790 www national com
9. deally have a separate bypass capacitor Sharing bypass capacitors may slightly de grade second order harmonic performance especially if the supply traces are thin and or long In Figure 1 and Figure 2 Css is optional but is recommended for best second harmon ic distortion Another option to using Css is to use pairs of OI Fand 1 F ceramic capacitors for each supply bypass VIDEO PERFORMANCE The LMH6739 has been designed to provide excellent per formance with production quality video signals in a wide va riety of formats such as HDTV and High Resolution VGA NTSC and PAL performance is nearly flawless Best perfor mance will be obtained with back terminated loads The back termination reduces reflections from the transmission line and effectively masks transmission line and other parasitic ca pacitances from the amplifier output stage Figure 4 shows a typical configuration for drivinga75 Cable The amplifier is configured for a gain of two to make up for the 6 dB of loss in Rout www national com 66 9 LMH6739 225 LFPM FORCED AIR MAXIMUM POWER DISSIPATION W 40 20 0 20 40 60 80 100 TEMPERATURE C 20104102 FIGURE 9 Maximum Power Dissipation POWER DISSIPATION The LMH6739 is optimized for maximum speed and perfor mance in the small form factor of the standard SSOP 16 package To achieve its high level of performance the LMH6739 consumes an appreciable a
10. e major heat flow path in this package is from the die through the metal lead frame inside the package and onto the sur rounding copper through the interconnecting leads Since high frequency performance requires limited metal near the device pins the best way to use board copper to remove heat is through the bottom of the package A gap filler with high thermal conductivity can be used to conduct heat from the bottom of the package to copper on the circuit board Vias to a ground or power plane on the back side of the circuit board will provide additional heat dissipation A combination of front side copper and vias to the back side can be combined as well Follow these steps to determine the maximum power dissi pation for the LMH6739 1 Calculate the quiescent no load power Pamp ec Vs Vg Vt V 2 Calculate the RMS power dissipated in the output stage Pp rms rms Vg Voyt lour where Vour and lour are the voltage and current across the external load and Vs is the total supply current 3 Calculate the total RMS power P Payp Pp The maximum power that the LMH6739 package can dissi pate at a given temperature can be derived with the following equation See Figure 9 150 ya Where Tame Ambient temperature C and ja Thermal resistance from junction to ambient for a given package C W For the SSOP package is 120 C W ESD PROTECTION The LMH6739 is protected against e
11. lectrostatic discharge ESD all pins The LMH6739 will survive 2000V Human Body model and 200V Machine model events Under closed loop operation the ESD diodes have no effect on circuit performance There are occasions however when the ESD diodes will be evident If the LMH6739 is driven by a large signal while the device is powered down the ESD diodes will conduct The current that flows through the ESD diodes will either exit the chip through the supply pins or will flow through the de vice hence it is possible to power up a chip with a large signal applied to the input pins Shorting the power pins to each other will prevent the chip from being powered up through the input www national com 10 Physical Dimensions inches millimeters unless otherwise noted PIN 1 236 1 008 10 063 005 004 NOT INCLUDING MOLD FLASH 193 004 006 PER END 16 010 002 ukasa 007M lt 016 MURUME 9 B 2157 2150 NOT INCLUDING MOLD FLASH RE 8 0045 0025 TYP 4 22 14 025 COMMENDED LAND PATTERN feo GAGE PLANE 057 010 a 16X on 0 8 DIMENSIONS ARE IN INCHES DIMENSIONS IN FOR REFERENCE ONLY 16 Pin SSOP NS Package Number MQA16 r 2025 005
12. lication Information for more details 3 www national com 66 9 LMH6739 Typical Performance Characteristics 2 5 GAIN dB NORMALIZED GAIN dB NORMALIZED GAIN dB Large Signal Frequency Response 1 10 100 1000 FREQUENCY MHz 20104131 Frequency Response vs Vour 10 100 1000 FREQUENCY MHz 20104101 Gain Flatness Vour 0 5 20104139 Small Signal Frequency Response NORMALIZED GAIN dB 1 10 100 1000 FREQUENCY MHz 20104132 Frequency Response vs Supply Voltage NORMALIZED GAIN dB 10 100 1000 FREQUENCY MHz 20104116 Gain Flatness Dual Input Buffer GAIN dB 1 10 100 1000 FREQUENCY MHz 20104140 www national com unless otherwise specified Series Output Resistance vs Capacitive Load RECOMMENDED R DISTORTION dBc Pulse Response 1 5 7 0 5 0 5 1 1 5 0 4 8 12 16 20 TIME ns 20104122 80 70 0 20 40 60 80 100 120 CAPACITIVE LOAD pF 20104119 Distortion vs Frequency 1 10 1
13. mount of quiescent current which cannot be neglected when considering the total package power dissipation limit The quiescent current con tributes to about 40 C rise in junction temperature when no additional heat sink is used Vs 5V all channels Therefore it is easy to see the need for proper precautions to be taken in order to make sure the junction temperature s ab solute maximum rating of 150 C is not violated To ensure maximum output drive and highest performance thermal shutdown is not provided Therefore it is of utmost importance to make sure that the is never exceeded due to the overall power dissipation all 3 channels With the LMH6739 used in a back terminated 75 RGB ana log video system with 2 Vpp output voltage the total power dissipation is around 435 mW of which 340 mW is due to the quiescent device dissipation output black level at 0V With no additional heat sink used that puts the junction tempera ture to about 140 C when operated at 85 C ambient To reduce the junction temperature many options are avail able Forced air cooling is the easiest option An external add on heat sink can be added to the SSOP 16 package or alternatively additional board metal copper area can be uti lized as heat sink An effective way to reduce the junction temperature for the SSOP 16 package and other plastic packages is to use the copper board area to conduct heat With no enhancement th
14. nd inverting summer Line driver High resolution projectors Connection Diagram 16 Pin SSOP 20104110 Top View Ordering Information Number Package Marking Media NSC Drawing 16 Pin SSOP LMH6739MQ 95 95 Units Rail LH6739MQ MQA16 LMH6739MQX 2 5k Units Tape and Reel VIP10 is a trademark of National Semiconductor Corporation 2007 National Semiconductor Corporation 201041 www national com 1 6EZ9HINT LMH6739 Absolute Maximum Ratings Note 1 Soldering Intormation 3 Infrared or Convection 20 sec 235 C If Military Aerospace specified devices are required 260 please contact the National Semiconductor Sales Office Wave Soldering 10 sec 60 Distributors for availability and specifications Storage Temperature Range 65 C to 150 ESD Tolerance Note 3 2000 Operating Ratings Note 1 Machine Model 200V Temperature Range Note 5 40 C to 85 C Supply Voltage V V 13 2V Supply Voltage V V 8V to 12V lout Note 4 Thermal Resistance Common Mode Input Voltage Package uc Maximum Junction Temperature 150 C 16 Pin SSOP 36 C W 120 C W Storage Temperature Range 65 C to 150 C Electrical Characteristics Note 2 Ty 25 C Ay 2 5 RL unless otherwise specified Note 7 Note 6 Note 7
15. on for information on temperature de rating of this device Min Max ratings are based on product characterization and simulation Individual parameters are tested as noted Note 3 Human Body Model applicable std MIL STD 883 Method 3015 7 Machine Model applicable std JESD22 A115 A ESD MM std of JEDEC Field Induced Charge Device Model applicable std JESD22 C101 C ESD FICDM std of JEDEC Note 4 The maximum output current is determined by device power dissipation limitations See the Power Dissipation section of the Application Information for more details Note 5 The maximum power dissipation is a function of Tymax maximum allowable power dissipation at any ambient temperature is Pp Timax Ta Ja All numbers apply for packages soldered directly onto a PC Board Note 6 Typical values represent the most likely parametric norm as determined at the time of characterization Actual typical values may vary over time and will also depend on the application and configuration The typical values are not tested and are not guaranteed on shipped production material Note 7 Limits are 100 production tested at 25 C Limits over the operating temperature range are guaranteed through correlations using the Statistical Quality Control SQC method Note 8 Parameter 100 production tested at 25 C Note 9 Short circuit current should be limited in duration to no more than 10 seconds See the Power Dissipation section of the App
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NATIONAL SEMICONDUCTOR LMH6739 Very Wideband Low Distortion Triple Video Buffer Manual