lm2675
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LM2675SIMPLE SWITCHER ®Power Converter High Efficiency 1A Step-Down Voltage RegulatorGeneral DescriptionThe LM2675series of regulators are monolithic integrated circuits built with a LMDMOS process.These regulators provide all the active functions for a step-down (buck)switching regulator,capable of driving a 1A load current with excellent line and load regulation.These devices are avail-able in fixed output voltages of 3.3V,5.0V,12V,and an adjustable output version.Requiring a minimum number of external components,these regulators are simple to use and include patented internal frequency compensation (Patent Nos.5,382,918and 5,514,947)and a fixed frequency oscillator.The LM2675series operates at a switching frequency of 260kHz,thus allowing smaller sized filter components than what would be needed with lower frequency switching regu-lators.Because of its very high efficiency (>90%),the cop-per traces on the printed circuit board are the only heat sinking needed.A family of standard inductors for use with the LM2675are available from several different manufacturers.This feature greatly simplifies the design of switch-mode power supplies using these advanced ICs.Also included in the datasheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies.Other features include a guaranteed ±1.5%tolerance on output voltage within specified input voltages and output load conditions,and ±10%on the oscillator frequency.Ex-ternal shutdown is included,featuring typically 50µA stand-by current.The output switch includes current limiting,as well as thermal shutdown for full protection under fault conditions.To simplify the LM2675buck regulator design procedure,there exists computer design software,LM267X Made Simple version 6.0.Featuresn Efficiency up to 96%n Available in SO-8,8-pin DIP and LLP packages n Computer Design Software LM267X Made Simple (version 6.0)n Simple and easy to design withn Requires only 5external components n Uses readily available standard inductorsn 3.3V,5.0V,12V,and adjustable output versionsn Adjustable version output voltage range:1.21V to 37V n ±1.5%max output voltage tolerance over line and load conditionsn Guaranteed 1A output load current n 0.25ΩDMOS Output Switchn Wide input voltage range:8V to 40Vn 260kHz fixed frequency internal oscillatorn TTL shutdown capability,low power standby mode n Thermal shutdown and current limit protectionTypical Applicationsn Simple High Efficiency (>90%)Step-Down (Buck)Regulatorn Efficient Pre-Regulator for Linear Regulators n Positive-to-Negative ConverterTypical Application01280301SIMPLE SWITCHER ®is a registered trademark of National Semiconductor Corporation.Windows ®is a registered trademark of Microsoft Corporation.June 2005LM2675SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator©2005National Semiconductor Corporation Connection Diagrams16-Lead LLP Surface Mount PackageTop View8-Lead PackageTop View01280338LLP PackageSee NSC Package Drawing Number LDA16A01280302SO-8/DIP PackageSee NSC Package Drawing Number MO8A/N08EPackage Marking and Ordering InformationTABLE 1.Output Voltage Order InformationPackage MarkingSupplied as:16Lead LLP12LM2675LD-12S000DB 1000Units on Tape and Reel 12LM2675LDX-12S000DB 4500Units on Tape and Reel 3.3LM2675LD-3.3S000EB 1000Units on Tape and Reel 3.3LM2675LDX-3.3S000EB 4500Units on Tape and Reel 5.0LM2675LD-5.0S000FB 1000Units on Tape and Reel 5.0LM2675LDX-5.0S000FB 4500Units on Tape and Reel ADJ LM2675LD-ADJ S000GB 1000Units on Tape and Reel ADJLM2675LDX-ADJS000GB4500Units on Tape and ReelSO-812LM2675M-122675M-12Shipped in Anti-Static Rails 12LM2675MX-122675M-122500Units on Tape and Reel 3.3LM2675M-3.32675M-3.3Shipped in Anti-Static Rails 3.3LM2675MX-3.32675M-3.32500Units on Tape and Reel 5.0LM2675M-5.02675M-5.0Shipped in Anti-Static Rails 5.0LM2675MX-5.02675M-5.02500Units on Tape and Reel ADJ LM2675M-ADJ 2675M-ADJ Shipped in Anti-Static Rails ADJLM2675MX-ADJ2675M-ADJ2500Units on Tape and ReelDIP12LM2675N-12LM2675N-12Shipped in Anti-Static Rails 3.3LM2675N-3.3LM2675N-3.3Shipped in Anti-Static Rails 5.0LM2675N-5.0LM2675N-5.0Shipped in Anti-Static Rails ADJLM2675N-ADJLM2675N-ADJShipped in Anti-Static RailsL M 2675 2Absolute Maximum Ratings(Note1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.Supply Voltage45V ON/OFF Pin Voltage−0.1V≤V SH≤6V Switch Voltage to Ground−1V Boost Pin Voltage V SW+8V Feedback Pin Voltage−0.3V≤V FB≤14V ESD SusceptibilityHuman Body Model(Note2)2kV Power Dissipation Internally Limited Storage Temperature Range−65˚C to+150˚C Lead TemperatureM PackageVapor Phase(60s)+215˚C Infrared(15s)+220˚C N Package(Soldering,10s)+260˚C LLP Package(See AN-1187)Maximum Junction Temperature+150˚COperating RatingsSupply Voltage 6.5V to40V Junction Temperature Range−40˚C≤T J≤+125˚C Electrical CharacteristicsLM2675-3.3Specifications with standard type face are for TJ=25˚C,and those with bold type face apply over full Operating Temperature Range.Symbol Parameter Conditions Typical Min Max Units(Note4)(Note5)(Note5) SYSTEM PARAMETERS Test Circuit Figure2(Note3)V OUT Output Voltage V IN=8V to40V,I LOAD=20mA to1A 3.3 3.251/3.201 3.350/3.399V V OUT Output Voltage V IN=6.5V to40V,I LOAD=20mA to500mA 3.3 3.251/3.201 3.350/3.399V ηEfficiency V IN=12V,I LOAD=1A86% LM2675-5.0Symbol Parameter Conditions Typical Min Max Units(Note4)(Note5)(Note5) SYSTEM PARAMETERS Test Circuit Figure2(Note3)V OUT Output Voltage V IN=8V to40V,I LOAD=20mA to1A 5.0 4.925/4.850 5.075/5.150V V OUT Output Voltage V IN=6.5V to40V,I LOAD=20mA to500mA 5.0 4.925/4.850 5.075/5.150V ηEfficiency V IN=12V,I LOAD=1A90% LM2675-12Symbol Parameter Conditions Typical Min Max Units(Note4)(Note5)(Note5) SYSTEM PARAMETERS Test Circuit Figure2(Note3)V OUT Output Voltage V IN=15V to40V,I LOAD=20mA to1A1211.82/11.6412.18/12.36V ηEfficiency V IN=24V,I LOAD=1A94% LM2675-ADJSymbol Parameter Conditions Typ Min Max Units(Note4)(Note5)(Note5) SYSTEM PARAMETERS Test Circuit Figure3(Note3)V FB FeedbackVoltage V IN=8V to40V,I LOAD=20mA to1AV OUT Programmed for5V(see Circuit of Figure3)1.210 1.192/1.174 1.228/1.246VV FB FeedbackVoltage V IN=6.5V to40V,I LOAD=20mA to500mAV OUT Programmed for5V(see Circuit of Figure3)1.210 1.192/1.174 1.228/1.246VLM26753LM2675-ADJ(Continued)Symbol Parameter ConditionsTyp Min Max Units(Note 4)(Note 5)(Note 5)ηEfficiencyV IN =12V,I LOAD =1A90%All Output Voltage VersionsSpecifications with standard type face are for T J =25˚C,and those with bold type face apply over full Operating Tempera-ture Range .Unless otherwise specified,V IN =12V for the 3.3V,5V,and Adjustable versions and V IN =24V for the 12V ver-sion,and I LOAD =100mA.Symbol ParametersConditionsTyp MinMax Units DEVICE PARAMETERSI QQuiescent CurrentV FEEDBACK =8V2.53.6mAFor 3.3V,5.0V,and ADJ Versions V FEEDBACK =15V 2.5mAFor 12V VersionsI STBY Standby Quiescent Current ON/OFF Pin =0V50100/150µA I CL Current Limit1.55 1.25/1.22.1/2.2A I LOutput Leakage CurrentV IN =40V,ON/OFF Pin =0V V SWITCH =0V125µA V SWITCH =−1V,ON/OFF Pin =0V615mA R DS(ON)Switch On-Resistance I SWITCH =1A0.250.30/0.50Ωf O Oscillator Frequency Measured at Switch Pin 260225275kHz D Maximum Duty Cycle 95%Minimum Duty Cycle 0%I BIAS Feedback Bias CurrentV FEEDBACK =1.3V ADJ Version Only 85nA V S/D ON/OFF PinVoltage Thesholds 1.40.8 2.0V I S/D ON/OFF Pin Current ON/OFF Pin =0V20737µA θJAThermal ResistanceN Package,Junction to Ambient (Note 6)95˚C/WM Package,Junction to Ambient (Note 6)105Note 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 device parameter specifications may not be guaranteed under these conditions.For guaranteed specifications and test conditions,see the Electrical Characteristics.Note 2:The human body model is a 100pF capacitor discharged through a 1.5k Ωresistor into each pin.Note 3:External components such as the catch diode,inductor,input and output capacitors,and voltage programming resistors can affect switching regulator performance.When the LM2675is used as shown in Figures 2,3test circuits,system performance will be as specified by the system parameters section of the Electrical Characteristics.Note 4:Typical numbers are at 25˚C and represent the most likely norm.Note 5:All limits guaranteed at room temperature (standard type face)and at temperature extremes (bold type face).All room temperature limits are 100%production tested.All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC)methods.All limits are used to calculate Average Outgoing Quality Level (AOQL).Note 6:Junction to ambient thermal resistance with approximately 1square inch of printed circuit board copper surrounding the leads.Additional copper area will lower thermal resistance further.See Application Information section in the application note accompanying this datasheet and the thermal model in LM267X Made Simple software (version 6.0).The value θJ−A for the LLP (LD)package is specifically dependent on PCB trace area,trace material,and the number of layers and thermal vias.For improved thermal resistance and power dissipation for the LLP package,refer to Application Note AN-1187.L M 2675 4Typical Performance CharacteristicsNormalizedOutput Voltage Line Regulation0128030301280304EfficiencyDrain-to-SourceResistance0128030501280306Switch Current LimitOperatingQuiescent Current0128030701280308LM26755Typical Performance Characteristics(Continued)StandbyQuiescent CurrentON/OFF ThresholdVoltage0128030901280310ON/OFF Pin Current (Sourcing)Switching Frequency0128031101280312Feedback Pin Bias CurrentPeak Switch Current0128031301280314L M 2675 6Typical Performance Characteristics(Continued)Dropout Voltage—3.3V Option Dropout Voltage—5.0V Option0128031501280316Block Diagram01280317*Active Inductor Patent Number5,514,947†Active Capacitor Patent Number5,382,918FIGURE1.LM26757Typical Performance Characteristics(Circuit of Figure 2)Continuous Mode Switching WaveformsV IN =20V,V OUT =5V,I LOAD =1AL =47µH,C OUT =68µF,C OUT ESR =50m ΩDiscontinuous Mode Switching Waveforms V IN =20V,V OUT =5V,I LOAD =300mAL =15µH,C OUT =68µF (2x),C OUT ESR =25m Ω01280318A:V SW Pin Voltage,10V/div.B:Inductor Current,0.5A/divC:Output Ripple Voltage,20mV/div AC-CoupledHorizontal Time Base:1µs/div01280319A:V SW Pin Voltage,10V/div.B:Inductor Current,0.5A/divC:Output Ripple Voltage,20mV/div AC-CoupledHorizontal Time Base:1µs/divLoad Transient Response for Continuous ModeV IN =20V,V OUT =5V,I LOAD =1AL =47µH,C OUT =68µF,C OUT ESR =50m ΩLoad Transient Response for Discontinuous ModeV IN =20V,V OUT =5V,L =47µH,C OUT =68µF,C OUT ESR =50m Ω01280320A:Output Voltage,100mV/div,AC-Coupled.B:Load Current:200mA to 1A Load PulseHorizontal Time Base:50µs/div 01280321A:Output Voltage,100mV/div,AC-Coupled.B:Load Current:100mA to 400mA Load PulseHorizontal Time Base:200µs/divL M 2675 8Test Circuit and Layout Guidelines01280322C IN -22µF,50V Tantalum,Sprague “199D Series”C OUT -47µF,25V Tantalum,Sprague “595D Series”D1-3.3A,50V Schottky Rectifier,IR 30WQ05F L1-68µH Sumida #RCR110D-680L C B -0.01µF,50V CeramicFIGURE 2.Standard Test Circuits and Layout GuidesFixed Output Voltage Versions01280323C IN -22µF,50V Tantalum,Sprague “199D Series”C OUT -47µF,25V Tantalum,Sprague “595D Series”D1-3.3A,50V Schottky Rectifier,IR 30WQ05F L1-68µH Sumida #RCR110D-680L R1-1.5k Ω,1%C B -0.01µF,50V CeramicFor a 5V output,select R2to be 4.75k Ω,1%where V REF =1.21VUse a 1%resistor for best stability.FIGURE 3.Standard Test Circuits and Layout GuidesAdjustable Output Voltage VersionLM26759LM2675Series Buck Regulator Design Procedure (Fixed Output)PROCEDURE (Fixed Output Voltage Version)EXAMPLE (Fixed Output Voltage Version)To simplify the buck regulator design procedure,NationalSemiconductor is making available computer design software to be used with the SIMPLE SWITCHER line of switchingregulators.LM267X Made Simple version 6.0is available on Windows ®3.1,NT,or 95operating systems.Given:Given:V OUT =Regulated Output Voltage (3.3V,5V,or 12V)V OUT =5V V IN (max)=Maximum DC Input Voltage V IN (max)=12V I LOAD (max)=Maximum Load Current I LOAD (max)=1A 1.Inductor Selection (L1)1.Inductor Selection (L1)A.Select the correct inductor value selection guide from Figure 4,Figure 5or Figure 6(output voltages of 3.3V,5V,or 12V respectively).For all other voltages,see the design procedure for the adjustable version.e the inductor selection guide for the 5V version shown in Figure 5.B.From the inductor value selection guide,identify theinductance region intersected by the Maximum Input Voltage line and the Maximum Load Current line.Each region isidentified by an inductance value and an inductor code (LXX). B.From the inductor value selection guide shown in Figure 5,the inductance region intersected by the 12V horizontal line and the 1A vertical line is 33µH,and the inductor code is L23.C.Select an appropriate inductor from the four manufacturer’s part numbers listed in Figure 8.Each manufacturer makes a different style of inductor to allow flexibility in meeting various design requirements.Listed below are some of thedifferentiating characteristics of each manufacturer’s inductors: C.The inductance value required is 33µH.From the table in Figure 8,go to the L23line and choose an inductor part number from any of the four manufacturers shown.(In most instances,both through hole and surface mount inductors are available.)Schott:ferrite EP core inductors;these have very low leakage magnetic fields to reduce electro-magnetic interference (EMI)and are the lowest power loss inductorsRenco:ferrite stick core inductors;benefits are typically lowest cost inductors and can withstand E •T and transient peakcurrents above rated value.Be aware that these inductors have an external magnetic field which may generate more EMI than other types of inductors.Pulse:powered iron toroid core inductors;these can also be low cost and can withstand larger than normal E •T and transient peak currents.Toroid inductors have low EMI.Coilcraft:ferrite drum core inductors;these are the smallest physical size inductors,available only as SMT components.Be aware that these inductors also generate EMI —but less than stick inductors.Complete specifications for these inductors are available from the respective manufacturers.A table listing the manufacturers’phone numbers is located in Figure 9.2.Output Capacitor Selection (C OUT )2.Output Capacitor Selection (C OUT )A.Select an output capacitor from the output capacitor table in Figure ing the output voltage and the inductance value found in the inductor selection guide,step 1,locate the appropriate capacitor value and voltage rating.e the 5.0V section in the output capacitor table in Figure 10.Choose a capacitor value and voltage rating from the line that contains the inductance value of 33µH.The capacitance and voltage rating values corresponding to the 33µH inductor are the:L M 2675 10LM2675Series Buck Regulator Design Procedure(Fixed Output)(Continued) PROCEDURE(Fixed Output Voltage Version)EXAMPLE(Fixed Output Voltage Version)The capacitor list contains through-hole electrolytic capacitors from four different capacitor manufacturers and surface mount tantalum capacitors from two different capacitor manufacturers. It is recommended that both the manufacturers and the manufacturer’s series that are listed in the table be used.A table listing the manufacturers’phone numbers is located in Figure11.Surface Mount:68µF/10V Sprague594D Series.100µF/10V AVX TPS Series. Through Hole:68µF/10V Sanyo OS-CON SA Series. 220µF/35V Sanyo MV-GX Series. 220µF/35V Nichicon PL Series.220µF/35V Panasonic HFQ Series.3.Catch Diode Selection(D1)A.In normal operation,the average current of the catch diode is the load current times the catch diode duty cycle,1-D(D is the switch duty cycle,which is approximately the output voltage divided by the input voltage).The largest value of the catch diode average current occurs at the maximum load current and maximum input voltage(minimum D).For normal operation,the catch diode current rating must be at least1.3times greater than its maximum average current.However,if the power supply design must withstand a continuous output short,the diode should have a current rating equal to the maximum current limit of the LM2675.The most stressful condition for this diode is a shorted output condition.3.Catch Diode Selection(D1)A.Refer to the table shown in Figure12.In this example,a1A, 20V Schottky diode will provide the best performance.If the circuit must withstand a continuous shorted output,a higher current Schottky diode is recommended.B.The reverse voltage rating of the diode should be at least1.25times the maximum input voltage.C.Because of their fast switching speed and low forwardvoltage drop,Schottky diodes provide the best performance andefficiency.This Schottky diode must be located close to theLM2675using short leads and short printed circuit traces.4.Input Capacitor(C IN) 4.Input Capacitor(C IN)LM2675LM2675Series Buck Regulator Design Procedure (Fixed Output)(Continued)PROCEDURE (Fixed Output Voltage Version)EXAMPLE (Fixed Output Voltage Version)A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large voltagetransients from appearing at the input.This capacitor should be located close to the IC using short leads.In addition,the RMS current rating of the input capacitor should be selected to be at least 1⁄2the DC load current.The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded.The curves shown in Figure 14show typical RMS current ratings for several different aluminum electrolytic capacitor values.A parallel connection of two or morecapacitors may be required to increase the total minimum RMS current rating to suit the application requirements.For an aluminum electrolytic capacitor,the voltage rating should be at least 1.25times the maximum input voltage.Caution must be exercised if solid tantalum capacitors are used.The tantalum capacitor voltage rating should be twice the maximum input voltage.The tables in Figure 15show the recommendedapplication voltage for AVX TPS and Sprague 594D tantalum capacitors.It is also recommended that they be surge current tested by the manufacturer.The TPS series available from AVX,and the 593D and 594D series from Sprague are all surgecurrent tested.Another approach to minimize the surge current stresses on the input capacitor is to add a small inductor in series with the input supply line.Use caution when using ceramic capacitors for input bypassing,because it may cause severe ringing at the V IN pin.The important parameters for the input capacitor are the input voltage rating and the RMS current rating.With a maximum input voltage of 12V,an aluminum electrolytic capacitor with a voltage rating greater than 15V (1.25x V IN )would be needed.The next higher capacitor voltage rating is 16V.The RMS current rating requirement for the input capacitor in a buck regulator is approximately 1⁄2the DC load current.In this example,with a 1A load,a capacitor with a RMS current rating of at least 500mA is needed.The curves shown in Figure 14can be used to select an appropriate input capacitor.From the curves,locate the 16V line and note which capacitor values have RMS current ratings greater than 500mA.For a through hole design,a 330µF/16V electrolytic capacitor (Panasonic HFQ series,Nichicon PL,Sanyo MV-GX series or equivalent)would be adequate.Other types or othermanufacturers’capacitors can be used provided the RMS ripple current ratings are adequate.Additionally,for a completesurface mount design,electrolytic capacitors such as the Sanyo CV-C or CV-BS and the Nichicon WF or UR and the NIC Components NACZ series could be considered.For surface mount designs,solid tantalum capacitors can be used,but caution must be exercised with regard to the capacitor surge current rating and voltage rating.In this example,checking Figure 15,and the Sprague 594D series datasheet,a Sprague 594D 15µF,25V capacitor is adequate.5.Boost Capacitor (C B )5.Boost Capacitor (C B )This capacitor develops the necessary voltage to turn the switch gate on fully.All applications should use a 0.01µF,50V ceramic capacitor.For this application,and all applications,use a 0.01µF,50V ceramic capacitor.L M 2675LM2675Series Buck Regulator Design Procedure(Fixed Output)(Continued) Inductor Value Selection Guides(For Continuous Mode Operation)01280326FIGURE4.LM2675-3.301280327 FIGURE5.LM2675-5.001280328FIGURE6.LM2675-1201280329FIGURE7.LM2675-ADJLM2675LM2675Series Buck Regulator Design Procedure (Fixed Output)(Continued)Ind.Ref.Desg.Inductance (µH)Current (A)SchottRencoPulse Engineering Coilcraft Through Surface ThroughSurface Through Surface Surface HoleMountHole Mount HoleMountMountL4680.326714394067144310RL-1284-68-43RL1500-68PE-53804PE-53804-S DO1608-683L5470.376714831067148420RL-1284-47-43RL1500-47PE-53805PE-53805-S DO1608-473L6330.446714832067148430RL-1284-33-43RL1500-33PE-53806PE-53806-S DO1608-333L7220.526714833067148440RL-1284-22-43RL1500-22PE-53807PE-53807-S DO1608-223L92200.326714396067144330RL-5470-3RL1500-220PE-53809PE-53809-S DO3308-224L101500.396714397067144340RL-5470-4RL1500-150PE-53810PE-53810-S DO3308-154L111000.486714398067144350RL-5470-5RL1500-100PE-53811PE-53811-S DO3308-104L12680.586714399067144360RL-5470-6RL1500-68PE-53812PE-53812-S DO3308-683L13470.706714400067144380RL-5470-7RL1500-47PE-53813PE-53813-S DO3308-473L14330.836714834067148450RL-1284-33-43RL1500-33PE-53814PE-53814-S DO3308-333L15220.996714835067148460RL-1284-22-43RL1500-22PE-53815PE-53815-S DO3308-223L182200.556714404067144420RL-5471-2RL1500-220PE-53818PE-53818-S DO3316-224L191500.666714405067144430RL-5471-3RL1500-150PE-53819PE-53819-S DO3316-154L201000.826714406067144440RL-5471-4RL1500-100PE-53820PE-53820-S DO3316-104L21680.996714407067144450RL-5471-5RL1500-68PE-53821PE-53821-S DO3316-683L2247 1.176714408067144460RL-5471-6—PE-53822PE-53822-S DO3316-473L2333 1.406714409067144470RL-5471-7—PE-53823PE-53823-S DO3316-333L2422 1.706714837067148480RL-1283-22-43—PE-53824PE-53824-S DO3316-223L27220 1.006714411067144490RL-5471-2—PE-53827PE-53827-S DO5022P-224L28150 1.206714412067144500RL-5471-3—PE-53828PE-53828-S DO5022P-154L29100 1.476714413067144510RL-5471-4—PE-53829PE-53829-S DO5022P-104L30681.786714414067144520RL-5471-5—PE-53830PE-53830-SDO5022P-683FIGURE 8.Inductor Manufacturers’Part NumbersCoilcraft Inc.Phone (800)322-2645FAX (708)639-1469Coilcraft Inc.,Europe Phone +441236730595FAX +441236730627Pulse Engineering Inc.Phone (619)674-8100FAX (619)674-8262Pulse Engineering Inc.,Phone +3539324107EuropeFAX +3539324459Renco Electronics Inc.Phone (800)645-5828FAX (516)586-5562Schott Corp.Phone (612)475-1173FAX(612)475-1786FIGURE 9.Inductor Manufacturers’Phone NumbersL M 2675LM2675Series Buck Regulator Design Procedure(Fixed Output)(Continued)Output Voltage(V)Inductance(µH)Output CapacitorSurface Mount Through HoleSprague AVX TPS Sanyo OS-CON Sanyo MV-GX Nichicon Panasonic594D Series Series SA Series Series PL Series HFQ Series (µF/V)(µF/V)(µF/V)(µF/V)(µF/V)(µF/V)3.322120/6.3100/10100/10330/35330/35330/35 33120/6.3100/1068/10220/35220/35220/35 4768/10100/1068/10150/35150/35150/35 68120/6.3100/10100/10120/35120/35120/35 100120/6.3100/10100/10120/35120/35120/35 150120/6.3100/10100/10120/35120/35120/355.022100/16100/10100/10330/35330/35330/35 3368/101001068/10220/35220/35220/35 4768/10100/1068/10150/35150/35150/35 68100/16100/10100/10120/35120/35120/35 100100/16100/10100/10120/35120/35120/35 150100/16100/10100/10120/35120/35120/351222120/20(2x)68/2068/20330/35330/35330/353368/2568/2068/20220/35220/35220/354747/2068/2047/20150/35150/35150/356847/2068/2047/20120/35120/35120/3510047/2068/2047/20120/35120/35120/3515047/2068/2047/20120/35120/35120/3522047/2068/2047/20120/35120/35120/35FIGURE10.Output Capacitor TableNichicon Corp.Phone(847)843-7500FAX(847)843-2798Panasonic Phone(714)373-7857FAX(714)373-7102AVX Corp.Phone(803)448-9411FAX(803)448-1943Sprague/Vishay Phone(207)324-4140FAX(207)324-7223Sanyo Corp.Phone(619)661-6322FAX(619)661-1055FIGURE11.Capacitor Manufacturers’Phone NumbersLM2675LM2675Series Buck Regulator Design Procedure (Fixed Output)(Continued)V R 1A Diodes3A Diodes Surface Through Surface Through Mount Hole Mount Hole 20V SK121N5817SK321N5820B120SR102SR30230VSK131N5818SK331N5821B13011DQ0330WQ03F31DQ03MBRS130SR10340VSK141N5819SK341N5822B14011DQ0430BQ040MBR340MBRS140SR10430WQ04F 31DQ0410BQ040MBRS340SR30410MQ040MBRD34015MQ04050VSK15MBR150SK35MBR350B15011DQ0530WQ05F31DQ0510BQ050SR105SR305FIGURE 12.Schottky Diode Selection TableInternational Rectifier Corp.Phone (310)322-3331FAX (310)322-3332Motorola,Inc.Phone (800)521-6274FAX (602)244-6609General Instruments Corp.Phone (516)847-3000FAX (516)847-3236Diodes,Inc.Phone (805)446-4800FAX(805)446-4850FIGURE 13.Diode Manufacturers’Phone Numbers01280330FIGURE 14.RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)L M 2675LM2675Series Buck Regulator Design Procedure(Fixed Output)(Continued)LM2675Series Buck Regulator Design Procedure(Adjustable Output)PROCEDURE(Adjustable Output Voltage Version)EXAMPLE(Adjustable Output Voltage Version) To simplify the buck regulator design procedure,NationalSemiconductor is making available computer design software tobe used with the SIMPLE SWITCHER line of switchingregulators.LM267X Made Simple version6.0is available foruse on Windows3.1,NT,or95operating systems.Given:Given:V OUT=Regulated Output Voltage V OUT=20VV IN(max)=Maximum Input Voltage V IN(max)=28VI LOAD(max)=Maximum Load Current I LOAD(max)=1AF=Switching Frequency(Fixed at a nominal260kHz).F=Switching Frequency(Fixed at a nominal260kHz).1.Programming Output Voltage(Selecting R1and R2,as shown in Figure3)1.Programming Output Voltage(Selecting R1and R2,as shown in Figure3)Use the following formula to select the appropriate resistorvalues.Select R1to be1kΩ,1%.Solve for R2. where V REF=1.21VSelect a value for R1between240Ωand1.5kΩ.The lower resistor values minimize noise pickup in the sensitive feedback pin.(For the lowest temperature coefficient and the best stability with time,use1%metal film resistors.)R2=1k(16.53−1)=15.53kΩ,closest1%value is15.4kΩ. R2=15.4kΩ.AVX TPSRecommended VoltageApplication Voltage Rating+85˚C Rating3.3 6.3510102012251535Sprague594DRecommended VoltageApplication Voltage Rating+85˚C Rating2.543.3 6.35108161220182524352950FIGURE15.LM2675。
