LM50BIM3中文资料

-Leading Performance specifications ● Fixed Voltage and Adjustable VersionsAPPLICATIONS● Battery Powered Equipment● High-Efficiency " Green" Computer System ● Automotive Electronics● High-Efficiency Linear Power Supplies ● High-Efficiency Post-Regulator For Switching SupplyORDERING INFORMATIONPinoutLM29150: Three Therminal DevicesLM29151: Five Therminal Fixed Voltage Devices LM29152: Adjustable with ON/OFF controlLM29153: Adjustable with Flag * LM29151 - X.X (X.X = Output Voltage = 1.5V, 2.5V, 3.0V, 3.3V, 5.0V, 12V `DESCRIPTIONThe LM29150 are high current, high accuracy, low-dropout voltage regulators. Using process with a PNP pass element, these regulators feature 350mV (full load) dropout voltages and very low ground current.These devices also find applications in lower current, low dropout-critical systems, where their tiny dropout voltage and graound current values are important attributes.The LM29150 are fully protected against over current faults, reversed input polarity, reversed lead insertion, over temperature operation, and positive and negative transient voltage spikes. Five pin fixed voltage versions feature logic level ON/OFF control and an error flag which signals whenever the output falls out of regulation.On the LM29150 and LM29152, the ENABLE pin may be tied to Vin if it is not required for ON/OFF control.The LM29150 are available in 3- and 5- pinTO-220 and surface mount TO-263 packages.LM29150 - X.X LM29150RS - X.X LM29152/3LM29152RS/3RS - X.X LM29152/3DeviceLM29152R/3R LM29150R - X.X LM29151 - X.X LM29151RS - X.X LM29151R - X.X TO-263 5LMarkingLM29150 - X.X LM29151 - X.X TO-252 5LTO-263 5LTO-220 5LPin 1= Input, 2= Ground, 3= Output Package TO-220 3L TO-252 5L Pin 1= Flag, 2= Input, 3=Ground, 4=Output, 5= Adjust Pin 1= Enable, 2= Input, 3=Ground, 4=Output, 5= Adjust Pin 1= Enable, 2= Input, 3=Ground, 4=Output, 5= Flag TO-252 3L TO-263 3L TO-220 5L TO-263 3/5LTO-252 3/5LBlock Diagram and typical Application Circuit94[ Block Diagram ]* Feed Back network in fixed versions only **Adjustable version onlyVout=1.240V x [1+(R1/R2)]Figure2. Adjstable output voltageconfiguration. For best results, the totalseries resistance should be small enough to pass the minimum regulator load currentLMABSOULTE MAXIMUM RATINGSLead Temperature(Soldering, 5 Seconds)Storage Temperature Range Input Supply Voltage(Note 1)OPERATING RATINGSOperating Junction Temperature Maximum Operating Input VoltageELECTRICAL CHARACTERISTICS IOUT =100㎃, T A =25℃, unless otherwise specifiedAll measurements at Tj=25℃ unless otherwise noted. Bold Values are guaranteed across the operating temperature range.Adjustable versions are programmed to 5.0V-40℃ to + 125℃'26VCHARACTERISTICInternally Limit -20℃ to + 60℃'Internally LimitCHARACTERISTIC260℃-65℃ to + 150℃LM29150LM29152[ Note. ]1. Maximum positive supply voltage of 60V must be of limited duration (<100msec) and duty cycle(≤1%). The maximum continuous supply voltage is 26V2. Full load current(IFL ) is defined as 1.5A3. Dropout voltage is defined as the input-to-output differential when the output voltage drops to 99% of its nominal value with Vout to Vin4. Vin = Vout(nominal) +1V. For example, use Vin =4.3V for a 3.3V regulator or use 6V for a 5V regulator. Employ pulse-testing procedures to minimize temperature rise.5. Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin current.6. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.7. Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse at Vin= 20V (a 4W pulse) for T= 10ms8. Vref ≤ Vout ≤ (Vin -1V), 2.3V ≤ Vin ≤ 26V, 10mA＜IL IFL, TJ＜ TJ Max9. Comparator thresholds are expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage measured at. 6V input. To express these thresholds in terms of output voltage change,multiply by the error amplifier gain = Vout/Vref = (R1 +R2)/R2. For example, at a programmed output voltage of 5V, the Error output is guaranteed to go low when the output drops by 95mV x 5V/ 1.240V - 384mV.Thresholds remain constant as a percent of Vout as Vout is varied, with the dropout warining occurring at typically 5% below nominal, 7.7% guaranteed.10. Ven ≤ 0.8V and Vin≤26V, Vout=011. When used in dual supply system where the regulator load is returned to a negative supply, the output Voltage must be diode clamped to ground.TYPICAL PERFORMANCE CHARACTERISTICSFigure 1. LM29150 Dropout Voltage vs,Output Current Figure 2. LM29150 Dropout Voltage vs,TemperatureFigure 3. LM29150- 5.0 DropoutCharacteristicsFigure 4. LM29150 Ground Current vs,Supply Voltage Figure 5. LM29150 Ground Current vs,TemperatureFigure 6. LM29150 Ground Current vs,TemperatureFigure 7. LM29150-3.3 Output Voltage vs.Temperature Figure 8. LM29150-3.3 Short CircuitCurrent vs. TemperatureFigure 9. LM29150 Ground Current vs.Input VoltageApplications InformationThe LM29150 are high performance low-dropout voltage regulators suitable for all moderate to high -current voltage regulator applications. Their 350mV dropout voltage at full load make them especially valuable in battery powered systems and as high efficiency noise filters in"post-regulator" applications. Unlike older NPN-pass transistor designs, dropout performance of the PNP output of these devices is limited merely by the low Vce saturation voltage.The LM29150 family of regulators is fully protected from damage due to fault conditions. Current Limiting is provided. This limiting is linear; output current under overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds the 125℃ maximum safe operating temperature. Transient protection allows device survival even when the input voltage spikes between -20V and +60V. When the input voltage exceeds about 35V to 40V. The over voltage sensor temporarily disables the regulator.Figure 3. Linear regulators require only two capacitorsfor operation.Thermal DesignLinear regulators are simple to use. The most complicated design parameters to consider are thermal characteristics. Thermal design requires the following application-specific parameters: *Maximum ambient temperature, T A*Output Current, I OUT*Output Voltage, V OUT*Input Voltage, V INFirst, we calculate the power dissipation of the regulator from these numbers and the device parameters from this datasheet.P D=I OUT(1.01V IN-V OUT)Where the ground current is approximated by 1% of I OUT. Then the heat sink thermalresistance is determined with this formula:Where TJ MAX≤ 125℃ and ΘCS is between 0 and 2℃/W.Capaitor RequirementsFor stability and minimum output noise,a capacitor on the regulator output is necessary. Thevalue of this capacitor is dependent upon the output current; lower currents allow smaller capcitors. LM29150 regulators are stable with the 10uF minimum capacitor values at full load. Where the regulator is powered from a source with a high AC impedance, a 0.1uF capacitor connected between input and GND is recommended. This capacitor should have good characteristics to above 250kHz.Minimum Load CurrentThe LM29150 regulators are specified between finite loads. If the output is too small, leakage currents is too small, leakage currents dominate and the output voltage rises. The 5mA minimum load current swamps any expected leakage current across the operating temperature range.Adjustable Regulator DesignFigure 4.Adjustable Regulator with ResistorsThe adjustable regulator versions, LM29152 and LM29153, allow programming the output voltage anywhere between 1.25V and the 26V maximum operating rating of the family.Two resistors are used. Resistors can be quite large, up to 1MΩ, because of the very high input impedance and low bias current of the sense comparator: The resistor values are calculated by:Where is VO the desired output voltage. Figure 4 shows component definition. Applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation.Error FlagLM29151 and LM29153 versions feature and Error Flag, which looks at the output voltage and signals and error condition when this voltage and signals an error condition when this voltage drops 5% below its expected value. The error flag is an open-collector output that pulls low under fault conditions. It may sink 10mA. Low output voltage signifies a number of possible problems, including an over-current fault (the device is in current limit) and low input voltage.The flag output is inoperative during over temperature shutdwon conditions.Enable inputLM29151 and LM29152 versions feature and enable (EN) input that allows ON/OFF control of the device. Special design allows "zero" current drain when the device is disabled-only microamperes of leakage current flows. The EN input has TTL/CMOS compatible thresholds for simple interfacing with logic, or may be directly tied to ≤ 30V. Enabling the regulator requires approximately 20uA of current.VOUT=1.240V x [ 1+(R1/R2)]。

LM50SOT-23Single-Supply Centigrade Temperature SensorGeneral DescriptionThe LM50is a precision integrated-circuit temperature sen-sor that can sense a −40˚C to +125˚C temperature range us-ing a single positive supply.The LM50’s output voltage is lin-early proportional to Celsius (Centigrade)temperature (+10mV/˚C)and has a DC offset of +500mV.The offset al-lows reading negative temperatures without the need for a negative supply.The ideal output voltage of the LM50ranges from +100mV to +1.75V for a −40˚C to +125˚C temperature range.The LM50does not require any external calibration or trimming to provide accuracies of ±3˚C at room temperature and ±4˚C over the full −40˚C to +125˚C temperature range.Trimming and calibration of the LM50at the wafer level as-sure low cost and high accuracy.The LM50’s linear output,+500mV offset,and factory calibration simplify circuitry re-quired in a single supply environment where reading nega-tive temperatures is required.Because the LM50’s quiescent current is less than 130µA,self-heating is limited to a very low 0.2˚C in still air.Applicationsn Computers n Disk Drivesn Battery Management n Automotive n FAX Machines n Printersn Portable Medical Instruments n HVACnPower Supply ModulesFeaturesn Calibrated directly in degree Celsius (Centigrade)n Linear +10.0mV/˚C scale factor n ±2˚C accuracy guaranteed at +25˚C n Specified for full −40˚to +125˚C range n Suitable for remote applicationsn Low cost due to wafer-level trimming n Operates from 4.5V to 10V n Less than 130µA current drainn Low self-heating,less than 0.2˚C in still air nNonlinearity less than 0.8˚C over tempConnection DiagramOrder SOT-23Supplied As Number Device MarkingLM50BIM3T5B 1000Units on Tape and ReelLM50CIM3T5C 1000Units on Tape and ReelLM50BIM3X T5B 3000Units on Tape and ReelLM50CIM3XT5C3000Units on Tape and ReelTypical ApplicationSOT-23DS012030-1Top ViewSee NS Package Number MA03BDS012030-3FIGURE 1.Full-Range Centigrade Temperature Sensor (−40˚C to +125˚C)July 1999LM50SOT-23Single-Supply Centigrade Temperature Sensor©1999National Semiconductor Corporation Absolute Maximum Ratings(Note1)Supply Voltage+12V to−0.2V Output Voltage(+V S+0.6V)to−1.0V Output Current10mA Storage Temperature−65˚C to+150˚C Lead Temperature:SOT Package(Note2):Vapor Phase(60seconds)215˚C Infrared(15seconds)220˚C T JMAX,MaximumJunction Temperature150˚C ESD Susceptibility(Note3):Human Body ModelMachine Model2000V250V Operating Ratings(Note1)Specified Temperature Range:T MIN to T MAX LM50C−40˚C to+125˚C LM50B−25˚C to+100˚C Operating Temperature Range−40˚C to+150˚C θJA(Note4)450˚C/W Supply Voltage Range(+V S)+4.5V to+10VElectrical CharacteristicsUnless otherwise noted,these specifications apply for V S=+5V DC and I LOAD=+0.5µA,in the circuit of Figure1.Boldface limits apply for the specified T A=T J=T MIN to T MAX;all other limits T A=T J=+25˚C,unless otherwise noted.Parameter Conditions LM50B LM50C Units(Limit)Typical Limit Typical Limit(Note5)(Note5)Accuracy T A=+25˚C±2.0±3.0˚C(max) (Note6)T A=T MAX±3.0±4.0˚C(max)T A=T MIN+3.0,−3.5±4.0˚C(max) Nonlinearity(Note7)±0.8±0.8˚C(max) Sensor Gain+9.7+9.7mV/˚C(min) (Average Slope)+10.3+10.3mV/˚C(max) Output Resistance2000400020004000Ω(max) Line Regulation+4.5V≤V S≤+10V±0.8±0.8mV/V(max) (Note8)±1.2±1.2mV/V(max) Quiescent Current+4.5V≤V S≤+10V130130µA(max) (Note9)180180µA(max) Change of Quiescent+4.5V≤V S≤+10V 2.0 2.0µA(max) Current(Note9)Temperature Coefficient of+1.0+2.0µA/˚C Quiescent CurrentLong Term Stability(Note10)T J=125˚C,for±0.08±0.08˚C1000hoursNote1: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.Note2:See AN-450“Surface Mounting Methods and Their Effect on Product Reliability”or the section titled“Surface Mount”found in a current National Semicon-ductor Linear Data Book for other methods of soldering surface mount devices.Note3:Human body model,100pF discharged through a1.5kΩresistor.Machine model,200pF discharged directly into each pin.Note4:Thermal resistance of the SOT-23package is specified without a heat sink,junction to ambient.Note5:Limits are guaranteed to National’s AOQL(Average Outgoing Quality Level).Note6:Accuracy is defined as the error between the output voltage and10mv/˚C times the device’s case temperature plus500mV,at specified conditions of volt-age,current,and temperature(expressed in˚C).Note7:Nonlinearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line,over the device’s rated temperature range.Note8:Regulation is measured at constant junction temperature,using pulse testing with a low duty cycle.Changes in output due to heating effects can be com-puted by multiplying the internal dissipation by the thermal resistance.Note9:Quiescent current is defined in the circuit of Figure1.Note10:For best long-term stability,any precision circuit will give best results if the unit is aged at a warm temperature,and/or temperature cycled for at least46 hours before long-term life test begins.This is especially true when a small(Surface-Mount)part is wave-soldered;allow time for stress relaxation to occur.The ma-jority of the drift will occur in the first1000hours at elevated temperatures.The drift after1000hours will not continue at the first1000hour rate.2Typical Performance Characteristics To generate these curves the LM50was mounted to a printed circuit board as shown in Figure2.Thermal ResistanceJunction to AirDS012030-21Thermal Time ConstantDS012030-22Thermal Response in Still Airwith Heat Sink(Figure2)DS012030-23Thermal Responsein Stirred Oil Bathwith Heat SinkDS012030-24Start-Up Voltagevs TemperatureDS012030-25Thermal Response in StillAir without a Heat SinkDS012030-26Quiescent Current vs Temperature(Figure1)DS012030-27Accuracy vs TemperatureDS012030-28Noise VoltageDS012030-29 3Typical Performance CharacteristicsTo generate these curves the LM50was mounted to a printedcircuit board as shown in Figure 2.(Continued)1.0MountingThe LM50can be applied easily in the same way as other integrated-circuit temperature sensors.It can be glued or ce-mented to a surface and its temperature will be within about 0.2˚C of the surface temperature.This presumes that the ambient air temperature is almost the same as the surface temperature;if the air temperature were much higher or lower than the surface temperature,the ac-tual temperature of the LM50die would be at an intermediate temperature between the surface temperature and the air temperature.To ensure good thermal conductivity the backside of the LM50die is directly attached to the GND pin.The lands and traces to the LM50will,of course,be part of the printed cir-cuit board,which is the object whose temperature is being measured.These printed circuit board lands and traces will not cause the LM50s temperature to deviate from the de-sired temperature.Alternatively,the LM50can be mounted inside a sealed-end metal tube,and can then be dipped into a bath or screwed into a threaded hole in a tank.As with any IC,the LM50and accompanying wiring and circuits must be kept insulated and dry,to avoid leakage and corrosion.This is especially true if the circuit may operate at cold temperatures where conden-sation can occur.Printed-circuit coatings and varnishes suchas Humiseal and epoxy paints or dips are often used to en-sure that moisture cannot corrode the LM50or its connec-tions.Temperature Rise of LM50Due to Self-Heating (Thermal Resistance,θJA )SOT-23SOT-23no heat sink *small heat fin **Still air 450˚C/W260˚C/W Moving air180˚C/W*Part soldered to 30gauge wire.**Heat sink used is 1⁄2"square printed circuit board with 2oz.foil with part at-tached as shown in Figure 2.2.0Capacitive LoadsThe LM50handles capacitive loading very well.Without any special precautions,the LM50can drive any capacitive load.The LM50has a nominal 2k Ωoutput impedance (as can be seen in the block diagram).The temperature coefficient of the output resistors is around 1300ppm/˚C.Taking into ac-count this temperature coefficient and the initial tolerance of the resistors the output impedance of the LM50will not ex-ceed 4k Ω.In an extremely noisy environment it may be nec-essary to add some filtering to minimize noise pickup.It is recommended that 0.1µF be added from V IN to GND to by-Supply Voltage vs Supply CurrentDS012030-30Start-Up ResponseDS012030-31DS012030-19FIGURE 2.Printed Circuit Board Used for Heat Sink to Generate All Curves.1⁄2"Square Printed Circuit Boardwith 2oz.Foil or SimilarDS012030-7FIGURE 3.LM50No Decoupling Requiredfor Capacitive LoadDS012030-8FIGURE 4.LM50C with Filter for Noisy Environment 42.0Capacitive Loads(Continued)pass the power supply voltage,as shown in Figure 4.In a noisy environment it may be necessary to add a capacitor from the output to ground.A 1µF output capacitor with the 4k Ωoutput impedance will form a 40Hz lowpass filter.Sincethe thermal time constant of the LM50is much slower than the 25ms time constant formed by the RC,the overall re-sponse time of the LM50will not be significantly affected.For much larger capacitors this additional time lag will increase the overall response time of the LM50.3.0Typical ApplicationsDS012030-17*R2≈2k with a typical 1300ppm/˚C drift.FIGURE 5.Block DiagramDS012030-11FIGURE 6.Centigrade Thermostat/Fan ControllerDS012030-13FIGURE 7.Temperature To Digital Converter (Serial Output)(+125˚C Full Scale)53.0Typical Applications(Continued)DS012030-14FIGURE8.Temperature To Digital Converter(Parallel TRI-STATE®Outputs forStandard Data Bus toµP Interface)(125˚C Full Scale)DS012030-16FIGURE9.LM50With Voltage-To-Frequency Converter And Isolated Output(−40˚C to+125˚C;100Hz to1750Hz)6Physical Dimensions inches(millimeters)unless otherwise notedLIFE SUPPORT POLICYNATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.As used herein:1.Life support devices or systems are devices orsystems which,(a)are intended for surgical implantinto the body,or(b)support or sustain life,andwhose failure to perform when properly used inaccordance with instructions for use provided in thelabeling,can be reasonably expected to result in asignificant injury to the user.2.A critical component is any component of a lifesupport device or system whose failure to performcan be reasonably expected to cause the failure ofthe life support device or system,or to affect itssafety or effectiveness.National SemiconductorCorporationAmericasTel:1-800-272-9959Fax:1-800-737-7018Email:support@National SemiconductorEuropeFax:+49(0)180-5308586Email:europe.support@Deutsch Tel:+49(0)180-5308585English Tel:+49(0)180-5327832Français Tel:+49(0)180-5329358Italiano Tel:+49(0)180-5341680National SemiconductorAsia Pacific CustomerResponse GroupTel:65-2544466Fax:65-2504466Email:sea.support@National SemiconductorJapan Ltd.Tel:81-3-5639-7560Fax:81-3-5639-7507 SOT-23Molded Small Outline Transistor Package(M3)Order Number LM50BIM3,or LM50CIM3NS Package Number MA03BLM50SOT-23Single-SupplyCentigradeTemperatureSensor National does not assume any responsibility for use of any circuitry described,no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.。

January 16, 2008 LM201433A, PowerWise® Adjustable Frequency Synchronous Buck RegulatorGeneral DescriptionThe LM20143 is a full featured adjustable frequency syn-chronous buck regulator capable of delivering up to 3A of continuous output current. The current mode control loop can be compensated to be stable with virtually any type of output capacitor. For most cases, compensating the device only re-quires two external components, providing maximum flexibil-ity and ease of use. The device is optimized to work over the input voltage range of 2.95V to 5.5V making it suited for a wide variety of low voltage systems.The device features internal over voltage protection (OVP) and over current protection (OCP) circuits for increased sys-tem reliability. A precision enable pin and integrated UVLO allows the turn-on of the device to be tightly controlled and sequenced. Start-up inrush currents are limited by both an internally fixed and externally adjustable Soft-Start circuit. Fault detection and supply sequencing is possible with the integrated power good circuit.The frequency of this device can be adjusted from 500 kHz to 1.5 MHz by connecting an external resistor from the RT pin to ground.The LM20143 is designed to work well in multi-rail power supply architectures. The output voltage of the device can be configured to track a higher voltage rail using the SS/TRK pin. If the output of the LM20143 is pre-biased at startup it will not sink current to pull the output low until the internal soft-start ramp exceeds the voltage at the feedback pin.The LM20143 is offered in a 16-pin eTSSOP package with an exposed pad that can be soldered to the PCB, eliminating the need for bulky heatsinks.Features■Input voltage range 2.95V to 5.5V■Accurate current limit minimizes inductor size■97% peak efficiency■Adjustable output voltage down to 0.8V■Adjustable switching frequency (500 kHz to 1.5 MHz)■32 mΩ integrated FET switches■Starts into prebiased loads■Output voltage tracking■Peak current mode control■Adjustable Soft-Start with external capacitor■Precision enable pin with hysteresis■Integrated OVP, UVLO, power good and thermal shutdown■eTSSOP-16 exposed pad package Applications■Simple to design, high efficiency point of load regulation from a 5V or 3.3V bus■High Performance DSPs, FPGAs, ASICs and microprocessors■Broadband, Networking and Optical Communications InfrastructureTypical Application Circuit30030501 PowerWise® is a registered trademark of National Semiconductor Corporation.© 2008 National Semiconductor LM20143 3A, PowerWise ® Adjustable Frequency Synchronous Buck RegulatorConnection Diagram30030502Top VieweTSSOP-16 PackageOrdering InformationOrder Number Package Type NSC Package DrawingPackage MarkingSupplied As LM20143MH eTSSOP-16MXA16A20143MH92 Units of Rail LM20143MHE 250 Units of Tape and Reel LM20143MHX2500 Units of Tape and ReelPin DescriptionsPin #Name Description1SS/TRKSoft-Start or Tracking control input. An internal 5 µA current source charges an external capacitor to set the Soft-Start ramp rate. If driven by a external source less than 800 mV, this pin overrides the internal reference that sets the output voltage. If left open, an internal 1ms Soft-Start ramp is activated.2FBFeedback input to the error amplifier from the regulated output. This pin is connected to the inverting input of the internal transconductance error amplifier. An 800 mV reference connected to the non-inverting input of the error amplifier sets the closed loop regulation voltage at the FB pin.3PGOOD Power good output signal. Open drain output indicating the output voltage is regulating within tolerance. is recommend for most applications.4COMP External compensation pin. Connect the compensation network to resistor and capacitor to this pin to compensate the device.5NC These pins must be connected to GND to ensure proper operation.6,7PVIN Input voltage to the power switches inside the device. These pins should be connected together at the device. A low ESR capacitor should be placed near these pins to stabilize the input voltage.8,9SW Switch pin. The PWM output of the internal power switches.10,11PGND Power ground pin for the internal power switches.12EN Precision enable input for the device. An external voltage divider can be used to set the device turn-on threshold. If not used the EN pin should be connected to PVIN.13VCC Internal 2.7V sub-regulator. This pin should be bypassed with a 1 µF ceramic capacitor.14AVIN Analog input supply that generates the internal bias. Must be connected to VIN through a low pass RC filter.15AGND Quiet analog ground for the internal bias circuitry.16RT Frequency adjust pin. Connecting a resistor on this pin to ground will set the oscillator frequency.EPExposed PadExposed metal pad on the underside of the package with a weak electrical connection to ground. It is recommended to connect this pad to the PC board ground plane in order to improve heat dissipation. 2L M 20143Absolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.Voltages from the indicated pins to GNDAVIN, PVIN, EN, PGOOD, SS/TRK, COMP, FB, RT-0.3V to +6V Storage Temperature-65°C to 150°C Junction Temperature150°CPower Dissipation (Note 2) 2.6W Lead Temperature (Soldering,10 sec)260°C Minimum ESD Rating (Note 3)±2kV Operating RatingsPVIN, AVIN to GND 2.95V to 5.5V Junction Temperature−40°C to + 125°CElectrical Characteristics Unless otherwise stated, the following conditions apply: AVIN = PVIN = VIN = 5V.Limits in standard type are for TJ = 25°C only, limits in bold face type apply over the junction temperature (TJ) range of -40°C to+125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ= 25°C, and are provided for reference purposes only.Symbol Parameter Conditions Min Typ Max UnitV FB Feedback pin voltage VIN= 2.95V to 5.5V0.7880.80.812VΔV OUT/ΔI OUT Load Regulation I OUT = 100 mA to 3A0.08%/AI CL Switch Current Limit Threshold VIN= 3.3V 4.3 4.8 5.3ARDS_ON High-Side Switch On Resistance ISW= 3.5A3655mΩRDS_ON Low-Side Switch On Resistance ISW= 3.5A3252mΩI Q Operating Quiescent Current Non-switching, VFB= VCOMP3.56mAI SD Shutdown Quiescent current VEN= 0V90180µAV UVLO VIN Under Voltage Lockout Rising VIN2.45 2.7 2.95VVUVLO_HYS VIN Under Voltage Lockout Hysteresis Falling VIN45100mVV VCC VCC Voltage IVCC= 0 µA 2.45 2.7 2.95VI SS Soft-Start Pin Source Current VSS/TRK= 0V2 4.57µAV TRACK SS/TRK Accuracy, VSS- VFBVSS/TRK= 0.4V-10315mVOscillatorF OSCH Oscillator Frequency RT= 49.9 kΩ135015001650kHzF OSCL Oscillator Frequency RT= 249 kΩ450510570kHzDCMAX Maximum Duty Cycle ILOAD= 0A85%TON_TIMEMinimum On Time100nsTCL_BLANK Current Sense Blanking Time After Rising VSW80nsError Amplifier and ModulatorI FB Feedback pin bias current VFB= 0.8V1100nAICOMP_SRC COMP Output Source Current VFB= VCOMP= 0.6V80100µAICOMP_SNK COMP Output Sink Current VFB= 1.0V, VCOMP= 0.6V80100µAGm Error Amplifier Transconductance ICOMP= ± 50 µA450510600µmhoAVOLError Amplifier Voltage Gain2000V/V Power GoodV OVP Over Voltage Protection Rising Threshold With respect to VFB105108111%VOVP_HYSOver Voltage Protection Hysteresis23%V PGTH PGOOD Rising Threshold With respect to VFB929496%VPGHYSPGOOD Falling Hysteresis23%TPGOODPGOOD deglitch time16µsI OL PGOOD Low Sink Current VPGOOD= 0.4V0.61mAI OH PGOOD High Leakage Current VPGOOD= 5V5100nALM20143Symbol ParameterConditionsMinTypMaxUnitEnableV IH_EN EN Pin turn-on Threshold V EN Rising 1.08 1.18 1.28V V EN_HYS EN Pin Hysteresis 66 mV Thermal ShutdownT SD Thermal Shutdown160 °C T SD_HYS Thermal Shutdown Hysteresis 10 °C Thermal ResistanceθJAJunction to Ambient38°C/WNote 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.Note 2:The maximum allowable power dissipation is a function of the maximum junction temperature, T J_MAX , the junctions-to-ambient thermal resistance, θJA ,and the ambient temperature, T A . The maximum allowable power dissipation at any ambient temperature is calculated using: P D_MAX = (T J_MAX – T A )/θJA . The maximum power dissipations of 2.6W is determined using T A = 25°C, θJA = 38°C/W, and T J_MAX = 125°C.Note 3:The human body model is a 100 pF capacitor discharged through a 1.5 k Ω resistor to each pin.Typical Performance CharacteristicsUnless otherwise specified: C IN = C OUT = 100 µF, L = 1.0 µH(Coilcraft MSS1038), V IN = 5V, V OUT = 1.2V, R LOAD = 1.2Ω, f SW = 1 MHz, T A = 25°C for efficiency curves, loop gain plots and waveforms, and T J = 25°C for all others.Efficiency vs. Load Current (V IN = 5V, f SW = 1.5 MHz)30030531Efficiency vs. Load Current (V IN = 3.3V, f SW = 1.5 MHz)30030530Efficiency vs. Load Current (V IN = 5V, f SW = 1.0 MHz)30030547Efficiency vs. Load Current (V IN = 3.3V, f SW = 1.0 MHz)30030546 4L M 20143Efficiency vs. Load Current (V IN = 5.0V, f SW = 500 kHz)30030549Efficiency vs. Load Current (V IN = 3.3V, f SW = 500 kHz)30030548High-Side FET Resistance vs. Temperature 30030557Low-Side FET Resistance vs. Temperature30030558Error Amplifier Gain vs. Frequency 30030536Line Regulation30030537LM20143Load Regulation30030538Feedback Pin Voltage vs. Temperature30030551Switching Frequency vs. Temperature30030539Switching Frequency vs. R T30030550Quiescent Current vs. V IN (Not Switching)30030540Shutdown Current vs. Temperature30030541 6L M 20143Enable Threshold vs. Temperature30030528UVLO Threshold vs. Temperature30030545Peak Current Limit vs. Temperature30030542Peak Current Limit vs. V OUT30030554Peak Current Limit vs. V IN30030555Load Transient Response30030534LM20143Line Transient Response30030543Start Up (Soft-Start)30030544Start Up (Tracking)30030533Short Circuit Input Current vs. V IN30030556Power Down30030532 8L M 20143Block Diagram30030503 LM20143Operation DescriptionGENERALThe LM20143 switching regulator features all of the functions necessary to implement an efficient low voltage buck regula-tor using a minimum number of external components. This easy to use regulator features two integrated switches and is capable of supplying up to 3A of continuous output current.The regulator utilizes peak current mode control with nonlin-ear slope compensation to optimize stability and transient response over the entire output voltage range. Peak current mode control also provides inherent line feed-forward, cycle-by-cycle current limiting and easy loop compensation. The switching frequency can be varied from 500 kHz to 1.5 MHz with an external resistor to ground. The device can operate at high switching frequency allowing use of a small inductor while still achieving efficiencies as high as 96%. The precision internal voltage reference allows the output to be set as low as 0.8V. Fault protection features include: current limiting,thermal shutdown, over voltage protection, and shutdown ca-pability. The device is available in the eTSSOP-16 package featuring an exposed pad to aid thermal dissipation. The LM20143 can be used in numerous applications to efficiently step-down from a 5V or 3.3V bus. The typical application cir-cuit for the LM20143 is shown in Figure 2 in the design guide.PRECISION ENABLEThe enable (EN) pin allows the output of the device to be en-abled or disabled with an external control signal. This pin is a precision analog input that enables the device when the volt-age exceeds 1.2V (typical). The EN pin has 100 mV of hys-teresis and will disable the output when the enable voltage falls below 1.1V (typical). If the EN pin is not used, it should be connected to VIN. Since the enable pin has a precise turn-on threshold it can be used along with an external resistor divider network from V IN to configure the device to turn-on at a precise input voltage. The precision enable circuitry will re-main active even when the device is disabled.PEAK CURRENT MODE CONTROLI n most cases, the peak current mode control architecture used in the LM20143 only requires two external components to achieve a stable design. The compensation can be select-ed to accommodate any capacitor type or value. The external compensation also allows the user to set the crossover fre-quency and optimize the transient performance of the device.For duty cycles above 50% all current mode control buck converters require the addition of an artificial ramp to avoid sub-harmonic oscillation. This artificial linear ramp is com-monly referred to as slope compensation. What makes the LM20143 unique is the amount of slope compensation will change depending on the output voltage. When operating at high output voltages the device will have more slope com-pensation than when operating at lower output voltages. This is accomplished in the LM20143 by using a non-linear parabolic ramp for the slope compensation. The parabolic slope compensation of the LM20143 is much better than the traditional linear slope compensation because it optimizes the stability of the device over the entire output voltage range.CURRENT LIMITThe precise current limit of the LM20143 is set at the factory to be within 10% over the entire operating temperature range.This enables the device to operate with smaller inductors that have lower saturation currents. When the peak inductor cur-rent reaches the current limit threshold, an over current event is triggered and the internal high-side FET turns off and thelow-side FET turns on allowing the inductor current to ramp down until the next switching cycle. For each sequential over-current event, the reference voltage is decremented and PWM pulses are skipped resulting in a current limit that does not aggressively fold back for brief over-current events, while at the same time providing frequency and voltage foldback protection during hard short circuit conditions.SOFT-START AND VOLTAGE TRACKINGThe SS/TRK pin is a dual function pin that can be used to set the start up time or track an external voltage source. The start up or Soft-Start time can be adjusted by connecting a capac-itor from the SS/TRK pin to ground. The Soft-Start feature allows the regulator output to gradually reach the steady state operating point, thus reducing stresses on the input supply and controlling start up current. If no Soft-Start capacitor is used the device defaults to the internal Soft-Start circuitry re-sulting in a start up time of approximately 1 ms. For applica-tions that require a monotonic start up or utilize the PGOOD pin, an external Soft-Start capacitor is recommended. The SS/TRK pin can also be set to track an external voltage source. The tracking behavior can be adjusted by two external resistors connected to the SS/TRK pin as shown in Figure 7.in the design guide.PRE-BIAS START UP CAPABILITYThe LM20143 is in a pre-biased state when the device starts up with an output voltage greater than zero. This often occurs in many multi-rail applications such as when powering an FP-GA, ASIC, or DSP. In these applications the output can be pre-biased through parasitic conduction paths from one sup-ply rail to another. Even though the LM20143 is a syn-chronous converter it will not pull the output low when a pre-bias condition exists. During start up the LM20143 will not sink current until the Soft-Start voltage exceeds the voltage on the FB pin. Since the device can not sink current it protects the load from damage that might otherwise occur if current is conducted through the parasitic paths of the load.POWER GOOD AND OVER VOLTAGE FAULT HANDLING The LM20143 has built in under and over voltage compara-tors that control the power switches. Whenever there is an excursion in output voltage above the set OVP threshold, the part will terminate the present on-pulse, turn-on the low-side FET, and pull the PGOOD pin low. The low-side FET will re-main on until either the FB voltage falls back into regulation or the zero cross detection is triggered which in turn tri-states the FETs. If the output reaches the UVP threshold the part will continue switching and the PGOOD pin will be asserted and go low. Typical values for the PGOOD resistor are on the or-der of 100 k Ω or less. To avoid false tripping during transient glitches the PGOOD pin has 16 µs of built in deglitch time to both rising and falling edges.UVLOThe LM20143 has a built-in under-voltage lockout protection circuit that keeps the device from switching until the input voltage reaches 2.7V (typical). The UVLO threshold has 45mV of hysteresis that keeps the device from responding to power-on glitches during start up. If desired the turn-on point of the supply can be changed by using the precision enable pin and a resistor divider network connected to V IN as shown in Figure 6. in the design guide.THERMAL PROTECTIONInternal thermal shutdown circuitry is provided to protect the integrated circuit in the event that the maximum junction tem-10L M 20143perature is exceeded. When activated, typically at 160°C, the LM20143 tri-states the power FETs and resets soft start. After the junction cools to approximately 150°C, the part starts up using the normal start up routine. This feature is provided to prevent catastrophic failures from accidental device over-heating.LIGHT LOAD OPERATIONThe LM20143 offers increased efficiency when operating at light loads. Whenever the load current is reduced to a point where the peak to peak inductor ripple current is greater than two times the load current, the part will enter the diode emu-lation mode preventing significant negative inductor current.The point at which this occurs is the critical conduction bound-ary and can be calculated by the following equation:Several diagrams are shown in Figure 1 illustrating continu-ous conduction mode (CCM), discontinuous conduction mode, and the boundary condition.It can be seen that in diode emulation mode, whenever the inductor current reaches zero the SW node will become high impedance. Ringing will occur on this pin as a result of the LC tank circuit formed by the inductor and the parasitic capaci-tance at the node. If this ringing is of concern an additional RC snubber circuit can be added from the switch node to ground.At very light loads, usually below 100 mA, several pulses may be skipped in between switching cycles, effectively reducing the switching frequency and further improving light-load effi-ciency.30030505FIGURE 1. Modes of Operation for LM20143LM20143Design GuideThis section walks the designer through the steps necessaryto select the external components to build a fully functionalpower supply. As with any DC-DC converter numerous trade-offs are possible to optimize the design for efficiency, size, orperformance. These will be taken into account and highlight-ed throughout this discussion. To facilitate component selec-tion discussions the circuit shown in Figure 2 below may beused as a reference. Unless otherwise indicated all formulasassume units of amps (A) for current, farads (F) for capaci-tance, henries (H) for inductance and volts (V) for voltages.30030523FIGURE 2. Typical Application CircuitThe first equation to calculate for any buck converter is duty-cycle. Ignoring conduction losses associated with the FETsand parasitic resistances it can be approximated by:INDUCTOR SELECTION (L)The inductor value is determined based on the operating fre-quency, load current, ripple current, and duty cycle.The inductor selected should have a saturation current ratinggreater than the peak current limit of the device. Keep in mindthe specified current limit does not account for delay of thecurrent limit comparator, therefore the current limit in the ap-plication may be higher than the specified value. To optimizethe performance and prevent the device from entering currentlimit at maximum load, the inductance is typically selectedsuch that the ripple current, ΔiL, is less than 30% of the ratedoutput current. Figure 3, shown below illustrates the switchand inductor ripple current waveforms. Once the input volt-age, output voltage, operating frequency, and desired ripplecurrent are known, the minimum value for the inductor can becalculated by the formula shown below:30030509FIGURE 3. Switch and Inductor Current WaveformsIf needed, slightly smaller value inductors can be used, how-ever, the peak inductor current, IOUT+ Δi L/2, should be keptbelow the peak current limit of the device. In general, the in-ductor ripple current, ΔiL, should be greater than 10% of therated output current to provide adequate current sense infor-mation for the current mode control loop. If the ripple currentin the inductor is too low, the control loop will not have suffi-cient current sense information and can be prone to instability.OUTPUT CAPACITOR SELECTION (COUT)The output capacitor, COUT, filters the inductor ripple currentand provides a source of charge for transient load conditions.A wide range of output capacitors may be used with theLM20143 that provide excellent performance. The best per-formance is typically obtained using ceramic, SP, or OSCONtype chemistries. Typical trade-offs are that the ceramic ca-pacitor provides extremely low ESR to reduce the outputripple voltage and noise spikes, while the SP and OSCONcapacitors provide a large bulk capacitance in a small volumefor transient loading conditions.When selecting the value for the output capacitor the two per-formance characteristics to consider are the output voltageripple and transient response. The output voltage ripple canbe approximated by using the formula shown below.Where, ΔVOUT(V) is the amount of peak to peak voltage rippleat the power supply output, RESR(Ω) is the series resistanceof the output capacitor, fSW(Hz) is the switching frequency,and COUT(F) is the output capacitance used in the design.The amount of output ripple that can be tolerated is applica-tion specific; however a general recommendation is to keepthe output ripple less than 1% of the rated output voltage.Keep in mind ceramic capacitors are sometimes preferredbecause they have very low ESR; however, depending onpackage and voltage rating of the capacitor the value of thecapacitance can drop significantly with applied voltage. Theoutput capacitor selection will also affect the output voltagedroop during a load transient. The peak droop on the outputvoltage during a load transient is dependent on many factors;however, an approximation of the transient droop ignoringloop bandwidth can be obtained using the following equation.12LM2143Where, COUT(F) is the minimum required output capacitance,L (H) is the value of the inductor, VDROOP(V) is the outputvoltage drop ignoring loop bandwidth considerations, ΔIOUT-STEP(A) is the load step change, RESR(Ω) is the outputcapacitor ESR, VIN(V) is the input voltage, and VOUT(V) isthe set regulator output voltage. Both the tolerance and volt-age coefficient of the capacitor needs to be examined whendesigning for a specific output ripple or transient drop target.INPUT CAPACITOR SELECTION (CIN)Good quality input capacitors are necessary to limit the ripplevoltage at the VIN pin while supplying most of the switch cur-rent during the on-time. In general it is recommended to usea ceramic capacitor for the input as they provide both a lowimpedance and small footprint. One important note is to usea good dielectric for the ceramic capacitor such as X5R orX7R. These provide better over temperature performanceand also minimize the DC voltage derating that occurs on Y5Vcapacitors. For most applications, a 22 µF, X5R, 6.3V inputcapacitor is sufficient; however, additional capacitance maybe required if the connection to the input supply is far from thePVIN pins. The input capacitor should be placed as close aspossible PVIN and PGND pins of the device.Non-ceramic input capacitors should be selected for RMScurrent rating and minimum ripple voltage. A good approxi-mation for the required ripple current rating is given by therelationship:As indicated by the RMS ripple current equation, highest re-quirement for RMS current rating occurs at 50% duty cycle.For this case, the RMS ripple current rating of the input ca-pacitor should be greater than half the output current. For bestperformance, low ESR ceramic capacitors should be placedin parallel with higher capacitance capacitors to provide thebest input filtering for the device.SETTING THE OUTPUT VOLTAGE (RFB1, RFB2)The resistors RFB1and RFB2are selected to set the outputvoltage for the device. Table 1, shown below, provides sug-gestions for RFB1and RFB2for common output voltages.TABLE 1. Suggested Values for RFB1and RFB2RFB1(kΩ)RFB2(kΩ)V OUTshort open0.84.9910 1.28.8710.2 1.512.710.2 1.821.510.2 2.531.610.2 3.3If different output voltages are required, RFB2should be se-lected to be between 4.99 kΩ to 49.9 kΩ and RFB1can becalculated using the equation below.ADJUSTING THE OPERATING FREQUENCY (RT)The operating frequency of the LM20143 can be adjusted byconnecting a resistor from the RT pin to ground. The equationshown below can be used to calculate the value of RTfor agiven operating frequency.Where, fSWis the switching frequency in kHz, and RTis thefrequency adjust resistor in kΩ. Please refer to the curve Os-cillator Frequency verses RTin the typical performance char-acteristics section. If the RTresistor is omitted the device willnot operate.LOOP COMPENSATION (RC1, CC1)The purpose of loop compensation is to meet static and dy-namic performance requirements while maintaining adequatestability. Optimal loop compensation depends on the outputcapacitor, inductor, load, and the device itself. Table 2 belowgives values for the compensation network that will result ina stable system when using a 100 µF, 6.3V ceramic X5R out-put capacitor and 1 µH inductor.TABLE 2. Recommended Compensation forCOUT= 100 µF, L = 1 µH & fSW= 1 MHzVINVOUTCC1(nF)RC1(kΩ)5.00 3.30 4.717.85.00 2.50 4.712.15.00 1.80 4.77.685.00 1.50 4.7 5.95.00 1.20 4.7 3.575.000.80 4.7 1.583.30 2.504.7133.30 1.804.79.763.30 1.504.7 6.493.30 1.204.7 4.643.300.804.7 1.58If the desired solution differs from the table above the looptransfer function should be analyzed to optimize the loopcompensation. The overall loop transfer function is the prod-uct of the power stage and the feedback network transferfunctions. For stability purposes, the objective is to have aloop gain slope that is -20db/decade from a very low frequen-cy to beyond the crossover frequency. Figure 4, shown below,shows the transfer functions for power stage, feedback/com-pensation network, and the resulting closed loop system forthe LM20143.LM20143。

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