电源芯片资料LM2577

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LM2578AM资料

LM2578A/LM3578A Switching RegulatorGeneral DescriptionThe LM2578A is a switching regulator which can easily be set up for such DC-to-DC voltage conversion circuits as the buck,boost,and inverting configurations.The LM2578A fea-tures a unique comparator input stage which not only has separate pins for both the inverting and non-inverting inputs, but also provides an internal1.0V reference to each input, thereby simplifying circuit design and p.c.board layout.The output can switch up to750mA and has output pins for its collector and emitter to promote design flexibility.An external current limit terminal may be referenced to either the ground or the V in terminal,depending upon the application.In addi-tion,the LM2578A has an on board oscillator,which sets the switching frequency with a single external capacitor from<1 Hz to100kHz(typical).The LM2578A is an improved version of the LM2578,offer-ing higher maximum ratings for the total supply voltage and output transistor emitter and collector voltages.Featuresn Inverting and non-inverting feedback inputsn 1.0V reference at inputsn Operates from supply voltages of2V to40Vn Output current up to750mA,saturation less than0.9V n Current limit and thermal shut downn Duty cycle up to90%Applicationsn Switching regulators in buck,boost,inverting,and single-ended transformer configurationsn Motor speed controln Lamp flasherConnection Diagram and Ordering InformationDual-In-Line Package00871129Order Number LM3578AM,LM2578AN or LM3578ANSee NS Package Number M08A or N08E February2005LM2578A/LM3578A Switching Regulator©2005National Semiconductor Corporation Functional Diagram00871101L M 2578A /L M 3578A 2Absolute Maximum Ratings(Note1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.Total Supply Voltage50V Collector Output to Ground−0.3V to+50V Emitter Output to Ground(Note2)−1V to+50V Power Dissipation(Note3)Internally limited Output Current750mA Storage Temperature−65˚C to+150˚C Lead Temperature(soldering,10seconds)260˚C Maximum Junction Temperature150˚CESD Tolerance(Note4)2kVOperating RatingsAmbient Temperature RangeLM2578A−40˚C≤T A≤+85˚C LM3578A0˚C≤T A≤+70˚C Junction Temperature RangeLM2578A−40˚C≤T J≤+125˚C LM3578A0˚C≤T J≤+125˚CElectrical CharacteristicsThese specifications apply for2V≤V IN≤40V(2.2V≤V IN≤40V for T J≤−25˚C),timing capacitor C T=3900pF,and25%≤duty cycle≤75%,unless otherwise specified.Values in standard typeface are for T J=25˚C;values in boldface type apply for operation over the specified operating junction temperature range.LM2578A/Symbol Parameter Conditions Typical LM3578A Units(Note5)Limit(Note6) OSCILLATORf OSC Frequency20kHz24kHz(max)16kHz(min)∆f OSC/∆T Frequency Drift with Temperature−0.13%/˚C Amplitude550mV p-p REFERENCE/COMPARATOR(Note7)V R Input Reference I1=I2=0mA and 1.0V Voltage I1=I2=1mA±1%(Note8) 1.050/1.070V(max)0.950/0.930V(min)∆V R/∆V IN Input Reference Voltage LineRegulationI1=I2=0mA and0.003%/VI1=I2=1mA±1%(Note8)0.01/0.02%/V(max) I INV Inverting Input Current I1=I2=0mA,duty cycle=25%0.5µALevel Shift Accuracy Level Shift Current=1mA 1.0%10/13%(max)∆V R/∆t Input Reference Voltage Long TermStability100ppm/1000h OUTPUTV C(sat)Collector Saturation Voltage I C=750mA pulsed,Emittergrounded 0.7V0.90/1.2V(max)V E(sat)Emitter Saturation Voltage I O=80mA pulsed, 1.4VV IN=V C=40V 1.7/2.0V(max)I CES Collector Leakage Current V IN=V CE=40V,Emitter grounded,Output OFF 0.1µA200/250µA(max)BV CEO(SUS)Collector-Emitter Sustaining Voltage I SUST=0.2A(pulsed),V IN=060V50V(min) CURRENT LIMITV CL Sense Voltage Shutdown Level Referred to V IN or Ground110mV(Note9)80mV(min)160mV(max)LM2578A/LM3578A3Electrical Characteristics(Continued)These specifications apply for 2V ≤V IN ≤40V (2.2V ≤V IN ≤40V for T J ≤−25˚C),timing capacitor C T =3900pF,and 25%≤duty cycle ≤75%,unless otherwise specified.Values in standard typeface are for T J =25˚C;values in boldface type apply for operation over the specified operating junction temperature range.LM2578A/Symbol ParameterConditionsTypical LM3578A Units(Note 5)Limit (Note 6)CURRENT LIMIT ∆V CL /∆T Sense Voltage Temperature Drift 0.3%/˚C I CLSense Bias CurrentReferred to V IN 4.0µA Referred to ground0.4µA DEVICE POWER CONSUMPTION I SSupply CurrentOutput OFF,V E =0V2.0mA3.5/4.0mA (max)Output ON,I C =750mA pulsed,14mAV E =0VNote 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions.Note 2:For T J ≥100˚C,the Emitter pin voltage should not be driven more than 0.6V below ground (see Application Information).Note 3:At elevated temperatures,devices must be derated based on package thermal resistance.The device in the 8-pin DIP must be derated at 95˚C/W,junction to ambient.The device in the surface-mount package must be derated at 150˚C/W,junction-to-ambient.Note 4:Human body model,1.5k Ωin series with 100pF.Note 5:Typical values are for T J =25˚C and represent the most likely parametric norm.Note 6:All limits guaranteed at room temperature (standard type face)and at temperature extremes (bold type face).Room temperature limits are 100%production tested.Limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC)methods.All limits are used to calculate AOQL.Note 7:Input terminals are protected from accidental shorts to ground but if external voltages higher than the reference voltage are applied,excessive current will flow and should be limited to less than 5mA.Note 8:I 1and I 2are the external sink currents at the inputs (refer to Test Circuit).Note 9:Connection of a 10k Ωresistor from pin 1to pin 4will drive the duty cycle to its maximum,typically 90%.Applying the minimum Current Limit Sense Voltage to pin 7will not reduce the duty cycle to less than 50%.Applying the maximum Current Limit Sense Voltage to pin 7is certain to reduce the duty cycle below 50%.Increasing this voltage by 15mV may be required to reduce the duty cycle to 0%,when the Collector output swing is 40V or greater (see Ground-Referred Current Limit Sense Voltage typical curve).Typical Performance CharacteristicsOscillator Frequency Changewith TemperatureOscillator Voltage Swing0087113200871133L M 2578A /L M 3578A 4Typical Performance Characteristics(Continued)Input Reference Voltage Drift with TemperatureCollector Saturation Voltage(Sinking Current,Emitter Grounded)0087113400871135Emitter Saturation Voltage(Sourcing Current,Collector at V in )Ground ReferredCurrent Limit Sense Voltage0087113600871137Current Limit Sense Voltage Drift with Temperature Current Limit Response Time for Various Over Drives0087113800871139LM2578A/LM3578A5Typical Performance Characteristics(Continued)Current Limit Sense Voltagevs Supply VoltageSupply Current0087114000871141Supply CurrentCollector Current with Emitter Output Below Ground0087114200871143Test Circuit*Parameter tests can be made using the test circuit shown.Select the desired V in ,collector voltage and duty cycle with adjustable power supplies.A digital volt meter with an input resistance greater than 100M Ωshould be used to measure the following:Input Reference Voltage to Ground;S1in either position.Level Shift Accuracy (%)=(T P3(V)/1V)x 100%;S1at I 1=I 2=1mAInput Current (mA)=(1V −T p3(V))/1M Ω:S1at I 1=I 2=0mA.Oscillator parameters can be measured at T p4using a fre-quency counter or an oscilloscope.The Current Limit Sense Voltage is measured by connecting an adjustable 0-to-1V floating power supply in series with the current limit terminal and referring it to either the ground or the V in terminal.Set the duty cycle to 90%and monitor test point T P5while adjusting the floating power supply voltage until the LM2578A’s duty cycle just reaches 0%.This voltage is the Current Limit Sense Voltage.The Supply Current should be measured with the duty cycle at 0%and S1in the I 1=I 2=0mA position.*LM2578A specifications are measured using automated test equipment.This circuit is provided for the customer’s convenience when checking parameters.Due to possible variations in testing conditions,the measured values from these testing procedures may not match those of the factory.L M 2578A /L M 3578A 6Test Circuit*(Continued)00871103 Op amp supplies are±15VDVM input resistance>100MΩ*LM2578max duty cycle is90%Definition of TermsInput Reference Voltage:The voltage(referred to ground) that must be applied to either the inverting or non-inverting input to cause the regulator switch to change state(ON or OFF).Input Reference Current:The current that must be drawn from either the inverting or non-inverting input to cause the regulator switch to change state(ON or OFF).Input Level Shift Accuracy:This specification determines the output voltage tolerance of a regulator whose output control depends on drawing equal currents from the inverting and non-inverting inputs(see the Inverting Regulator of Fig-ure21,and the RS-232Line Driver Power Supply of Figure 23).Level Shift Accuracy is tested by using two equal-value resistors to draw current from the inverting and non-inverting input terminals,then measuring the percentage difference in the voltages across the resistors that produces a controlled duty cycle at the switch output.Collector Saturation Voltage:With the inverting input ter-minal grounded thru a10kΩresistor and the output transis-tor’s emitter connected to ground,the Collector Saturation-Voltage is the collector-to-emitter voltage for a given collector current.Emitter Saturation Voltage:With the inverting input termi-nal grounded thru a10kΩresistor and the output transistor’s collector connected to V in,the Emitter Saturation Voltage is the collector-to-emitter voltage for a given emitter current. Collector Emitter Sustaining Voltage:The collector-emitter breakdown voltage of the output transistor,mea-sured at a specified current.Current Limit Sense Voltage:The voltage at the CurrentLimit pin,referred to either the supply or the ground terminal,which(via logic circuitry)will cause the output transistor toturn OFF and resets cycle-by-cycle at the oscillator fre-quency.Current Limit Sense Current:The bias current for theCurrent Limit terminal with the applied voltage equal to theCurrent Limit Sense Voltage.Supply Current:The IC power supply current,excluding thecurrent drawn through the output transistor,with the oscilla-tor operating.Functional DescriptionThe LM2578A is a pulse-width modulator designed for useas a switching regulator controller.It may also be used inother applications which require controlled pulse-width volt-age drive.A control signal,usually representing output voltage,fed intothe LM2578A’s comparator is compared with an internally-generated reference.The resulting error signal and the os-cillator’s output are fed to a logic network which determineswhen the output transistor will be turned ON or OFF.Thefollowing is a brief description of the subsections of theLM2578A.COMPARATOR INPUT STAGEThe LM2578A’s comparator input stage is unique in that boththe inverting and non-inverting inputs are available to theuser,and both contain a1.0V reference.This is accom-plished as follows:A1.0V reference is fed into a modifiedvoltage follower circuit(see FUNCTIONAL DIAGRAM).When both input pins are open,no current flows through R1LM2578A/LM3578A7Functional Description(Continued)and R2.Thus,both inputs to the comparator will have the potential of the 1.0V reference,V A .When one input,for example the non-inverting input,is pulled ∆V away from V A ,a current of ∆V/R1will flow through R1.This same current flows through R2,and the comparator sees a total voltage of 2∆V between its inputs.The high gain of the system,through feedback,will correct for this imbalance and return both inputs to the 1.0V level.This unusual comparator input stage increases circuit flex-ibility,while minimizing the total number of external compo-nents required for a voltage regulator system.The inverting switching regulator configuration,for example,can be set up without having to use an external op amp for feedback polarity reversal (see TYPICAL APPLICATIONS).OSCILLATORThe LM2578A provides an on-board oscillator which can be adjusted up to 100kHz.Its frequency is set by a single external capacitor,C 1,as shown in Figure 1,and follows the equationf OSC =8x10−5/C 1The oscillator provides a blanking pulse to limit maximum duty cycle to 90%,and a reset pulse to the internal circuitry.OUTPUT TRANSISTORThe output transistor is capable of delivering up to 750mA with a saturation voltage of less than 0.9V.(see Collector Saturation Voltage and Emitter Saturation Voltage curves).The emitter must not be pulled more than 1V below ground (this limit is 0.6V for T J ≥100˚C).Because of this limit,an external transistor must be used to develop negative output voltages (see the Inverting Regulator Typical Application).Other configurations may need protection against violation of this limit (see the Emitter Output section of the Applica-tions Information).CURRENT LIMITThe LM2578A’s current limit may be referenced to either the ground or the V in pins,and operates on a cycle-by-cycle basis.The current limit section consists of two comparators:one with its non-inverting input referenced to a voltage 110mV below V in ,the other with its inverting input referenced110mV above ground (see FUNCTIONAL DIAGRAM).The current limit is activated whenever the current limit terminal is pulled 110mV away from either V in or ground.Applications InformationCURRENT LIMITAs mentioned in the functional description,the current limit terminal may be referenced to either the V in or the ground terminal.Resistor R3converts the current to be sensed into a voltage for current limit detection.CURRENT LIMIT TRANSIENT SUPPRESSIONWhen noise spikes and switching transients interfere with proper current limit operation,R1and C1act together as a low pass filter to control the current limit circuitry’s response time.Because the sense current of the current limit terminal varies according to where it is referenced,R1should be less than 2k Ωwhen referenced to ground,and less than 100Ωwhen referenced to V in .00871104FIGURE 1.Value of Timing Capacitor vsOscillator Frequency00871115FIGURE 2.Current Limit,Ground Referred00871116FIGURE 3.Current Limit,V in ReferredL M 2578A /L M 3578A 8Applications Information(Continued)C.L.SENSE VOLTAGE MULTIPLICATIONWhen a larger sense resistor value is desired,the voltage divider network,consisting of R1and R2,may be used.This effectively multiplies the sense voltage by(1+R1/R2).Also, R1can be replaced by a diode to increase current limit sense voltage to about800mV(diode V f+110mV).UNDER-VOLTAGE LOCKOUTUnder-voltage lockout is accomplished with few external components.When V in becomes lower than the zener breakdown voltage,the output transistor is turned off.This occurs because diode D1will then become forward biased, allowing resistor R3to sink a greater current from the non-inverting input than is sunk by the parallel combination of R1 and R2at the inverting terminal.R3should be one-fifth of the value of R1and R2in parallel.MAXIMUM DUTY CYCLE LIMITINGThe maximum duty cycle can be externally limited by adjust-ing the charge to discharge ratio of the oscillator capacitor with a single external resistor.Typical values are50µA for the charge current,450µA for the discharge current,and a voltage swing from200mV to750mV.Therefore,R1is selected for the desired charging and discharging slopes and C1is readjusted to set the oscillator frequency.00871117 FIGURE4.Current Limit Transient Suppressor,Ground Referred00871118 FIGURE5.Current Limit Transient Suppressor,V in Referred00871119 FIGURE6.Current Limit Sense Voltage Multiplication,Ground Referred00871120FIGURE7.Current Limit Sense Voltage Multiplication,V in Referred00871122FIGURE8.Under-Voltage LockoutLM2578A/LM3578A9Applications Information(Continued)DUTY CYCLE ADJUSTMENTWhen manual or mechanical selection of the output transis-tor’s duty cycle is needed,the cirucit shown below may be used.The output will turn on with the beginning of each oscillator cycle and turn off when the current sunk by R2and R3from the non-inverting terminal becomes greater than the current sunk from the inverting terminal.With the resistor values as shown,R3can be used to adjust the duty cycle from 0%to 90%.When the sum of R2and R3is twice the value of R1,the duty cycle will be about 50%.C1may be a large electrolytic capacitor to lower the oscillator frequency below 1Hz.REMOTE SHUTDOWNThe LM2578A may be remotely shutdown by sinking a greater current from the non-inverting input than from the inverting input.This may be accomplished by selecting re-sistor R3to be approximately one-half the value of R1and R2in parallel.EMITTER OUTPUTWhen the LM2578A output transistor is in the OFF state,if the Emitter output swings below the ground pin voltage,the output transistor will turn ON because its base is clamped near ground.The Collector Current with Emitter Output Be-low Ground curve shows the amount of Collector current drawn in this mode,vs temperature and Emitter voltage.When the Collector-Emitter voltage is high,this current will cause high power dissipation in the output transistor and should be avoided.This situation can occur in the high-current high-voltage buck application if the Emitter output is used and the catch diode’s forward voltage drop is greater than 0.6V.A fast-recovery diode can be added in series with the Emitter output to counter the forward voltage drop of the catch diode (see Figure 2).For better efficiency of a high output current buck regulator,an external PNP transistor should be used as shown in Figure 16.SYNCHRONIZING DEVICESWhen several devices are to be operated at once,their oscillators may be synchronized by the application of an external signal.This drive signal should be a pulse waveform with a minimum pulse width of 2µs.and an amplitude from00871121FIGURE 9.Maximum Duty Cycle Limiting00871123FIGURE 10.Duty Cycle Adjustment00871124FIGURE 11.Shutdown Occurs when V L is High00871130FIGURE 12.D1Prevents Output Transistor from Improperly Turning ON due to D2’s Forward Voltage L M 2578A /L M 3578A 10Applications Information(Continued)1.5V to2.0V.The signal source must be capable of 1.)driving capacitive loads and 2.)delivering up to 500µA for each LM2578A.Capacitors C1thru CN are to be selected for a 20%slower frequency than the synchronization frequency.Typical ApplicationsThe LM2578A may be operated in either the continuous or the discontinuous conduction mode.The following applica-tions (except for the Buck-Boost Regulator)are designed for continuous conduction operation.That is,the inductor cur-rent is not allowed to fall to zero.This mode of operation has higher efficiency and lower EMI characteristics than the dis-continuous mode.BUCK REGULATORThe buck configuration is used to step an input voltage down to a lower level.Transistor Q1in Figure 14chops the input DC voltage into a squarewave.This squarewave is then converted back into a DC voltage of lower magnitude by the low pass filter consisting of L1and C1.The duty cycle,D,of the squarewave relates the output voltage to the input volt-age by the following equation:V out =D x V in =V in x (t on )/(t on +t off ).Figure 15is a 15V to 5V buck regulator with an output current,I o ,of 350mA.The circuit becomes discontinuous at 20%of I o(max),has 10mV of output voltage ripple,an effi-ciency of 75%,a load regulation of 30mV (70mA to 350mA)and a line regulation of 10mV (12≤V in ≤18V).Component values are selected as follows:R1=(V o −1)x R2where R2=10k ΩR3=V/I sw(max)R3=0.15Ωwhere:V is the current limit sense voltage,0.11VI sw(max)is the maximum allowable current thru the output transistor.L1is the inductor and may be found from the inductance calculation chart (Figure 16)as follows:Given V in =15VV o =5VI o(max)=350mA f OSC =50kHzDiscontinuous at 20%of I o(max).Note that since the circuit will become discontinuous at 20%of I o(max),the load current must not be allowed to fall below 70mA.00871125FIGURE 13.Synchronizing Devices00871105FIGURE 14.Basic Buck RegulatorLM2578A/LM3578A11Typical Applications(Continued)00871106V in =15V R3=0.15ΩV o =5V C1=1820pF V ripple =10mV C2=220µF I o =350mA C3=20pF f osc =50kHz L1=470µH R1=40k ΩD1=1N5818R2=10k ΩFIGURE 15.Buck or Step-Down RegulatorL M 2578A /L M 3578A 12LM2578A/LM3578A Typical Applications(Continued)00871131FIGURE16.DC/DC Inductance Calculator13Typical Applications(Continued)Step 1:Calculate the maximum DC current through the inductor,I L(max).The necessary equations are indicated at the top of the chart and show that I L(max)=I o(max)for the buck configuration.Thus,I L(max)=350mA.Step 2:Calculate the inductor Volts-sec product,E-T op ,according to the equations given from the chart.For the Buck:E-T op =(V in −V o )(V o /V in )(1000/f osc )=(15−5)(5/15)(1000/50)=66V-µs.with the oscillator frequency,f osc ,expressed in kHz.Step 3:Using the graph with axis labeled “Discontinuous At %I OUT ”and “I L(max,DC)”find the point where the desired maximum inductor current,I L(max,DC)intercepts the desired discontinuity percentage.In this example,the point of interest is where the 0.35A line intersects with the 20%line.This is nearly the midpoint of the horizontal axis.Step 4:This last step is merely the translation of the point found in Step 3to the graph directly below it.This is accom-plished by moving straight down the page to the point which intercepts the desired E-T op .For this example,E-T op is 66V-µs and the desired inductor value is 470µH.Since this example was for 20%discontinuity,the bottom chart could have been used directly,as noted in step 3of the chart instructions.For a full line of standard inductor values,contact Pulse Engineering (San Diego,Calif.)regarding their PE526XX series,or A.I.E.Magnetics (Nashville,Tenn.).A more precise inductance value may be calculated for the Buck,Boost and Inverting Regulators as follows:BUCKL =V o (V in −V o )/(∆I L V in f osc )BOOSTL =V in (V o −V in )/(∆I L f osc V o )INVERTL =V in |V o |/[∆I L (V in +|V o |)f osc ]where ∆I L is the current ripple through the inductor.∆I L is usually chosen based on the minimum load current expected of the circuit.For the buck regulator,since the inductor current I L equals the load current I O ,∆I L =2•I O(min)∆I L =140mA for this circuit.∆I L can also be interpreted as ∆I L =2•(Discontinuity Factor)•I Lwhere the Discontinuity Factor is the ratio of the minimum load current to the maximum load current.For this example,the Discontinuity Factor is 0.2.The remainder of the components of Figure 15are chosen as follows:C1is the timing capacitor found in Figure 1.C2≥V o (V in −V o )/(8f osc 2V in V ripple L1)where V ripple is the peak-to-peak output voltage ripple.C3is necessary for continuous operation and is generally in the 10pF to 30pF range.D1should be a Schottky type diode,such as the 1N5818or 1N5819.BUCK WITH BOOSTED OUTPUT CURRENTFor applications requiring a large output current,an external transistor may be used as shown in Figure 17.This circuit steps a 15V supply down to 5V with 1.5A of output current.The output ripple is 50mV,with an efficiency of 80%,a load regulation of 40mV (150mA to 1.5A),and a line regulation of 20mV (12V ≤V in ≤18V).Component values are selected as outlined for the buck regulator with a discontinuity factor of 10%,with the addition of R4and R5:R4=10V BE1B f /I pR5=(V in −V −V BE1−V sat )B f /(I L(max,DC)+I R4)where:V BE1is the V BE of transistor Q1.V sat is the saturation voltage of the LM2578A output transis-tor.V is the current limit sense voltage.B f is the forced current gain of transistor Q1(B f =30for Figure 17).I R4=V BE1/R4I p =I L(max,DC)+0.5∆I LL M 2578A /L M 3578A 14Typical Applications(Continued)BOOST REGULATORThe boost regulator converts a low input voltage into a higher output voltage.The basic configuration is shown in Figure 18.Energy is stored in the inductor while the transis-tor is on and then transferred with the input voltage to the output capacitor for filtering when the transistor is off.Thus,V o =V in +V in (t on /t off ).The circuit of Figure 19converts a 5V supply into a 15V supply with 150mA of output current,a load regulation of 14mV (30mA to 140mA),and a line regulation of 35mV (4.5V ≤V in ≤8.5V).R1=(V o −1)R2where R2=10k Ω.R3=V/(I L(max,DC)+0.5∆I L )where:∆I L =2(I LOAD(min))(V o /V in )∆I L is 200mA in this example.R4,C3and C4are necessary for continuous operation and are typically 220k Ω,20pF,and 0.0022µF respectively.C1is the timing capacitor found in Figure 1.C2≥I o (V o −V in )/(f osc V o V ripple ).00871108V in =15V R4=200ΩV o =5V R5=330ΩV ripple =50mV C1=1820pF I o =1.5AC2=330µFf osc =50kHz C3=20pF R1=40k ΩL1=220µH R2=10k ΩD1=1N5819R3=0.05ΩQ1=D45FIGURE 17.Buck Converter with Boosted Output Current00871109FIGURE 18.Basic Boost Regulator00871111V in =5V R4=200k ΩV o =15V C1=1820pF V ripple =10mV C2=470µF I o =140mA C3=20pF f osc =50kHz C4=0.0022µF R1=140k ΩL1=330µH R2=10k ΩD1=1N5818R3=0.15ΩFIGURE 19.Boost or Step-Up RegulatorLM2578A/LM3578A15Typical Applications(Continued)D1is a Schottky type diode such as a 1N5818or 1N5819.L1is found as described in the buck converter section,using the inductance chart for Figure 16for the boost configuration and 20%discontinuity.INVERTING REGULATORFigure 20shows the basic configuration for an inverting regulator.The input voltage is of a positive polarity,but the output is negative.The output may be less than,equal to,or greater in magnitude than the input.The relationship be-tween the magnitude of the input voltage and the output voltage is V o =V in x (t on /t off ).Figure 21shows an LM2578A configured as a 5V to −15V polarity inverter with an output current of 300mA,a load regulation of 44mV (60mA to 300mA)and a line regulation of 50mV (4.5V ≤V in ≤8.5V).R1=(|V o |+1)R2where R2=10k Ω.R3=V/(I L(max,DC)+0.5∆I L ).R4=10V BE1B f /(I L (max,DC)+0.5∆I L )where:V,V BE1,V sat ,and B f are defined in the “Buck Converter with Boosted Output Current”section.∆I L =2(I LOAD(min))(V in +|V o |)/V INR5is defined in the “Buck with Boosted Output Current”section.R6serves the same purpose as R4in the Boost Regulator circuit and is typically 220k Ω.C1,C3and C4are defined in the “Boost Regulator”section.C2≥I o |V o |/[f osc (|V o |+V in )V ripple ]L1is found as outlined in the section on buck converters,using the inductance chart of Figure 16for the invert con-figuration and 20%discontinuity.BUCK-BOOST REGULATORThe Buck-Boost Regulator,shown in Figure 22,may step a voltage up or down,depending upon whether or not the desired output voltage is greater or less than the input voltage.In this case,the output voltage is 12V with an input voltage from 9V to 15V.The circuit exhibits an efficiency of 75%,with a load regulation of 60mV (10mA to 100mA)and a line regulation of 52mV.R1=(V o −1)R2where R2=10k ΩR3=V/0.75AR4,C1,C3and C4are defined in the “Boost Regulator”section.D1and D2are Schottky type diodes such as the 1N5818or 1N5819.where:V d is the forward voltage drop of the diodes.V sat is the saturation voltage of the LM2578A output transis-tor.V sat1is the saturation voltage of transistor Q1.L1≥(V in −V sat −V sat1)(t on /I p )00871110FIGURE 20.Basic Inverting Regulator00871112V in =5V R4=190ΩV o =−15V R5=82ΩV ripple =5mV R6=220k ΩI o =300mA C1=1820pF I min =60mAC2=1000µFf osc =50kHz C3=20pF R1=160k ΩC4=0.0022µF R2=10k ΩL1=150µH R3=0.01ΩD1=1N5818FIGURE 21.Inverting RegulatorL M 2578A /L M 3578A16。

lm2577隔离式dcdc开关电源的设计

LM2577隔离式DC/DC开关电源的设计2010-07-24 16:37LM2577隔离式DC/DC开关电源的设计LM2577是National Semicnductor公司生产的一种典型的升压式集成开关电源调整器，广泛应用在许多电子产品的电源电路中。

它具有外接元器件少、输入直流电源电压范围宽(3.5～40V)、输出开关电流达到3A、内部有固定频率(52kHz)振荡器、电流反馈型工作方式、有软启动、电流限制、欠压锁定和热关闭保护等功能。

可以接成简单升压、隔离和多输出电压的开关电源电路。

它的封装有5引脚的TO-220形式与4引脚的TO-3P形式等,输出直流电压有12V、15V和可调(ADJ)。

图1 LM2577-ADJ典型电路典型升压DC/DC电路TO-220封装形式的LM2577-ADJ典型DC/DC升压形式的直流开关稳压电源电路图如图1所示。

它的内部有1.23V和2.5V能隙基准电压单元、52kHz固定频率锯齿波振荡器、RS触发器、晶体管驱动电路和峰值电流可以达到3A的晶体管，还包括峰值电流采样电阻、采样电流放大器、采样电压放大器，共同组成电压、电流误差反馈系统，以达到脉冲宽度调制(PWM)工作方式。

另外，还有软启动、欠压锁定、过流限制及热关断等单元。

如图1所示的直流开关稳压电源只需要外接八个元器件就可以组成一个U o>U i的直接升压电源。

其中反馈取样电阻R1、R2的阻值可以确定直流输出端的电压值。

例如当输出直流电压为+12V时，R1的阻值为17.5kΩ,R2为2kΩ。

隔离式DC/DC开关稳压电源要求利用LM2577设计一个外形尺寸仅为25.4mm×25.4mm×10.1mm(1英寸×1英寸×0.4英寸)隔离式DC/DC开关电源模块,用于医疗设备的隔离检测供电系统。

该电源系统的具体要求如下：(1)输入端输入直流电源电压+12V；(2)隔离双路输出直流电源电压±12V；(3)输出最大平均电流50mA；(4)输出纹波电压小于5mV；(5)输入、输出相互隔离；(6)输入输出之间隔离击穿电压大于2000VDC；(7)具有已经给定的保护措施。

LM2577-12中文资料

LM1577/LM2577SeriesSIMPLE SWITCHER ®Step-Up Voltage RegulatorGeneral DescriptionThe LM1577/LM2577are monolithic integrated circuits that provide all of the power and control functions for step-up (boost),flyback,and forward converter switching regulators.The device is available in three different output voltage ver-sions:12V,15V,and adjustable.Requiring a minimum number of external components,these regulators are cost effective,and simple to use.Listed in this data sheet are a family of standard inductors and flyback transformers designed to work with these switching regula-tors.Included on the chip is a 3.0A NPN switch and its associated protection circuitry,consisting of current and thermal limiting,and undervoltage lockout.Other features include a 52kHz fixed-frequency oscillator that requires no external compo-nents,a soft start mode to reduce in-rush current during start-up,and current mode control for improved rejection of input voltage and output load transients.Featuresn Requires few external componentsn NPN output switches 3.0A,can stand off 65V n Wide input voltage range:3.5V to 40VnCurrent-mode operation for improved transient response,line regulation,and current limit n 52kHz internal oscillatorn Soft-start function reduces in-rush current during start-up n Output switch protected by current limit,under-voltage lockout,and thermal shutdownTypical Applicationsn Simple boost regulatorn Flyback and forward regulators n Multiple-output regulatorTypical ApplicationOrdering InformationTemperature Range Package TypeOutput VoltageNSC12V 15V ADJ Package Package Drawing −40˚C ≤T A ≤+125˚C24-Pin Surface Mount LM2577M-12LM2577M-15LM2577M-ADJ M24B SO 16-Pin Molded DIP LM2577N-12LM2577N-15LM2577N-ADJ N16A N 5-Lead Surface Mount LM2577S-12LM2577S-15LM2577S-ADJ TS5B TO-2635-Straight Leads LM2577T-12LM2577T-15LM2577T-ADJ T05A TO-2205-Bent Staggered LM2577T-12LM2577T-15LM2577T-ADJ T05DTO-220LeadsFlow LB03Flow LB03Flow LB03−55˚C ≤T A ≤+150˚C4-Pin TO-3LM1577K-12/883LM1577K-15/883LM1577K-ADJ/883K04ATO-3SIMPLE SWITCHER ®is a registered trademark of National Semiconductor Corporation.DS011468-1Note:Pin numbers shown are for TO-220(T)package.June 1999LM1577/LM2577Series SIMPLE SWITCHER Step-Up Voltage Regulator©1999National Semiconductor Corporation Absolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.Supply Voltage45V Output Switch Voltage65V Output Switch Current (Note 2) 6.0APower DissipationInternally Limited Storage Temperature Range −65˚C to +150˚CLead Temperature (Soldering,10sec.)260˚C Maximum Junction Temperature150˚CMinimum ESD Rating(C =100pF,R =1.5k Ω)2kVOperating RatingsSupply Voltage3.5V ≤V IN ≤40V Output Switch Voltage 0V ≤V SWITCH ≤60VOutput Switch CurrentI SWITCH ≤3.0A Junction Temperature Range LM1577−55˚C ≤T J ≤+150˚C LM2577−40˚C ≤T J ≤+125˚CElectrical Characteristics—LM1577-12,LM2577-12Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,and I SWITCH =0.LM1577-12LM2577-12Units SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)SYSTEM PARAMETERS Circuit of Figure 1(Note 6)V OUT Output Voltage V IN =5V to 10V12.0V I LOAD =100mA to 800mA11.60/11.4011.60/11.40V(min)(Note 3)12.40/12.6012.40/12.60V(max)Line Regulation V IN =3.5V to 10V 20mV I LOAD =300mA 50/10050/100mV(max)Load RegulationV IN =5V20mV I LOAD =100mA to 800mA 50/10050/100mV(max)ηEfficiencyV IN =5V,I LOAD =800mA 80%DEVICE PARAMETERSI SInput Supply CurrentV FEEDBACK =14V (Switch Off)7.5mA 10.0/14.010.0/14.0mA(max)I SWITCH =2.0A25mA V COMP =2.0V (Max Duty Cycle)50/8550/85mA(max)V UV Input SupplyI SWITCH =100mA2.90V Undervoltage Lockout2.70/2.65 2.70/2.65V(min)3.10/3.153.10/3.15V(max)f OOscillator FrequencyMeasured at Switch Pin 52kHz I SWITCH =100mA 48/4248/42kHz(min)56/6256/62kHz(max)V REFOutput Reference Measured at Feedback Pin V VoltageV IN =3.5V to 40V 1211.76/11.6411.76/11.64V(min)V COMP =1.0V 12.24/12.3612.24/12.36V(max)Output Reference V IN =3.5V to 40V7mVVoltage Line RegulatorR FB Feedback Pin Input 9.7k ΩResistance G MError Amp I COMP =−30µA to +30µA 370µmho TransconductanceV COMP =1.0V 225/145225/145µmho(min)515/615515/615µmho(max)A VOLError Amp V COMP =1.1V to 1.9V 80V/V Voltage GainR COMP =1.0M Ω50/2550/25V/V(min)(Note 7) 2Electrical Characteristics—LM1577-12,LM2577-12(Continued)Specifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,and I SWITCH=0.LM1577-12LM2577-12Units Symbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)DEVICE PARAMETERSError Amplifier Upper Limit 2.4VOutput Swing V FEEDBACK=10.0V 2.2/2.0 2.2/2.0V(min)Lower Limit0.3VV FEEDBACK=15.0V0.40/0.550.40/0.55V(max) Error Amplifier V FEEDBACK=10.0V to15.0V±200µAOutput Current V COMP=1.0V±130/±90±130/±90µA(min)±300/±400±300/±400µA(max) I SS Soft Start Current V FEEDBACK=10.0V 5.0µAV COMP=0V 2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)D Maximum Duty Cycle V COMP=1.5V95%I SWITCH=100mA93/9093/90%(min)SwitchTransconductance12.5A/VI L Switch Leakage V SWITCH=65V10µACurrent V FEEDBACK=15V(Switch Off)300/600300/600µA(max) V SAT Switch Saturation I SWITCH=2.0A0.5V Voltage V COMP=2.0V(Max Duty Cycle)0.7/0.90.7/0.9V(max)NPN Switch 4.5ACurrent Limit 3.7/3.0 3.7/3.0A(min)5.3/6.0 5.3/6.0A(max) Electrical Characteristics—LM1577-15,LM2577-15Specifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,and I SWITCH=0.LM1577-15LM2577-15Units Symbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)SYSTEM PARAMETERS Circuit of Figure2(Note6)V OUT Output Voltage V IN=5V to12V15.0VI LOAD=100mA to600mA14.50/14.2514.50/14.25V(min)(Note3)15.50/15.7515.50/15.75V(max)Line Regulation V IN=3.5V to12V2050/10050/100mVI LOAD=300mA mV(max)Load Regulation V IN=5V2050/10050/100mVI LOAD=100mA to600mA mV(max)ηEfficiency V IN=5V,I LOAD=600mA80% DEVICE PARAMETERSI S Input Supply Current V FEEDBACK=18.0V7.5mA(Switch Off)10.0/14.010.0/14.0mA(max)I SWITCH=2.0A25mAV COMP=2.0V50/8550/85mA(max)(Max Duty Cycle)V UV Input Supply I SWITCH=100mA 2.90V3Electrical Characteristics—LM1577-15,LM2577-15(Continued)Specifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,and I SWITCH=0.LM1577-15LM2577-15Units Symbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)DEVICE PARAMETERSUndervoltage 2.70/2.65 2.70/2.65V(min)Lockout 3.10/3.15 3.10/3.15V(max) f O Oscillator Frequency Measured at Switch Pin52kHzI SWITCH=100mA48/4248/42kHz(min)56/6256/62kHz(max) V REF Output Reference Measured at Feedback Pin V Voltage V IN=3.5V to40V1514.70/14.5514.70/14.55V(min)V COMP=1.0V15.30/15.4515.30/15.45V(max) Output Reference V IN=3.5V to40V10mVVoltage Line RegulationR FB Feedback Pin Input12.2kΩVoltage Line RegulatorG M Error Amp I COMP=−30µA to+30µA300µmhoTransconductance V COMP=1.0V170/110170/110µmho(min)420/500420/500µmho(max) A VOL Error Amp V COMP=1.1V to1.9V65V/VVoltage Gain R COMP=1.0MΩ40/2040/20V/V(min)(Note7)Error Amplifier Upper Limit 2.4VOutput Swing V FEEDBACK=12.0V 2.2/2.0 2.2/2.0V(min)Lower Limit0.3VV FEEDBACK=18.0V0.4/0.550.40/0.55V(max) Error Amp V FEEDBACK=12.0V to18.0V±200µAOutput Current V COMP=1.0V±130/±90±130/±90µA(min)±300/±400±300/±400µA(max) I SS Soft Start Current V FEEDBACK=12.0V 5.0µAV COMP=0V 2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)D Maximum Duty V COMP=1.5V95%Cycle I SWITCH=100mA93/9093/90%(min)12.5A/VSwitchI L Switch Leakage V SWITCH=65V10µACurrent V FEEDBACK=18.0V300/600300/600µA(max)(Switch Off)V SAT Switch Saturation I SWITCH=2.0A0.5V Voltage V COMP=2.0V0.7/0.90.7/0.9V(max)(Max Duty Cycle)NPN Switch V COMP=2.0V 4.3ACurrent Limit 3.7/3.0 3.7/3.0A(min)5.3/6.0 5.3/6.0A(max) 4Electrical Characteristics—LM1577-ADJ,LM2577-ADJSpecifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,V FEEDBACK=V REF,and I SWITCH=0.LM1577-ADJ LM2577-ADJ Units Symbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)SYSTEM PARAMETERS Circuit of Figure3(Note6)V OUT Output Voltage V IN=5V to10V12.0VI LOAD=100mA to800mA11.60/11.4011.60/11.40V(min)(Note3)12.40/12.6012.40/12.60V(max)∆V OUT/Line Regulation V IN=3.5V to10V20mV∆V IN I LOAD=300mA50/10050/100mV(max)∆V OUT/Load Regulation V IN=5V20mV∆I LOAD I LOAD=100mA to800mA50/10050/100mV(max)ηEfficiency V IN=5V,I LOAD=800mA80% DEVICE PARAMETERSI S Input Supply Current V FEEDBACK=1.5V(Switch Off)7.5mA10.0/14.010.0/14.0mA(max)I SWITCH=2.0A25mAV COMP=2.0V(Max Duty Cycle)50/8550/85mA(max)V UV Input Supply I SWITCH=100mA 2.90V Undervoltage Lockout 2.70/2.65 2.70/2.65V(min)3.10/3.15 3.10/3.15V(max)f O Oscillator Frequency Measured at Switch Pin52kHzI SWITCH=100mA48/4248/42kHz(min)56/6256/62kHz(max)V REF Reference Measured at Feedback Pin V Voltage V IN=3.5V to40V 1.230 1.214/1.206 1.214/1.206V(min)V COMP=1.0V 1.246/1.254 1.246/1.254V(max)∆V REF/Reference Voltage V IN=3.5V to40V0.5mV∆V IN Line RegulationI B Error Amp V COMP=1.0V100nAInput Bias Current300/800300/800nA(max)G M Error Amp I COMP=−30µA to+30µA3700µmhoTransconductance V COMP=1.0V2400/16002400/1600µmho(min)4800/58004800/5800µmho(max) A VOL Error Amp V COMP=1.1V to1.9V800V/VVoltage Gain R COMP=1.0MΩ(Note7)500/250500/250V/V(min)Error Amplifier Upper Limit 2.4VOutput Swing V FEEDBACK=1.0V 2.2/2.0 2.2/2.0V(min)Lower Limit0.3VV FEEDBACK=1.5V0.40/0.550.40/0.55V(max) Error Amp V FEEDBACK=1.0V to1.5V±200µAOutput Current V COMP=1.0V±130/±90±130/±90µA(min)±300/±400±300/±400µA(max)I SS Soft Start Current V FEEDBACK=1.0V 5.0µAV COMP=0V 2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)D Maximum Duty Cycle V COMP=1.5V95%I SWITCH=100mA93/9093/90%(min)∆I SWITCH/Switch12.5A/V∆V COMP Transconductance5Electrical Characteristics—LM1577-ADJ,LM2577-ADJ(Continued)Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,V FEEDBACK =V REF ,and I SWITCH =0.LM1577-ADJ LM2577-ADJUnits SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)DEVICE PARAMETERS I L Switch Leakage V SWITCH =65V10µA CurrentV FEEDBACK =1.5V (Switch Off)300/600300/600µA(max)V SATSwitch Saturation I SWITCH =2.0A0.5V Voltage V COMP =2.0V (Max Duty Cycle)0.7/0.90.7/0.9V(max)NPN Switch V COMP =2.0V4.3A Current Limit3.7/3.0 3.7/3.0A(min)5.3/6.05.3/6.0A(max)THERMAL PARAMETERS (All Versions)θJA Thermal ResistanceK Package,Junction to Ambient 35˚C/WθJC K Package,Junction to Case 1.5θJA T Package,Junction to Ambient 65θJC T Package,Junction to Case 2θJA N Package,Junction to 85Ambient (Note 8)θJA M Package,Junction 100to Ambient (Note 8)θJAS Package,Junction to 37Ambient (Note 9)Note 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating ratings indicate conditions 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:Due to timing considerations of the LM1577/LM2577current limit circuit,output current cannot be internally limited when the LM1577/LM2577is used as a step-up regulator.To prevent damage to the switch,its current must be externally limited to 6.0A.However,output current is internally limited when the LM1577/LM2577is used as a flyback or forward converter regulator in accordance to the Application Hints.Note 3:All limits guaranteed at room temperature (standard type face)and at temperature extremes (boldface type).All limits are used to calculate Outgoing Quality Level,and are 100%production tested.Note 4:A military RETS electrical test specification is available on request.At the time of printing,the LM1577K-12/883,LM1577K-15/883,and LM1577K-ADJ/883RETS specifications complied fully with the boldface limits in these columns.The LM1577K-12/883,LM1577K-15/883,and LM1577K-ADJ/883may also be procured to Standard Military Drawing specifications.Note 5:All limits guaranteed at room temperature (standard type face)and at temperature extremes (boldface type).All room temperature limits are 100%produc-tion tested.All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC)methods.Note 6:External components such as the diode,inductor,input and output capacitors can affect switching regulator performance.When the LM1577/LM2577is used as shown in the Test Circuit,system performance will be as specified by the system parameters.Note 7:A 1.0M Ωresistor is connected to the compensation pin (which is the error amplifier’s output)to ensure accuracy in measuring A VOL .In actual applications,this pin’s load resistance should be ≥10M Ω,resulting in A VOL that is typically twice the guaranteed minimum limit.Note 8:Junction to ambient thermal resistance with approximately 1square inch of pc board copper surrounding the leads.Additional copper area will lower thermal resistance further.See thermal model in “Switchers Made Simple”software.Note 9:If the TO-263package is used,the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the ing 0.5square inches of copper area,θJA is 50˚C/W;with 1square inch of copper area,θJA is 37˚C/W;and with 1.6or more square inches of copper area,θJA is 32˚C/W. 6Typical Performance CharacteristicsReference Voltagevs TemperatureDS011468-34Reference Voltagevs TemperatureDS011468-35Reference Voltagevs TemperatureDS011468-36∆Reference Voltagevs Supply VoltageDS011468-37∆Reference Voltagevs Supply VoltageDS011468-38∆Reference Voltagevs Supply VoltageDS011468-39Error Amp Transconductancevs TemperatureDS011468-40Error Amp Transconductancevs TemperatureDS011468-41Error Amp Transconductancevs TemperatureDS011468-42 7Typical Performance Characteristics(Continued)Error Amp Voltage Gain vs TemperatureDS011468-43Error Amp Voltage Gain vs TemperatureDS011468-44Error Amp Voltage Gain vs TemperatureDS011468-45Quiescent Current vs Temperature DS011468-46Quiescent Current vs Switch Current DS011468-47Current Limit vs TemperatureDS011468-48Current Limit Response Time vs Overdrive DS011468-49Switch Saturation Voltage vs Switch Current DS011468-50Switch Transconductance vs TemperatureDS011468-51 8Typical Performance Characteristics(Continued)Connection DiagramsFeedback Pin BiasCurrent vs TemperatureDS011468-52Oscillator Frequency vs TemperatureDS011468-53Maximum Power Dissipation (TO-263)(Note 9)DS011468-31Straight Leads 5-Lead TO-220(T)DS011468-4Top ViewOrder Number LM2577T-12,LM2577T-15,or LM2577T-ADJSee NS Package Number T05ABent,Staggered Leads 5-Lead TO-220(T)DS011468-5Top ViewOrder Number LM2577T-12Flow LB03,LM2577T-15Flow LB03,or LM2577T-ADJ Flow LB03See NS Package Number T05D9Connection Diagrams(Continued)16-Lead DIP(N)DS011468-6*No internal ConnectionTop ViewOrder Number LM2577N-12,LM2577N-15,or LM2577N-ADJSee NS Package Number N16A24-Lead Surface Mount(M)DS011468-7*No internal ConnectionTop ViewOrder Number LM2577M-12,LM2577M-15,or LM2577M-ADJSee NS Package Number M24BTO-263(S)5-Lead Surface-Mount PackageDS011468-32Top ViewDS011468-33Side ViewOrder Number LM2577S-12,LM2577S-15,or LM2577S-ADJSee NS Package Number TS5B4-Lead TO-3(K)DS011468-8Bottom ViewOrder Number LM1577K-12/883,LM1577K-15/883,or LM1577K-ADJ/883See NS Package Number K04A10LM1577-12,LM2577-12Test CircuitLM1577-15,LM2577-15Test CircuitLM1577-ADJ,LM2577-ADJ Test CircuitDS011468-30L =415-0930(AIE)D =any manufacturerC OUT =Sprague Type 673DElectrolytic 680µF,20VNote:Pin numbers shown are for TO-220(T)packageFIGURE 1.Circuit Used to Specify System Parameters for 12V VersionsDS011468-26L =415-0930(AIE)D =any manufacturerC OUT =Sprague Type 673DElectrolytic 680µF,20VNote:Pin numbers shown are for TO-220(T)packageFIGURE 2.Circuit Used to Specify System Parameters for 15V VersionsDS011468-9L =415-0930(AIE)D =any manufacturerC OUT =Sprague Type 673DElectrolytic 680µF,20VR1=48.7k in series with 511Ω(1%)R2=5.62k (1%)Note:Pin numbers shown are for TO-220(T)packageFIGURE 3.Circuit Used to Specify System Parameters for ADJ Versions11Application HintsDS011468-10Note:Pin numbers shown are for TO-220(T)package*Resistors are internal to LM1577/LM2577for12V and15V versions.FIGURE4.LM1577/LM2577Block Diagram and Boost Regulator Application 12ApplicationHints(Continued)STEP-UP (BOOST)REGULATORFigure 4shows the LM1577-ADJ/LM2577-ADJused as a Step-Up Regulator.This is a switching regulator used for producing an output voltage greater than the input supply voltage.The LM1577-12/LM2577-12and LM1577-15/LM2577-15can also be used for step-up regulators with 12V or 15V outputs (respectively),by tying the feedback pin di-rectly to the regulator output.A basic explanation of how it works is as follows.The LM1577/LM2577turns its output switch on and off at a fre-quency of 52kHz,and this creates energy in the inductor (L).When the NPN switch turns on,the inductor current charges up at a rate of V IN /L,storing current in the inductor.When the switch turns off,the lower end of the inductor flies above V IN ,discharging its current through diode (D)into the output ca-pacitor (C OUT )at a rate of (V OUT −V IN )/L.Thus,energy stored in the inductor during the switch on time is transferred to the output during the switch off time.The output voltage is controlled by the amount of energy transferred which,in turn,is controlled by modulating the peak inductor current.This is done by feeding back a portion of the output voltage to the error amp,which amplifies the difference between the feed-back voltage and a 1.230V reference.The error amp output voltage is compared to a voltage proportional to the switch current (i.e.,inductor current during the switch on time).The comparator terminates the switch on time when the two voltages are equal,thereby controlling the peak switch cur-rent to maintain a constant output voltage.Voltage and current waveforms for this circuit are shown in Figure 5,and formulas for calculating them are given in Fig-ure 6.STEP-UP REGULATOR DESIGN PROCEDUREThe following design procedure can be used to select the ap-propriate external components for the circuit in Figure 4,based on these system requirements.Given:V IN (min)=Minimum input supply voltage V OUT =Regulated output voltageI LOAD(max)=Maximum output load currentBefore proceeding any further,determine if the LM1577/LM2577can provide these values of V OUT and I LOAD(max)when operating with the minimum value of V IN .The upper limits for V OUT and I LOAD(max)are given by the following equations.V OUT ≤60V andV OUT ≤10x V IN(min)These limits must be greater than or equal to the values specified in this application.1.Inductor Selection (L)A.Voltage Options:1.For 12V or 15V outputDS011468-11FIGURE 5.Step-Up Regulator WaveformsDuty Cycle DAverage Inductor CurrentI IND(AVE)Application Hints(Continued)From Figure7(for12V output)or Figure8(for15Voutput),identify inductor code for region indicated byV IN(min)and I LOAD(max).The shaded region indicatesconditions for which the LM1577/LM2577output switchwould be operating beyond its switch current rating.Theminimum operating voltage for the LM1577/LM2577is3.5V.From here,proceed to step C.2.For Adjustable versionPreliminary calculations:The inductor selection is based on the calculation of thefollowing three parameters:D(max),the maximum switch duty cycle(0≤D≤0.9):where V F=0.5V for Schottky diodes and0.8V for fast recov-ery diodes(typically);E•T,the product of volts x time that charges the inductor:I IND,DC,the average inductor current under full load;B.Identify Inductor Value:1.From Figure9,identify the inductor code for the re-gion indicated by the intersection of E•T and I IND,DC.This code gives the inductor value in microhenries.TheL or H prefix signifies whether the inductor is rated for amaximum E•T of90V•µs(L)or250V•µs(H).2.If D<0.85,go on to step C.If D≥0.85,then calcu-late the minimum inductance needed to ensure theswitching regulator’s stability:If L MIN is smaller than the inductor value found in step B1,goon to step C.Otherwise,the inductor value found in step B1is too low;an appropriate inductor code should be obtainedfrom the graph as follows:1.Find the lowest value inductor that is greater than L MIN.2.Find where E•T intersects this inductor value to determineif it has an L or H prefix.If E•T intersects both the L and H re-gions,select the inductor with an H prefix.DS011468-27FIGURE7.LM2577-12Inductor Selection GuideDS011468-28FIGURE8.LM2577-15Inductor Selection Guide 14Application Hints(Continued)C.Select an inductor from the table of Figure10whichcross-references the inductor codes to the part numbers of three different plete specifica-tions for these inductors are available from the respec-tive manufacturers.The inductors listed in this table have the following characteristics:AIE:ferrite,pot-core inductors;Benefits of this type are low electro-magnetic interference(EMI),small physical size,and very low power dissipation(core loss).Be careful not to operate these inductors too far beyond their maximum ratings for E•T and peak current,as this will saturate the core.Pulse:powdered iron,toroid core inductors;Benefits are low EMI and ability to withstand E•T and peak current above rated value better than ferrite cores.Renco:ferrite,bobbin-core inductors;Benefits are low cost and best ability to withstand E•T and peak current above rated value.Be aware that these inductors gener-ate more EMI than the other types,and this may inter-fere with signals sensitive to noise.DS011468-12Note:These charts assume that the inductor ripple current inductor is approximately20%to30%of the average inductor current(when the regulator is underfull load).Greater ripple current causes higher peak switch currents and greater output ripple voltage;lower ripple current is achieved with larger-valueinductors.The factor of20to30%is chosen as a convenient balance between the two extremes.FIGURE9.LM1577-ADJ/LM2577-ADJ Inductor Selection Graph15Application Hints(Continued)pensation Network(R C,C C)and Output Capacitor(C OUT)SelectionR C and C C form a pole-zero compensation network that sta-bilizes the regulator.The values of R C and C C are mainly de-pendant on the regulator voltage gain,I LOAD(max),L andC OUT.The following procedure calculates values for R C,C C,and C OUT that ensure regulator stability.Be aware that thisprocedure doesn’t necessarily result in R C and C C that pro-vide optimum compensation.In order to guarantee optimumcompensation,one of the standard procedures for testingloop stability must be used,such as measuring V OUT tran-sient response when pulsing I LOAD(see Figure15).A.First,calculate the maximum value for R C.Select a resistor less than or equal to this value,and itshould also be no greater than3kΩ.B.Calculate the minimum value for C OUT using the followingtwo equations.The larger of these two values is the minimum value that en-sures stability.C.Calculate the minimum value of C C.The compensation capacitor is also part of the soft start cir-cuitry.When power to the regulator is turned on,the switchduty cycle is allowed to rise at a rate controlled by this ca-pacitor(with no control on the duty cycle,it would immedi-ately rise to90%,drawing huge currents from the inputpower supply).In order to operate properly,the soft start cir-cuit requires C C≥0.22µF.The value of the output filter capacitor is normally largeenough to require the use of aluminum electrolytic capaci-tors.Figure11lists several different types that are recom-mended for switching regulators,and the following param-eters are used to select the proper capacitor.Working Voltage(WVDC):Choose a capacitor with a work-ing voltage at least20%higher than the regulator output volt-age.Ripple Current:This is the maximum RMS value of currentthat charges the capacitor during each switching cycle.Forstep-up and flyback regulators,the formula for ripple currentisChoose a capacitor that is rated at least50%higher than thisvalue at52kHz.Equivalent Series Resistance(ESR):This is the primarycause of output ripple voltage,and it also affects the valuesof R C and C C needed to stabilize the regulator.As a result,the preceding calculations for C C and R C are only valid ifESR doesn’t exceed the maximum value specified by the fol-lowing equations.Select a capacitor with ESR,at52kHz,that is less than orequal to the lower value calculated.Most electrolytic capaci-tors specify ESR at120Hz which is15%to30%higher thanat52kHz.Also,be aware that ESR increases by a factor of2when operating at−20˚C.In general,low values of ESR are achieved by using largevalue capacitors(C≥470µF),and capacitors with highWVDC,or by paralleling smaller-value capacitors.Inductor Manufacturer’s Part NumberCode Schott Pulse RencoL4767126980PE-53112RL2442L6867126990PE-92114RL2443L10067127000PE-92108RL2444L150********PE-53113RL1954L22067127020PE-52626RL1953L33067127030PE-52627RL1952L47067127040PE-53114RL1951L68067127050PE-52629RL1950H150********PE-53115RL2445H22067127070PE-53116RL2446H33067127080PE-53117RL2447H47067127090PE-53118RL1961H68067127100PE-53119RL1960H100067127110PE-53120RL1959H150067127120PE-53121RL1958H220067127130PE-53122RL2448Schott Corp.,(612)475-11731000Parkers Lake Rd.,Wayzata,MN55391Pulse Engineering,(619)268-2400P.O.Box12235,San Diego,CA92112Renco Electronics Inc.,(516)586-556660Jeffryn Blvd.East,Deer Park,NY11729FIGURE10.Table of Standardized Inductors andManufacturer’s Part Numbers16。

LM2577中文资料

LM1577/LM2577SIMPLE SWITCHER ®Step-Up Voltage RegulatorGeneral DescriptionThe LM1577/LM2577are monolithic integrated circuits that provide all of the power and control functions for step-up (boost),flyback,and forward converter switching regulators.The device is available in three different output voltage versions:12V,15V,and adjustable.Requiring a minimum number of external components,these regulators are cost effective,and simple to use.Listed in this data sheet are a family of standard inductors and flyback transformers designed to work with these switching regula-tors.Included on the chip is a 3.0A NPN switch and its associated protection circuitry,consisting of current and thermal limiting,and undervoltage lockout.Other features include a 52kHz fixed-frequency oscillator that requires no external compo-nents,a soft start mode to reduce in-rush current during start-up,and current mode control for improved rejection of input voltage and output load transients.Featuresn Requires few external componentsn NPN output switches 3.0A,can stand off 65V n Wide input voltage range:3.5V to 40VnCurrent-mode operation for improved transient response,line regulation,and current limit n 52kHz internal oscillatorn Soft-start function reduces in-rush current during start-up n Output switch protected by current limit,under-voltage lockout,and thermal shutdown Typical Applicationsn Simple boost regulatorn Flyback and forward regulators n Multiple-output regulatorConnection DiagramsStraight Leads 5-Lead TO-220(T)Bent,Staggered Leads 5-Lead TO-220(T)01146804Top ViewOrder Number LM2577T-12,LM2577T-15,or LM2577T-ADJSee NS Package Number T05A 01146805Top ViewOrder Number LM2577T-12Flow LB03,LM2577T-15Flow LB03,or LM2577T-ADJ Flow LB03See NS Package Number T05DSIMPLE SWITCHER ®is a registered trademark of National Semiconductor Corporation.April 2005LM1577/LM2577SIMPLE SWITCHER Step-Up Voltage Regulator©2005National Semiconductor Corporation Connection Diagrams(Continued)16-Lead DIP (N)24-Lead Surface Mount (M)01146806*No internal ConnectionTop ViewOrder Number LM2577N-12,LM2577N-15,or LM2577N-ADJSee NS Package Number N16A01146807*No internal ConnectionTop ViewOrder Number LM2577M-12,LM2577M-15,or LM2577M-ADJSee NS Package Number M24BTO-263(S)5-Lead Surface-Mount Package01146832Top View01146833Side ViewOrder Number LM2577S-12,LM2577S-15,or LM2577S-ADJSee NS Package Number TS5B4-Lead TO-3(K)01146808Bottom ViewOrder Number LM1577K-12/883,LM1577K-15/883,or LM1577K-ADJ/883See NS Package Number K04AL M 1577/L M 2577 2Ordering InformationTemperature Range PackageTypeOutput Voltage NSC12V15V ADJ Package PackageDrawing−40˚C≤T A≤+125˚C24-Pin SurfaceMountLM2577M-12LM2577M-15LM2577M-ADJ M24B SO16-Pin Molded DIP LM2577N-12LM2577N-15LM2577N-ADJ N16A N5-Lead SurfaceMountLM2577S-12LM2577S-15LM2577S-ADJ TS5B TO-2635-Straight Leads LM2577T-12LM2577T-15LM2577T-ADJ T05A TO-2205-Bent Staggered LM2577T-12LM2577T-15LM2577T-ADJ T05D TO-220Leads Flow LB03Flow LB03Flow LB03−55˚C≤T A≤+150˚C4-Pin TO-3LM1577K-12/883LM1577K-15/883LM1577K-ADJ/883K04A TO-3 Typical Application01146801Note:Pin numbers shown are for TO-220(T)package.LM1577/LM25773Absolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.Supply Voltage 45V Output Switch Voltage 65V Output Switch Current (Note 2) 6.0APower DissipationInternally Limited Storage Temperature Range −65˚C to +150˚CLead Temperature (Soldering,10sec.)260˚C Maximum Junction Temperature150˚C Minimum ESD Rating (C =100pF,R =1.5k Ω)2kVOperating RatingsSupply Voltage 3.5V ≤V IN ≤40V Output Switch Voltage 0V ≤V SWITCH ≤60VOutput Switch Current I SWITCH ≤3.0AJunction Temperature Range LM1577−55˚C ≤T J ≤+150˚C LM2577−40˚C ≤T J ≤+125˚CElectrical Characteristics—LM1577-12,LM2577-12Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,and I SWITCH =0.LM1577-12LM2577-12Units SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)SYSTEM PARAMETERS Circuit of Figure 1(Note 6)V OUTOutput VoltageV IN =5V to 10V12.0V I LOAD =100mA to 800mA 11.60/11.4011.60/11.40V(min)(Note 3)12.40/12.6012.40/12.60V(max)Line RegulationV IN =3.5V to 10V 20mV I LOAD =300mA50/10050/100mV(max)Load RegulationV IN =5V20mV I LOAD =100mA to 800mA50/10050/100mV(max)ηEfficiencyV IN =5V,I LOAD =800mA 80%DEVICE PARAMETERSI SInput Supply CurrentV FEEDBACK =14V (Switch Off)7.5mA 10.0/14.010.0/14.0mA(max)I SWITCH =2.0A25mA V COMP =2.0V (Max Duty Cycle)50/8550/85mA(max)V UVInput SupplyI SWITCH =100mA2.90V Undervoltage Lockout2.70/2.65 2.70/2.65V(min)3.10/3.153.10/3.15V(max)f OOscillator FrequencyMeasured at Switch Pin 52kHz I SWITCH =100mA48/4248/42kHz(min)56/6256/62kHz(max)V REFOutput Reference Measured at Feedback Pin V VoltageV IN =3.5V to 40V 1211.76/11.6411.76/11.64V(min)V COMP =1.0V 12.24/12.3612.24/12.36V(max)Output Reference V IN =3.5V to 40V7mVVoltage Line RegulatorR FB Feedback Pin Input 9.7k ΩResistance G MError Amp I COMP =−30µA to +30µA 370µmho TransconductanceV COMP =1.0V225/145225/145µmho(min)515/615515/615µmho(max)L M 1577/L M 2577 4Electrical Characteristics—LM1577-12,LM2577-12(Continued)Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,and I SWITCH =0.LM1577-12LM2577-12Units SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)DEVICE PARAMETERS A VOLError Amp V COMP =1.1V to 1.9V 80V/VVoltage Gain R COMP =1.0M Ω50/2550/25V/V(min)(Note 7)Error Amplifier Upper Limit 2.4V Output SwingV FEEDBACK =10.0V 2.2/2.02.2/2.0V(min)Lower Limit 0.3V V FEEDBACK =15.0V0.40/0.550.40/0.55V(max)Error Amplifier V FEEDBACK =10.0V to 15.0V ±200µA Output CurrentV COMP =1.0V ±130/±90±130/±90µA(min)±300/±400±300/±400µA(max)I SSSoft Start CurrentV FEEDBACK =10.0V 5.0µAV COMP =0V2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)DMaximum Duty Cycle V COMP =1.5V 95%I SWITCH =100mA93/9093/90%(min)SwitchTransconductance12.5A/V I L Switch Leakage V SWITCH =65V10µA CurrentV FEEDBACK =15V (Switch Off)300/600300/600µA(max)V SATSwitch Saturation I SWITCH =2.0A0.5V Voltage V COMP =2.0V (Max Duty Cycle)0.7/0.90.7/0.9V(max)NPN Switch 4.5A Current Limit3.7/3.0 3.7/3.0A(min)5.3/6.05.3/6.0A(max)Electrical Characteristics—LM1577-15,LM2577-15Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,and I SWITCH =0.LM1577-15LM2577-15Units SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)SYSTEM PARAMETERS Circuit of Figure 2(Note 6)V OUTOutput VoltageV IN =5V to 12V15.0V I LOAD =100mA to 600mA 14.50/14.2514.50/14.25V(min)(Note 3)15.50/15.7515.50/15.75V(max)Line RegulationV IN =3.5V to 12V 2050/10050/100mV I LOAD =300mAmV(max)Load RegulationV IN =5V2050/10050/100mV I LOAD =100mA to 600mAmV(max)ηEfficiencyV IN =5V,I LOAD =600mA80%LM1577/LM25775Electrical Characteristics—LM1577-15,LM2577-15(Continued)Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,and I SWITCH =0.LM1577-15LM2577-15Units SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)DEVICE PARAMETERS I SInput Supply CurrentV FEEDBACK =18.0V 7.5mA(Switch Off)10.0/14.010.0/14.0mA(max)I SWITCH =2.0A 25mA V COMP =2.0V 50/8550/85mA(max)(Max Duty Cycle)V UVInput Supply I SWITCH =100mA2.90V Undervoltage 2.70/2.65 2.70/2.65V(min)Lockout3.10/3.153.10/3.15V(max)f OOscillator FrequencyMeasured at Switch Pin 52kHz I SWITCH =100mA48/4248/42kHz(min)56/6256/62kHz(max)V REFOutput Reference Measured at Feedback Pin VVoltageV IN =3.5V to 40V 1514.70/14.5514.70/14.55V(min)V COMP =1.0V 15.30/15.4515.30/15.45V(max)Output Reference V IN =3.5V to 40V10mV Voltage Line RegulationR FB Feedback Pin Input 12.2k ΩVoltage Line Regulator G MError Amp I COMP =−30µA to +30µA 300µmho TransconductanceV COMP =1.0V 170/110170/110µmho(min)420/500420/500µmho(max)A VOLError Amp V COMP =1.1V to 1.9V 65V/V Voltage GainR COMP =1.0M Ω40/2040/20V/V(min)(Note 7)Error Amplifier Upper Limit 2.4V Output SwingV FEEDBACK =12.0V 2.2/2.02.2/2.0V(min)Lower Limit 0.3V V FEEDBACK =18.0V0.4/0.550.40/0.55V(max)Error Amp V FEEDBACK =12.0V to 18.0V ±200µA Output CurrentV COMP =1.0V ±130/±90±130/±90µA(min)±300/±400±300/±400µA(max)I SSSoft Start CurrentV FEEDBACK =12.0V 5.0µA V COMP =0V2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)D Maximum Duty V COMP =1.5V 95%CycleI SWITCH =100mA93/9093/90%(min)SwitchTransconductance12.5A/VI LSwitch Leakage V SWITCH =65V 10µA CurrentV FEEDBACK =18.0V 300/600300/600µA(max)(Switch Off)V SATSwitch Saturation I SWITCH =2.0A 0.5V VoltageV COMP =2.0V 0.7/0.90.7/0.9V(max)(Max Duty Cycle)L M 1577/L M 2577 6LM1577/LM2577 Electrical Characteristics—LM1577-15,LM2577-15(Continued)Specifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,and I SWITCH=0.LM1577-15LM2577-15Units Symbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)DEVICE PARAMETERSNPN Switch V COMP=2.0V 4.3ACurrent Limit 3.7/3.0 3.7/3.0A(min)5.3/6.0 5.3/6.0A(max) Electrical Characteristics—LM1577-ADJ,LM2577-ADJSpecifications with standard type face are for T J=25˚C,and those in bold type face apply over full Operating Temperature Range.Unless otherwise specified,V IN=5V,V FEEDBACK=V REF,and I SWITCH=0.LM1577-ADJ LM2577-ADJ UnitsSymbol Parameter Conditions Typical Limit Limit(Limits)(Notes3,4)(Note5)SYSTEM PARAMETERS Circuit of Figure3(Note6)V OUT Output Voltage V IN=5V to10V12.0VI LOAD=100mA to800mA11.60/11.4011.60/11.40V(min)(Note3)12.40/12.6012.40/12.60V(max)∆V OUT/Line Regulation V IN=3.5V to10V20mV∆V IN I LOAD=300mA50/10050/100mV(max)∆V OUT/Load Regulation V IN=5V20mV∆I LOAD I LOAD=100mA to800mA50/10050/100mV(max)ηEfficiency V IN=5V,I LOAD=800mA80%DEVICE PARAMETERSI S Input Supply Current V FEEDBACK=1.5V(Switch Off)7.5mA10.0/14.010.0/14.0mA(max)I SWITCH=2.0A25mAV COMP=2.0V(Max Duty Cycle)50/8550/85mA(max)V UV Input Supply I SWITCH=100mA 2.90V Undervoltage Lockout 2.70/2.65 2.70/2.65V(min)3.10/3.15 3.10/3.15V(max)f O Oscillator Frequency Measured at Switch Pin52kHzI SWITCH=100mA48/4248/42kHz(min)56/6256/62kHz(max)V REF Reference Measured at Feedback Pin V Voltage V IN=3.5V to40V 1.230 1.214/1.206 1.214/1.206V(min)V COMP=1.0V 1.246/1.254 1.246/1.254V(max)∆V REF/Reference Voltage V IN=3.5V to40V0.5mV∆V IN Line RegulationI B Error Amp V COMP=1.0V100nAInput Bias Current300/800300/800nA(max)G M Error Amp I COMP=−30µA to+30µA3700µmhoTransconductance V COMP=1.0V2400/16002400/1600µmho(min)4800/58004800/5800µmho(max)A VOL Error Amp V COMP=1.1V to1.9V800V/VVoltage Gain R COMP=1.0MΩ(Note7)500/250500/250V/V(min)7Electrical Characteristics—LM1577-ADJ,LM2577-ADJ(Continued)Specifications with standard type face are for T J =25˚C,and those in bold type face apply over full Operating Temperature Range .Unless otherwise specified,V IN =5V,V FEEDBACK =V REF ,and I SWITCH =0.LM1577-ADJ LM2577-ADJUnits SymbolParameterConditionsTypicalLimit Limit (Limits)(Notes 3,4)(Note 5)DEVICE PARAMETERSError Amplifier Upper Limit 2.4VOutput SwingV FEEDBACK =1.0V 2.2/2.02.2/2.0V(min)Lower Limit 0.3V V FEEDBACK =1.5V0.40/0.550.40/0.55V(max)Error Amp V FEEDBACK =1.0V to 1.5V ±200µA Output CurrentV COMP =1.0V ±130/±90±130/±90µA(min)±300/±400±300/±400µA(max)I SSSoft Start CurrentV FEEDBACK =1.0V 5.0µAV COMP =0V2.5/1.5 2.5/1.5µA(min)7.5/9.57.5/9.5µA(max)D Maximum Duty Cycle V COMP =1.5V 95%I SWITCH =100mA93/9093/90%(min)∆I SWITCH /Switch12.5A/V ∆V COMP Transconductance I L Switch Leakage V SWITCH =65V10µA CurrentV FEEDBACK =1.5V (Switch Off)300/600300/600µA(max)V SATSwitch Saturation I SWITCH =2.0A0.5V Voltage V COMP =2.0V (Max Duty Cycle)0.7/0.90.7/0.9V(max)NPN Switch V COMP =2.0V4.3A Current Limit3.7/3.0 3.7/3.0A(min)5.3/6.05.3/6.0A(max)THERMAL PARAMETERS (All Versions)θJA Thermal ResistanceK Package,Junction to Ambient 35˚C/WθJC K Package,Junction to Case 1.5θJA T Package,Junction to Ambient 65θJC T Package,Junction to Case 2θJA N Package,Junction to 85Ambient (Note 8)θJA M Package,Junction 100to Ambient (Note 8)θJAS Package,Junction to 37Ambient (Note 9)Note 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating ratings indicate conditions 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:Due to timing considerations of the LM1577/LM2577current limit circuit,output current cannot be internally limited when the LM1577/LM2577is used as a step-up regulator.To prevent damage to the switch,its current must be externally limited to 6.0A.However,output current is internally limited when the LM1577/LM2577is used as a flyback or forward converter regulator in accordance to the Application Hints.Note 3:All limits guaranteed at room temperature (standard type face)and at temperature extremes (boldface type).All limits are used to calculate Outgoing Quality Level,and are 100%production tested.Note 4:A military RETS electrical test specification is available on request.At the time of printing,the LM1577K-12/883,LM1577K-15/883,and LM1577K-ADJ/883RETS specifications complied fully with the boldface limits in these columns.The LM1577K-12/883,LM1577K-15/883,and LM1577K-ADJ/883may also be procured to Standard Military Drawing specifications.Note 5:All limits guaranteed at room temperature (standard type face)and at temperature extremes (boldface type).All room temperature limits are 100%production tested.All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC)methods.Note 6:External components such as the diode,inductor,input and output capacitors can affect switching regulator performance.When the LM1577/LM2577is used as shown in the Test Circuit,system performance will be as specified by the system parameters.Note 7:A 1.0M Ωresistor is connected to the compensation pin (which is the error amplifier’s output)to ensure accuracy in measuring A VOL .In actual applications,this pin’s load resistance should be ≥10M Ω,resulting in A VOL that is typically twice the guaranteed minimum limit.L M 1577/L M 2577 8Electrical Characteristics—LM1577-ADJ,LM2577-ADJ(Continued)Note8:Junction to ambient thermal resistance with approximately1square inch of pc board copper surrounding the leads.Additional copper area will lower thermal resistance further.See thermal model in“Switchers Made Simple”software.Note9:If the TO-263package is used,the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the ing 0.5square inches of copper area,θJA is50˚C/W;with1square inch of copper area,θJA is37˚C/W;and with1.6or more square inches of copper area,θJA is32˚C/W. Typical Performance CharacteristicsReference Voltage vs TemperatureReference Voltagevs Temperature 0114683401146835Reference Voltage vs Temperature∆Reference Voltagevs Supply Voltage 0114683601146837∆Reference Voltage vs Supply Voltage∆Reference Voltagevs Supply Voltage0114683801146839LM1577/LM25779Typical Performance Characteristics(Continued)Error Amp Transconductancevs TemperatureError Amp Transconductancevs Temperature0114684001146841Error Amp Transconductancevs Temperature Error Amp Voltage Gain vs Temperature0114684201146843Error Amp Voltage Gain vs Temperature Error Amp Voltage Gain vs Temperature0114684401146845L M 1577/L M 2577 10Typical Performance Characteristics(Continued)Quiescent Current vs TemperatureQuiescent Current vs Switch Current0114684601146847Current Limit vs Temperature Current Limit Response Time vs Overdrive0114684801146849Switch Saturation Voltagevs Switch Current Switch Transconductancevs Temperature0114685001146851LM1577/LM2577Typical Performance Characteristics(Continued)Feedback Pin Bias Current vs TemperatureOscillator Frequency vs Temperature0114685201146853Maximum Power Dissipation(TO-263)(Note 9)01146831L M 1577/L M 2577LM1577-12,LM2577-12Test CircuitLM1577-15,LM2577-15Test Circuit 01146830L=415-0930(AIE)D=any manufacturerC OUT=Sprague Type673DElectrolytic680µF,20VNote:Pin numbers shown are for TO-220(T)packageFIGURE1.Circuit Used to Specify System Parameters for12V Versions01146826 L=415-0930(AIE)D=any manufacturerC OUT=Sprague Type673DElectrolytic680µF,20VNote:Pin numbers shown are for TO-220(T)packageFIGURE2.Circuit Used to Specify System Parameters for15V Versions LM1577/LM2577LM1577-ADJ,LM2577-ADJ Test CircuitApplication Hints01146809L =415-0930(AIE)D =any manufacturer C OUT =Sprague Type 673DElectrolytic 680µF,20VR1=48.7k in series with 511Ω(1%)R2=5.62k (1%)Note:Pin numbers shown are for TO-220(T)packageFIGURE 3.Circuit Used to Specify System Parameters for ADJ Versions01146810Note:Pin numbers shown are for TO-220(T)package*Resistors are internal to LM1577/LM2577for 12V and 15V versions.FIGURE 4.LM1577/LM2577Block Diagram and Boost Regulator ApplicationL M 1577/L M 2577Application Hints(Continued)STEP-UP (BOOST)REGULATORFigure 4shows the LM1577-ADJ/LM2577-ADJ used as a Step-Up Regulator.This is a switching regulator used for producing an output voltage greater than the input supply voltage.The LM1577-12/LM2577-12and LM1577-15/LM2577-15can also be used for step-up regulators with 12V or 15V outputs (respectively),by tying the feedback pin directly to the regulator output.A basic explanation of how it works is as follows.The LM1577/LM2577turns its output switch on and off at a frequency of 52kHz,and this creates energy in the inductor (L).When the NPN switch turns on,the inductor current charges up at a rate of V IN /L,storing current in the inductor.When the switch turns off,the lower end of the inductor flies above V IN ,discharging its current through diode (D)into the output capacitor (C OUT )at a rate of (V OUT −V IN )/L.Thus,energy stored in the inductor during the switch on time is transferred to the output during the switch off time.The output voltage is controlled by the amount of energy trans-ferred which,in turn,is controlled by modulating the peak inductor current.This is done by feeding back a portion of the output voltage to the error amp,which amplifies the difference between the feedback voltage and a 1.230V ref-erence.The error amp output voltage is compared to a voltage proportional to the switch current (i.e.,inductor cur-rent during the switch on time).The comparator terminates the switch on time when the two voltages are equal,thereby controlling the peak switch cur-rent to maintain a constant output voltage.Voltage and current waveforms for this circuit are shown in Figure 5,and formulas for calculating them are given in Figure 6.STEP-UP REGULATOR DESIGN PROCEDUREThe following design procedure can be used to select the appropriate external components for the circuit in Figure 4,based on these system requirements.Given:V IN (min)=Minimum input supply voltage V OUT =Regulated output voltageI LOAD(max)=Maximum output load current Before proceeding any further,determine if the LM1577/LM2577can provide these values of V OUT and I LOAD(max)when operating with the minimum value of V IN .The upper limits for V OUT and I LOAD(max)are given by the following equations.V OUT ≤60Vand V OUT ≤10x V IN(min)These limits must be greater than or equal to the values specified in this application.1.Inductor Selection (L)A.Voltage Options:1.For 12V or 15V outputFrom Figure 7(for 12V output)or Figure 8(for 15V output),identify inductor code for region indicated by V IN (min)and I LOAD (max).The shaded region indicates con-01146811FIGURE 5.Step-Up Regulator WaveformsDuty Cycle DAverage Inductor Current I IND(AVE)InductorCurrent Ripple ∆I IND Peak Inductor Current I IND(PK)Peak Switch Current I SW(PK)SwitchVoltage When Off V SW(OFF)V OUT +V FDiode Reverse Voltage V R V OUT −V SATAverageDiode Current I D(AVE)I LOADPeak Diode Current I D(PK)PowerDissipation of LM1577/2577P DV F =Forward Biased Diode Voltage I LOAD =Output Load CurrentFIGURE 6.Step-Up Regulator FormulasLM1577/LM2577Application Hints(Continued)ditions for which the LM1577/LM2577output switchwould be operating beyond its switch current rating.Theminimum operating voltage for the LM1577/LM2577is3.5V.From here,proceed to step C.2.For Adjustable versionPreliminary calculations:The inductor selection is based on the calculation of thefollowing three parameters:D(max),the maximum switch duty cycle(0≤D≤0.9):where V F=0.5V for Schottky diodes and0.8V for fastrecovery diodes(typically);E•T,the product of volts x time that charges the inductor:I IND,DC,the average inductor current under full load;B.Identify Inductor Value:1.From Figure9,identify the inductor code for theregion indicated by the intersection of E•T and I IND,DC.This code gives the inductor value in microhenries.TheL or H prefix signifies whether the inductor is rated for amaximum E•T of90V•µs(L)or250V•µs(H).2.If D<0.85,go on to step C.If D≥0.85,then calculatethe minimum inductance needed to ensure the switchingregulator’s stability:If L MIN is smaller than the inductor value found in step B1,goon to step C.Otherwise,the inductor value found in step B1is too low;an appropriate inductor code should be obtainedfrom the graph as follows:1.Find the lowest value inductor that is greater than L MIN.2.Find where E•T intersects this inductor value to determineif it has an L or H prefix.If E•T intersects both the L and Hregions,select the inductor with an H prefix.01146827FIGURE7.LM2577-12Inductor Selection Guide01146828FIGURE8.LM2577-15Inductor Selection GuideLM1577/LM2577Application Hints(Continued)C.Select an inductor from the table of Figure10whichcross-references the inductor codes to the part numbers of three different plete specifications for these inductors are available from the respective manufacturers.The inductors listed in this table have the following characteristics:AIE:ferrite,pot-core inductors;Benefits of this type are low electro-magnetic interference(EMI),small physical size,and very low power dissipation(core loss).Be careful not to operate these inductors too far beyond their maximum ratings for E•T and peak current,as this will saturate the core.Pulse:powdered iron,toroid core inductors;Benefits are low EMI and ability to withstand E•T and peak current above rated value better than ferrite cores.Renco:ferrite,bobbin-core inductors;Benefits are low cost and best ability to withstand E•T and peak current above rated value.Be aware that these inductors gener-ate more EMI than the other types,and this may interfere with signals sensitive to noise.01146812Note:These charts assume that the inductor ripple current inductor is approximately20%to30%of the average inductor current(when the regulator is under full load).Greater ripple current causes higher peak switch currents and greater output ripple voltage;lower ripple current is achieved with larger-value inductors.The factor of20to30%is chosen as a convenient balance between the two extremes.FIGURE9.LM1577-ADJ/LM2577-ADJ Inductor Selection Graph LM1577/LM2577Application Hints(Continued)pensation Network (R C ,C C )and Output Capacitor (C OUT )SelectionR C and C C form a pole-zero compensation network that stabilizes the regulator.The values of R C and C C are mainly dependant on the regulator voltage gain,I LOAD(max),L and C OUT .The following procedure calculates values for R C ,C C ,and C OUT that ensure regulator stability.Be aware that this procedure doesn’t necessarily result in R C and C C that pro-vide optimum compensation.In order to guarantee optimum compensation,one of the standard procedures for testing loop stability must be used,such as measuring V OUT tran-sient response when pulsing I LOAD (see Figure 15).A.First,calculate the maximum value for R C .Select a resistor less than or equal to this value,and it should also be no greater than 3k Ω.B.Calculate the minimum value for C OUT using the following two equations.The larger of these two values is the minimum value that ensures stability.C.Calculate the minimum value of C C .The compensation capacitor is also part of the soft start circuitry.When power to the regulator is turned on,the switch duty cycle is allowed to rise at a rate controlled by this capacitor (with no control on the duty cycle,it would imme-diately rise to 90%,drawing huge currents from the input power supply).In order to operate properly,the soft start circuit requires C C ≥0.22µF.The value of the output filter capacitor is normally large enough to require the use of aluminum electrolytic capaci-tors.Figure 11lists several different types that are recom-mended for switching regulators,and the following param-eters are used to select the proper capacitor.Working Voltage (WVDC):Choose a capacitor with a work-ing voltage at least 20%higher than the regulator output voltage.Ripple Current:This is the maximum RMS value of current that charges the capacitor during each switching cycle.For step-up and flyback regulators,the formula for ripple current isChoose a capacitor that is rated at least 50%higher than this value at 52kHz.Equivalent Series Resistance (ESR):This is the primary cause of output ripple voltage,and it also affects the values of R C and C C needed to stabilize the regulator.As a result,the preceding calculations for C C and R C are only valid if ESR doesn’t exceed the maximum value specified by the following equations.Select a capacitor with ESR,at 52kHz,that is less than or equal to the lower value calculated.Most electrolytic capaci-tors specify ESR at 120Hz which is 15%to 30%higher than at 52kHz.Also,be aware that ESR increases by a factor of 2when operating at −20˚C.In general,low values of ESR are achieved by using large value capacitors (C ≥470µF),and capacitors with high WVDC,or by paralleling smaller-value capacitors.Inductor Manufacturer’s Part Number Code Schott Pulse Renco L4767126980PE -53112RL2442L6867126990PE -92114RL2443L10067127000PE -92108RL2444L150********PE -53113RL1954L22067127020PE -52626RL1953L33067127030PE -52627RL1952L47067127040PE -53114RL1951L68067127050PE -52629RL1950H150********PE -53115RL2445H22067127070PE -53116RL2446H33067127080PE -53117RL2447H47067127090PE -53118RL1961H68067127100PE -53119RL1960H100067127110PE -53120RL1959H150067127120PE -53121RL1958H220067127130PE -53122RL2448Schott Corp.,(612)475-11731000Parkers Lake Rd.,Wayzata,MN 55391Pulse Engineering ,(619)268-2400P .O.Box 12235,San Diego,CA 92112Renco Electronics Inc.,(516)586-556660Jeffryn Blvd.East,Deer Park,NY 11729FIGURE 10.Table of Standardized Inductors andManufacturer’s Part Numbers L M 1577/L M 2577。

模拟电子技术基础-lm2576电源转换电路

课程综合设计课程名称：《模拟电子技术基础》实验名称：《LM2576电源转换电路》学院：应用科技学院专业：电子信息工程年级：2012级学号：姓名：一、设计意义及实现功能:LM2576系列是美国国家半导体公司生产的3A电流输出降压开关型集成稳压电路，它内含固定频率振荡器(52kHz)和基准稳压器(1.23V)，并具有完善的保护电路，包括电流限制及热关断电路等，利用该器件只需极少的外围器件便可构成高效稳压电路。

各系列产品均提供有3.3V(-3.3)、5V(-5.0)、12V(-12)、15V(-15)及可调(-ADJ)等多个电压档次产品。

二、LM2576的内部组成:LM2576的内部框图如图所示LM2576内部包含52kHz振荡器、1.23V基准稳压电路、热关断电路、电流限制电路、放大器、比较器及内部稳压电路等。

为了产生不同的输出电压，通常将比较器的负端接基准电压（1.23V），正端接分压电阻网络，这样可根据输出电压的不同选定不同的阻值，其中R1=1kΩ（可调-ADJ时开路），R2分别为1.7kΩ（3.3V）、3.1kΩ（5V）、8.84kΩ（12V）、11.3 kΩ（15V）和0（-ADJ），上述电阻依据型号不同已在芯片内部做了精确调整，因而无需使用者考虑。

将输出电压分压电阻网络的输出同内部基准稳压值1.23V进行比较，若电压有偏差，则可用放大器控制内部振荡器的输出占空比，从而使输出电压保持稳定。

管脚定义LM2576ADJ各脚功能如下：1）VIN—输入电压端，为减小输入瞬态电压和给调节器提供开关电流，此管脚应接旁路电容CIN；2）OUTPUT—稳压输出端，输出高电压为（VIN－VSAT），输出低电压为-0.5V。

3）GND—电路地；4）FEEDBACK—反馈端；5）ON/OFF—控制端，高电平有效，待机静态电流仅为75µA。

①脚为直流电压输入端，输入电压最高为45 V。

若由低压交流整流供电，为了避免空载时电压超出45 V，交流输入电压应不高于32 V。

LM2576芯片

特点 LM2576■ 3.3V,5V,12V,15V 的固定输出电压和可调输出■ 只需要 4 个外接元件版本■ 52KHz 固定内置频率振荡器■ 可调版本输出电压范围：1.23V～37V(HV 版本■ TTL 电平关断，低功耗备用模式到57V)±4% ■ 高效率■ 3A 的输出电流■ 过热关断和限流保护■ 宽电源输入范围，输入电压可达 40V(HV 版本■ 使用易提供的标准电感器为60V)应用■ 简单高效率降压(Buck)调节器■ 卡式开关调节器■ 高效率的线性前级转换器■ 正电压到负电压转换器（Buck-Boost）概述HYM2576 系列调节器是具有 3A 电流负载能力的单片降压转换(Buck)开关型集成电路，有着极好的线性和负载调节特性。

HYM2576系列器件包括固定的 3.3V、5V、12V、15V输出版本和可调输出版本。

HYM2576 使用起来非常简单，仅需几个外接元件，并且集成了内部频率补偿和一个固定频率振荡器。

HYM2576 系列是三端线性调节器的高效替代产品。

它可以最大限度的减小散热片的尺寸，在某些情况下可以不加散热片。

标准的系列电感可以从很多不同的厂家购买，这些特性最大程度的简化了开关电源的设计。

在特定输入和输出负载的条件下，HYM2576的输出可以保证±4%的精度容差，以及±10%的内部振荡频率容差。

HYM2576同时提供外部关断功能，具有50µA（典型）的静态电流。

HYM2596还具有循环限流和过温关断特性，具备完善的保护功能。

方框图和管脚功能3.3V R2=1.7K 5V R2=3.1K 12V R2=8.84K 15V R2=11.3K ADJ. Version R1: Open, R2=0Ω图 1.内部方框图- 1 -HYM2576 管脚图图 2.管脚图HYM2576 电特性HYM2576-3.3,HYM2576HV-3.3电特性HYM2576-3.3 符号参数条件HYM2576HV-3.3 单位最小典型最大系统参数（注释3）测试电路如图3V OUT 输出电压V IN=12V,I LOAD=0.5A(如图 3) 3.234 3.3 3.366 V V OUT 输出电压6V≤V IN≤40V,0.5A≤I LOAD≤3A 3.168/ 3.3 3.432/ V HYM2576 (如图 3) 3.135 3.465 V OUT 输出电压6V≤V IN≤60V,0.5A≤I LOAD≤3A 3.168/ 3.3 3.450/ V HYM2576HV （如图3） 3.135 3.482 η效率V IN=12V,I LOAD=3A 75 % HYM2576-5.0,HYM2576HV-5.0电特性HYM2576-5.0 符号参数条件HYM2576HV-5.0 单位最小典型最大系统参数（注释3）测试电路如图3V OUT 输出电压V IN=12V,ILOAD=0.5A(如图 3) 4.900 5.0 5.100 V V OUT 输出电压8V≤V IN≤40V,0.5A≤I LOAD≤3A 4.800/ 5.0 5.200/ V HYM2576 (如图 3) 4.750 5.250 V OUT 输出电压8V≤V IN≤60V,0.5A≤I LOAD≤3A 4.800/ 5.0 5.225/ V HYM2576HV （如图3） 4.750 5.275 η效率V IN=12V,I LOAD=3A 77 % HYM2576-12,HYM2576HV-12电特性HYM2576-12 符号参数条件HYM2576HV-12 单位最小典型最大系统参数（注释3）测试电路如图3V OUT 输出电压V IN=25V,I LOAD=0.5A(如图 3) 11.76 12 12.24 V V OUT 输出电压15V≤V IN≤40V,0.5A≤I LOAD≤3A11.52/ 12 12.48/ V HYM2576 (如图 3) 11.40 12.60 V OUT 输出电压15V≤V IN≤60V,0.5A≤I LOAD≤3A11.52/ 12 12.54/ V HYM2576HV （如图3）11.40 12.66 η效率V IN=15V,I LOAD=3A 88 % HYM2576-15,HYM2576HV-15电特性HYM2576-15 符号参数条件HYM2576HV-15 单位最小典型最大系统参数（注释3）测试电路如图3- 3 -。

开关型稳压芯片LM2576中文资料

启闭型稳压芯片LM2576华文资料之阳早格格创做LM2576系列启闭稳压集成电路是线性三端稳压器件(如78xx系列端稳压集成电路)的代替品，它具备稳当的处事本能、较下的处事效用战较强的输出电流启动本领，进而为MCU的宁静、稳当处事提供了强有力的包管.LM2576简介LM2576系列是好国国家半导体公司死产的3A电流输出降压启闭型集成稳压电路，它内含牢固频次振荡器(52kHz)战基准稳压器(1.23V)，并具备完备的呵护电路，包罗电流节造及热闭断电路等，利用该器件只需极少的中围器件即可形成下效稳压电路.LM2576系列包罗LM2576(最下输进电压40V)及LM2576HV(最下输进电压60V)二个系列.各系列产品均提供有3.3V(-3.3)、5V(-5.0)、12V(-12)、15V(-15)及可调(-ADJ)等多个电压档次产品.别的，该芯片还提供了处事状态的中部统造引足.LM2576系列启闭稳压集成电路的主要个性如下[2]：●最大输出电流：3A;●最下输进电压：LM2576为40V，LM2576HV为60V;●输出电压：3.3V、5V、12V、15V战ADJ(可调)等可选;●振东频次：52kHz;●变换效用：75%～88%(分歧电压输出时的效用分歧);●统造办法：PWM;●处事温度范畴：-40℃～ +125℃●处事模式：矮功耗/仄常二种模式可中部统造;●处事模式统造：TTL电仄兼容;●所需中部元件：仅四个(没有成调)或者六个(可调);●器件呵护：热闭断及电流节造;●启拆形式：TO-220或者TO-263.LM2576的里面框图如图1所示，该框图的引足定义对付应于五足TO-220启拆形式.LM2576里面包罗52kHz振荡器、1.23V基准稳压电路、热闭断电路、电流节造电路、搁大器、比较器及里面稳压电路等.为了爆收分歧的输出电压，常常将比较器的背端接基准电压(1.23V)，正端接分压电阻搜集，那样可根据输出电压的分歧选定分歧的阻值，其中R1=1kΩ(可调-ADJ时启路)， R2分别为1.7 kΩ(3.3V)、3.1 kΩ(5V)、8.84 kΩ(12V)、11.3 kΩ(15V)战0(-ADJ)，上述电阻依据型号分歧已正在芯片里面干了透彻安排，果而无需使用者思量.将输出电压分压电阻搜集的输出共里面基准稳压值 1.23V举止比较，若电压有偏偏好，则可用搁大器统造里面振荡器的输出占空比，进而使输出电压脆持宁静.由图1及LM2576系列启闭稳压集成电路的个性不妨瞅出，以LM2576为核心的启闭稳压电源实足不妨与代三端稳压器件形成的MCU稳压电源.2 LM2576应用举例2.1 基础应用安排由LM2576形成的基础稳压电路仅需四个中围器件，其电路如图1所示.电感L1的采用要根据LM2576的输出电压、最大输进电压、最大背载电流等参数采用，最先，依据如下公式估计出电压·微秒常数(E·T)：E·T=(Vin - V out)×V out/ Vin×1000/f?? (1)上式中，Vin是LM2576的最大输进电压、V out是LM2576的输出电压、f是LM2576的处事振荡频次值(52kHz).E·T决定之后，便可参照参照文件所提供的相映的电压·微秒常数战背载电流直线去查找所需的电感值了.(下图为：图三)该电路中的输进电容Cin普遍应大于或者等于100μF，拆置时央供尽管靠拢LM2576的输进引足，其耐压值应与最大输进电压值相匹配.而输出电容Cout的值应依据下式举止估计(单位μF)：C≥13300 Vin/ V out×L (2)上式中，Vin是LM2576的最大输进电压、V out是LM2576的输出电压、L是经估计并查表选出的电感L1的值，其单位是μH.电容C铁耐压值应大于额定输出电压的1.5～2倍.对付于5V电压输出而止，推荐使用耐压值为16V的电容器.二极管D1的额定电流值应大于最大背载电流的1.2倍，思量到背载短路的情况，二极管的额定电流值应大于LM2576的最大电流节造.二极管的反背电压应大于最大输进电压的1.25倍.参照文件中推荐使用1N582x系列的肖特基二极管.Vin的采用应试虑接流电压最矮跌降值(Vac-min)所对付应的LM2576输进电压值及LM2576的最小输进允许电压值Vmin(以5V电压输出为例，该值为8V)，果此，Vin可依据下式估计：Vin≥(220Vmin/Vac-min)如果接流电压最矮允许跌降30%(Vac-min=154V)、LM2576的电压输出为5V(Vmin=8V)，则当Vac=220V时，LM2576的输进直流电压应大于11.5V，常常可选为12V. 2.2 处事模式可控应用安排LM2576的5足输进电仄可用于统造LM2576的处事状态.5足输进电仄与TTL电仄兼容.当输进为矮电通常，LM2576仄常处事;当输进为下电通常，LM2576停止输出并加进矮功耗状态.图3是LM2576的处事模式可控电路本理图.图3中，下推电阻可包管MCU-CON统造端为矮时LM2576的仄常处事.Shutdown Input的统造端旗号去自MCU，该端为矮电通常，LM2576停止输出，系统加进矮功耗状态.当为该端为下电通常，三极管导通会使LM2576沉新处事.安排时包管当MCU-CON统造端为下电仄且三极管导通时，电阻R没有至于果过流而益坏MCU的输出统造端.。

开关型稳压芯片LM2576中文资料

开关型稳压芯片LM2576中文材料之杨若古兰创作LM2576系列开关稳压集成电路是线性三端稳压器件(如78xx 系列端稳压集成电路)的替代品，它具有可靠的工作功能、较高的工作效力和较强的输出电流驱动能力，从而为MCU 的波动、可靠工作提供了强无力的包管.LM2576简介LM2576系列是美国国家半导体公司生产的3A电流输出降压开关型集成稳压电路，它内含固定频率振荡器(52kHz)和基准稳压器(1.23V)，并具有完美的呵护电路，包含电流限制及热关断电路等，利用该器件只需极少的核心器件即可构成高效稳压电路.LM2576系列包含LM2576(最高输入电压40V)及LM2576HV(最高输入电压60V)二个系列.各系列产品均提供有3.3V(-3.3)、5V(-5.0)、12V(-12)、15V(-15)及可调(-ADJ)等多个电压档次产品.此外，该芯片还提供了工作形态的内部控制引脚.LM2576系列开关稳压集成电路的次要特性如下[2]：●最大输出电流：3A;●最高输入电压：LM2576为40V，LM2576HV为60V;●输出电压：3.3V、5V、12V、15V和ADJ(可调)等可选;●振东频率：52kHz;●转换效力：75%～88%(分歧电压输出时的效力分歧);●控制方式：PWM;●工作温度范围：-40℃～+125℃●工作模式：低功耗/正常两种模式可内部控制;●工作模式控制：TTL电平兼容;●所需内部元件：仅四个(不成调)或六个(可调);●器件呵护：热关断及电流限制;●封装方式：TO-220或TO-263.LM2576的内部框图如图1所示，该框图的引脚定义对应于五脚TO-220封装方式.LM2576内部包含52kHz振荡器、1.23V基准稳压电路、热关断电路、电流限制电路、放大器、比较器及内部稳压电路等.为了发生分歧的输出电压，通常将比较器的负端接基准电压(1.23V)，正端接分压电阻收集，如许可根据输出电压的分歧选定分歧的阻值，其中R1=1kΩ(可调-ADJ时开路)，R2分别为1.7 kΩ(3.3V)、3.1 kΩ(5V)、8.84 kΩ(12V)、11.3 kΩ(15V)和0(-ADJ)，上述电阻根据型号分歧已在芯片内部做了精确调整，因此无需使用者考虑.将输出电压分压电阻收集的输出同内部基准稳压值1.23V进行比较，若电压有偏差，则可用放大器控制内部振荡器的输出占空比，从而使输出电压坚持波动.由图1及LM2576系列开关稳压集成电路的特性可以看出，以LM2576为核心的开关稳压电源完整可以取代三端稳压器件构成的MCU稳压电源.2 LM2576利用举例2.1 基本利用设计由LM2576构成的基本稳压电路仅需四个核心器件，其电路如图1所示.电感L1的选摘要根据LM2576的输出电压、最大输入电压、最大负载电流等参数选择，首先，根据如下公式计算出电压·微秒常数(E·T)：E·T=(Vin - Vout)×Vout/ Vin×1000/f?? (1)上式中，Vin是LM2576的最大输入电压、Vout是LM2576的输出电压、f是LM2576的工作振荡频率值(52kHz).E·T确定以后，就可参照参考文献所提供的响应的电压·微秒常数和负载电流曲线来查找所需的电感值了.(下图为：图三)该电路中的输入电容Cin普通应大于或等于100μF，安装时请求尽量靠近LM2576的输入引脚，其耐压值应与最大输入电压值相匹配.而输出电容Cout的值应根据下式进行计算(单位μF)：C≥13300 Vin/ Vout×L (2)上式中，Vin是LM2576的最大输入电压、Vout是LM2576的输出电压、L是经计算并查表选出的电感L1的值，其单位是μH.电容C铁耐压值应大于额定输出电压的1.5～2倍.对于5V电压输出而言，推荐使用耐压值为16V的电容器.二极管D1的额定电流值应大于最大负载电流的1.2倍，考虑到负载短路的情况，二极管的额定电流值应大于LM2576的最大电流限制.二极管的反向电压应大于最大输入电压的1.25倍.参考文献中推荐使用1N582x系列的肖特基二极管.Vin的选择应考虑交流电压最低跌落值(Vac-min)所对应的LM2576输入电压值及LM2576的最小输入答应电压值Vmin(以5V电压输出为例，该值为8V)，是以，Vin可根据下式计算：Vin≥(220Vmin/Vac-min)如果交流电压最低答应跌落30%(Vac-min=154V)、LM2576的电压输出为5V(Vmin=8V)，则当Vac=220V时，LM2576的输入直流电压应大于11.5V，通常可选为12V. 2.2 工作模式可控利用设计LM2576的5脚输入电平可用于控制LM2576的工作形态.5脚输入电平与TTL电平兼容.当输入为低电平时，LM2576正常工作;当输入为高电平时，LM2576停止输出并进入低功耗形态.图3是LM2576的工作模式可控电路道理图.图3中，下拉电阻可包管MCU-CON控制端为低时LM2576的正常工作.Shutdown Input的控制端旌旗灯号来自MCU，该端为低电平时，LM2576停止输出，零碎进入低功耗形态.当为该端为高电平时，三极管导通会使LM2576从头工作.设计时包管当MCU-CON控制端为高电平且三极管导通时，电阻R不至于因过流而损坏MCU的输出控制端.。

实例一款升压芯片的数据手册解读

实例一款升压芯片的数据手册解读
升压芯片的种类繁多，不同芯片的数据手册内容也不禁相同，如何正确的理解并读懂这些数据手册关系着是否能将电源做出最终正确的设计。

在本文中，小编将以一款芯片的数据手册内容为例，对其内容进行分析，并对该款芯片的升压原理进行解读。

LM2577-ADJ开关电源芯片被整体整合在集成电路中，为反激变换开关调节器和前锋转换开关调节器提供电源并且控制这两个调节器。

这个芯片可用于三中不同的输出电压，分别是12V、15V和可调电压。

LM2577-ADJ需要最少的外部器件，那些调节器有非常高的效率而且易于使用，被列在数据表上的是基础电感和反激变换开关调节器一起的被设计用来和那些转换调节器相互工作。

在芯片中有一个3.0ANPN开关及其有关保护电路，组成的电流和热限制，锁定和馈线线路(设备)。

其他特点包括52千赫的振动，不需要外部的频振元件，一个in-rush电流减少时的软启动方式，启动电流模式控制，有效阻止输入电压和输出负载电涌。

特性：
1、需要很少的外部组件。

2、NPN输出转换3.0A，能避开65V电压。

3、输入电压范围宽度：3.5V-40V。

4、为改善瞬态电流型操作而响应、线、电流限制条例。

5、52千赫内部振荡器。

6、Soft-start功能，减少in-rush起动电流。

7、输出电流限制开关保护、低、停工、热关机。

典型应用。

lm2577升压工作原理

lm2577升压工作原理LM2577是一种升压转换器，也被称为升压稳压器。

它的工作原理是将输入的直流电压转换为输出的高电压直流电压。

LM2577采用了开关电源技术，通过控制开关管的导通和截止来实现电压的转换。

LM2577的工作原理可以分为三个步骤：输入电压的整流、开关管的控制和输出电压的滤波。

输入电压经过整流电路转换为直流电压。

整流电路通常由二极管桥整流电路组成，用于将交流电转换为直流电。

整流后的直流电压输入到升压稳压器的控制电路中。

控制电路通过对开关管的控制，实现了输入电压的升压转换。

控制电路通常由比较器、振荡器和驱动电路组成。

比较器用于比较反馈电压和参考电压，根据比较结果控制开关管的导通和截止。

振荡器产生一个固定频率的方波信号，用于控制开关管的开关动作。

驱动电路将振荡器产生的方波信号转换为开关管的控制信号，控制开关管的导通和截止。

当开关管导通时，输入电压通过升压电感和开关管传递到输出端，从而实现了电压的升压。

当开关管截止时，电感中储存的能量通过二极管传递到输出端，保持输出电压的稳定性。

输出电压经过滤波电路进行滤波处理，去除掉交流成分，得到稳定的直流电压。

滤波电路通常由电容器和电感器组成。

电容器可以储存电荷，平滑输出电压，并且能够快速响应负载变化。

电感器则用于过滤高频噪声，保证输出电压的稳定性。

LM2577升压工作原理的关键在于开关管的控制。

通过对开关管的合理控制，可以实现输入电压的升压转换，并保持输出电压的稳定性。

LM2577具有高效率、高可靠性和低功耗的特点，广泛应用于电源供应、通信设备和工控设备等领域。

LM2577升压工作原理是通过开关电源技术实现的。

它通过控制开关管的导通和截止，将输入的直流电压转换为输出的高电压直流电压。

LM2577的工作原理经过整流、开关管的控制和输出电压的滤波三个步骤，最终实现了电压的升压转换和稳定输出。

这一工作原理使得LM2577在各种电子设备中得到了广泛的应用。

芯片lm2576-adj

引言开关电源以其体积小、重量轻、变换效率高被广泛应用于电子设备中。

其电路拓扑有多种形式,无工频变压器的开关电源最具吸引力,但这种电源只适用于输出电压固定或变化范围不大的场合,而不适和要求输出电压幅度变化很大或连续可调的场合。

利用单片式开关稳压器LM2576-ADJ 替代线性稳压器构成串联开关式稳压电源,在电路中只需增加续流二极管和储能电感等几只元器件,使电路更加简洁,除具有线性电源宽范围连续可调的优点外,同时使电源效率得到了大幅度提高,在负载较轻时,不加散热器也能正常工作,又使整机的重量和体积有所减少。

2 LM2576-ADJ 简介LM2576-ADJ 美国NS 公司生产的单片降压式开关稳压器,由振荡器、取样放大器、比较器、PWM 调制器、功率开关等部分组成。

采用TO-220 封装,仅有5只管脚,外形和塑封晶体管差不多。

其功能框图及引脚排列如图1、图2 所示。

图1 LM2576 功能框图图2 LM2576 引脚排列LM2576-ADJ 是输出电压可调型,其技术参数为:输入电压3. 5～40V ;输出电压1. 23～37V ;输出电流3A ;振荡器固定频率52kHz ;TTL 关闭能力及低功率备用状态;具有热关闭和限流保护功能。

其典型应用电路如图 3 所示(输出电压连续可调) ,当直流输出端直接接于控制端 4 脚时,可输出固定电压。

LM2576系列产品是现流行的三端线性调整器的替代品。

图3 LM2576-ADJ 典型应用电路3 LM2576-ADJ 构成单片开关电源3. 1 工作原理交流电经电源变压器隔离降压再经桥式整流滤波后,加到LM2576-ADJ 输入端1 脚。

稳压器控制端4 脚接于电位器W和电阻R 组成的分压电路上,改变W即可改变分压比,就能调节其输出电压大小。

Vo = U REF(1 +W/R) ,其中U REF为稳压器取样电路基准电压为1. 23V。

C1输入端滤波电容, C2、C3输出端滤波电容如图4 所示。

LM2577模块原理图

LM2577模块原理图
LM2577属于单片集成电路，是很常用的升降压电源IC，在升压电路中较常用，属于TI
公司生产的芯片，该芯片外围电路少，使用简单。

该芯片有三个不同的电压输出版本：
12V、15V、ADJ（可调），芯片最高耐压65V，其输入电压范围为3.5V~40V，输出电压
最高可达60V，芯片内部有额定电流为3A的NPN开关晶体管，有过流、热限制以及欠压锁定等相关保护电路，内部有52KHZ的固定频率振荡器，具有软启动功能，冲击电流小。

LM2577芯片
该芯片有5个引脚，各引脚的功能分别是：1脚-COMP，接补偿电容和补偿电阻；2脚-feedback(反馈脚），反馈取样电压输入引脚，基准电压为1.23V；3脚-GND，接地；4脚
-switch，转换引脚；5脚-VIN，电源输入引脚。

下图为输入5V，输出12V的官方典型原理图，输出电压公式为VOUT=1.23V×
（1+R1/R2）。

验证：下图输出Vout=1.23V×（1+R1/R2）=1.23V×（1+17.4K/2K）≈11.93V。

LM2577-ADJ原理图
实例说明：
下面举例介绍LM2577模块原理，可实现电压输入范围3.5V~40V，电压输出范围
1.23V~60V，通过调节电位器R1可改变输出电压。

LM2577模块原理图
LM2577模块
该模块非常好用，效率高，不但可以升压还可以降压，不过很少在降压当中使用，最常用的是升压，最大输出电流为3A。

LM2577 中文资料

LM1577/LM2577的SIMPLE SWITCHER®升压型稳压器检查样品：LM1577，LM2577特点23•需要很少的外部元件•NPN输出开关3.0A，可以滚开65V•宽输入电压范围：3.5V至40V•电流模式工作，从而提高瞬态响应，线路调整，以及电流限制•52 kHz内部振荡器•软启动功能降低浪涌电流在启动过程中•输出通过开关电流限制保护，欠压锁定和热关闭说明该LM1577/LM2577是单片集成电路，提供所有的权力和控制步升（升压），反激和正向功能转换器的开关稳压器。

该装置是有三种不同的输出电压版本：12V，15V，和可调。

需要的外部的最小数目组件，这些监管机构的成本效益，并使用简单。

列在本数据表是一个家庭的标准电感和反激式变压器设计与这些开关稳压器配合工作。

包括在芯片上是一个3.0A NPN开关及其相关的保护电路，包括电流和热限制和欠压锁定的。

其他功能包括一个52 kHz的固定频率振荡器，无需外部元件，软启动模式，以降低浪涌电流在启动过程中，并电流模式控制输入的改进的排斥反应电压和输出负载瞬变。

典型应用•简单的升压型稳压器•反激和正向调节器•多路输出调节器连接图图15引脚（直引线）TO-220（T）图2。

5引脚（弯曲，交错引线）TO-220（T）图316引脚PDIP（N）图424引脚SOIC封装（M）图5引脚DDPAK/TO-263（S）SFM包装6，5引脚DDPAK/TO-263（S）SFM包装图74引脚TO-220（K）- 底视图典型用途注：所示引脚号为TO-220（T）包装。

这些器件具有有限的内置ESD保护。

导线应短接在一起或设备放置在导电泡棉储存或搬运过程中防止对静电损坏MOS大门。

绝对最大额定值（1）（2）（1）绝对最大额定值表明，超过这个可能会损坏设备的限制。

工作额定值表明条件设备旨在是功能性的，但设备参数规格可能不这些条件下得到保证。

为确保规范和测试条件，请参阅电气特性。

LM2576详细介绍

LM2576详细介绍LM2576是一款专为电源应用而设计的高效率降压稳压芯片。

它采用了功率MOSFET开关和专业设计的控制电路，能够以固定频率的方式实现恒压或恒流输出。

LM2576通过非常简单的外围器件就可以完成稳压电源设计，无需繁琐的调整和复杂的电路设计。

1.高效率：LM2576采用了开关式降压稳压的原理，相比传统的线性稳压芯片，具有更高的转换效率。

在负载较低的情况下，也能保持高效率。

2.宽输入电压范围：LM2576的输入电压范围从4V至40V，可以适应不同的电源输入条件。

3.固定输出电压：LM2576有多种型号可供选择，每种型号都有固定的输出电压。

用户可以根据需求选择不同的型号，无需调节电路即可得到所需的输出电压。

4.输出电流高：LM2576能够提供高达3A的输出电流，适用于大多数低压电源应用。

5.低输出噪声：LM2576采用了片内反馈调节电路，能够有效地抑制输出噪声。

此外，它还具有过温保护和短路保护功能，能够保证电路的可靠性和安全性。

6.简单的外围器件：LM2576的外围器件非常简单，只需一颗电容和一个电感即可实现稳压功能。

这样就减少了外围元件的数量和尺寸，可以大大减小整个电源的体积。

7.应用广泛：由于LM2576具有高效率、稳定可靠的特点，被广泛应用于工业控制、通信设备、汽车电子、电子游戏机等领域。

总结起来，LM2576是一款高效、稳定、可靠的降压稳压芯片，具有固定输出电压、宽输入电压范围和高输出电流等优点。

它适用于各种低压电源应用，可以简化电路设计，降低系统成本，提高电源的效率和可靠性。

开关型稳压芯片LM2576中文资料之欧阳法创编

开关型稳压芯片LM2576中文资料LM2576系列开关稳压集成电路是线性三端稳压器件(如78xx系列端稳压集成电路)的替代品，它具有可靠的工作性能、较高的工作效率和较强的输出电流驱动能力，从而为MCU的稳定、可靠工作提供了强有力的保证。

LM2576简介LM2576系列是美国国家半导体公司生产的3A电流输出降压开关型集成稳压电路，它内含固定频率振荡器(52kHz)和基准稳压器(1.23V)，并具有完善的保护电路，包括电流限制及热关断电路等，利用该器件只需极少的外围器件便可构成高效稳压电路。

LM2576系列包括LM2576(最高输入电压40V)及LM2576HV(最高输入电压60V)二个系列。

各系列产品均提供有3.3V(-3.3)、5V(-5.0)、12V(-12)、15V(-15)及可调(-ADJ)等多个电压档次产品。

此外，该芯片还提供了工作状态的外部控制引脚。

LM2576系列开关稳压集成电路的主要特性如下[2]：●最大输出电流：3A;●最高输入电压：LM2576为40V，LM2576HV为60V;●输出电压：3.3V、5V、12V、15V和ADJ(可调)等可选;●振东频率：52kHz;●转换效率：75%～88%(不同电压输出时的效率不同);●控制方式：PWM;●工作温度范围：-40℃～+125℃●工作模式：低功耗/正常两种模式可外部控制;●工作模式控制：TTL电平兼容;●所需外部元件：仅四个(不可调)或六个(可调);●器件保护：热关断及电流限制;●封装形式：TO-220或TO-263。

LM2576的内部框图如图1所示，该框图的引脚定义对应于五脚TO-220封装形式。

LM2576内部包含52kHz振荡器、1.23V基准稳压电路、热关断电路、电流限制电路、放大器、比较器及内部稳压电路等。

为了产生不同的输出电压，通常将比较器的负端接基准电压(1.23V)，正端接分压电阻网络，这样可根据输出电压的不同选定不同的阻值，其中R1=1kΩ(可调-ADJ时开路)，R2分别为 1.7 kΩ(3.3V)、3.1 kΩ(5V)、8.84 kΩ(12V)、11.3 kΩ(15V)和0(-ADJ)，上述电阻依据型号不同已在芯片内部做了精确调整，因而无需使用者考虑。

常用功放升压ic

常用功放升压ic功放升压 IC（Integrated Circuit）是一种集成了升压功能的电路芯片，通常用于提升电源电压以满足某些电子设备的要求。

以下是一些常用的功放升压 IC：LM2577/LM2577T系列：* 制造商： National Semiconductor（现在是德州仪器 - Texas Instruments）* 特点：调节式升压稳压器，可提供可调输出电压。

MT3608：* 制造商： Monolithic Power Systems* 特点： 2A DC-DC 升压模块，适用于小型电源升压应用。

XL6009：* 制造商： XLSemi（杰力半导体）* 特点：可调升压 DC-DC 转换器，适用于多种应用，例如电子设备和 DIY 电源。

MAX1771：* 制造商： Maxim Integrated* 特点：高效、低成本、可调的升压 DC-DC 转换器，适用于电池供电设备。

TPS61200：* 制造商： Texas Instruments* 特点：低功耗、高效率的 1.8V 至 5.5V 输入电压范围的升压转换器。

LT1370：* 制造商： Linear Technology（现在是ADI - AnalogDevices）* 特点：高效率的升压 DC-DC 转换器，适用于工业和通信应用。

ADM7150：* 制造商： Analog Devices* 特点：高性能低压差稳压器（LDO）和升压 DC-DC 转换器的组合。

UC3843：* 制造商： ON Semiconductor* 特点： PWM 控制的升压 DC-DC 转换器控制器。

这些 IC 提供了不同的电压升压范围、电流容量和特性，以满足各种应用的需求。

选择合适的功放升压 IC 取决于具体的设计要求和应用场景。

正压转负压电路LM2576

3A正压转负压电路.ddb
主要是为把+5V电压转换出一个-5V电压用
采用 LM2576-ADJ 3A输出可调电源芯片制作，开关频率50KHZ
该电路的典型应用是降压，因为是斩波式降压，所以效率比较高能达到80%
输入电压5V~40V,输出1.2V~37V
代替DCDC模块和7805等效果都不错
3A正压转负压电路
输入电压4.5V~30V 输出-1.25~-25V 最大电流可接近3A，静态电流10mA~20mA
可以用于需要负电源的场合
成本较低 LM2576-ADJ为1.5元/片
LM2575为最大电流1A的芯片，可以直接替换
LM2595,LM2596开关频率150KHZ，需要的电感能小一些，但开关损耗可能就大一些，引脚都一样
如果购买，可能会遇到假货，LM2575直插假货和LM2596贴片假货都遇到过
LM2576质量还不错，直插贴片都正常
这张图比较小，大图看rar的protel文件，原理带着解释。

lm2577升压工作原理

lm2577升压工作原理LM2577是一种常用的升压型DC-DC转换器芯片，其工作原理基于开关电源技术。

本文将详细介绍LM2577升压工作原理。

一、LM2577的基本结构和工作原理LM2577芯片由输入电压检测电路、PWM控制电路、开关管驱动电路、功率开关管、输出电压反馈电路和输出电流保护电路等组成。

1. 输入电压检测电路：LM2577的输入电压检测电路主要用于检测输入电压是否达到芯片工作的最低电压要求。

如果输入电压低于最低电压要求，芯片将不会启动。

2. PWM控制电路：PWM控制电路是LM2577的核心部分，用于产生高频脉冲信号。

这个信号的占空比决定了开关管的导通时间和关断时间，从而影响转换效率和输出电压。

3. 开关管驱动电路：开关管驱动电路用于驱动功率开关管。

当PWM控制电路产生高电平信号时，开关管导通，当PWM控制电路产生低电平信号时，开关管关断。

4. 功率开关管：功率开关管是LM2577的核心元件，它可以实现输入电压的升压。

当开关管导通时，输入电压通过电感储能，当开关管关断时，储能电感将其储存的能量传递给输出回路，实现输出电压的升压。

5. 输出电压反馈电路：输出电压反馈电路用于监测输出电压，并将反馈信号送回PWM控制电路，通过调节占空比来稳定输出电压。

6. 输出电流保护电路：输出电流保护电路用于监测输出电流，当输出电流超过一定阈值时，保护电路将关闭开关管，以保护电路和负载。

二、LM2577的升压工作原理LM2577的升压工作原理可以分为四个阶段：导通、储能、关断和输出。

1. 导通阶段：在导通阶段，PWM控制电路产生高电平信号，驱动开关管导通。

此时，输入电压通过电感储能，并将能量传递给输出回路，输出电压开始升高。

2. 储能阶段：在储能阶段，开关管关断，电感储能器将能量储存起来。

此时，输出电压继续上升。

3. 关断阶段：在关断阶段，PWM控制电路产生低电平信号，驱动开关管关断。

此时，储能电感将其储存的能量传递给输出回路，输出电压继续上升。

电源芯片资料LM2577

LM2578AM资料

lm2577隔离式dcdc开关电源的设计

LM2577-12中文资料

LM2577中文资料

模拟电子技术基础-lm2576电源转换电路

LM2576芯片

开关型稳压芯片LM2576中文资料

开关型稳压芯片LM2576中文资料

实例 一款升压芯片的数据手册解读

lm2577升压工作原理

芯片lm2576-adj

LM2577模块原理图

LM2577 中文资料

LM2576详细介绍

开关型稳压芯片LM2576中文资料之欧阳法创编

常用功放升压ic

正压转负压电路LM2576

lm2577升压工作原理

实例一款升压芯片的数据手册解读