LM22676中文资料

November 21, 2008

LM226763A SIMPLE SWITCHER®, Step-Down Voltage Regulatorwith Precision EnableGeneral DescriptionThe LM22676 series of regulators are monolithic integratedcircuits which provide all of the active functions for a step-down (buck) switching regulator capable of driving up to 3Aloads with excellent line and load regulation characteristics.High efficiency (>90%) is obtained through the use of a lowON-resistance N-channel MOSFET. The series consists of afixed 5V output and an adjustable version.The SIMPLE SWITCHER® concept provides for an easy touse complete design using a minimum number of externalcomponents and National’s WEBENCH® design tool.National’s WEBENCH® tool includes features such as exter-nal component calculation, electrical simulation, thermal sim-ulation, and Build-It boards for easy design-in. The switchingclock frequency is provided by an internal fixed frequency os-cillator which operates at 500 kHz. The LM22676 series alsohas built in thermal shutdown, current limiting and an enablecontrol input that can power down the regulator to a low 25µA quiescent current standby condition.Features■Wide input voltage range: 4.5V to 42V■Internally compensated voltage mode control■Stable with low ESR ceramic capacitors■120 mΩ N-channel MOSFET TO-263 THIN package■100 mΩ N-channel MOSFET PSOP-8 package■Output voltage options: -ADJ (outputs as low as 1.285V) -5.0 (output fixed to 5V)■±1.5% feedback reference accuracy■Switching frequency of 500 kHz■-40°C to 125°C operating junction temperature range■Precision enable pin■Integrated boot diode■Integrated soft-start■Fully WEBENCH® enabled■Step-down and inverting buck-boost applicationsPackage■PSOP-8 (Exposed Pad)■TO-263 THIN (Exposed Pad)Applications■Industrial Control■Telecom and Datacom Systems■Embedded Systems■Automotive Telematics and Body Electronics■Conversions from Standard 24V, 12V and 5V Input RailsSimplified Application Schematic

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© 2008 National Semiconductor Corporation300765www.national.comLM22676 3A SIMPLE SWITCHER®, Step-Down Voltage Regulator with Precision Enable元器件交易网www.cecb2b.comConnection Diagrams

300765408-Lead Plastic PSOP-8 PackageNS Package Number MRA08B

300765027-Lead Plastic TO-263 THIN PackageNS Package Number TJ7AOrdering InformationOutput VoltageOrder NumberPackage TypeNSC Package DrawingSupplied AsADJLM22676MR-ADJPSOP-8 Exposed PadMRA08B95 Units in RailsADJLM22676MRE-ADJ250 Units in Tape and ReelADJLM22676MRX-ADJ2500 Units in Tape and ReelADJLM22676TJE-ADJTO-263 THIN Exposed PadTJ7A250 Units in Tape and ReelADJLM22676TJ-ADJ1000 Units in Tape and Reel5.0LM22676MR-5.0PSOP-8 Exposed PadMRA08B95 Units in Rails5.0LM22676MRE-5.0250 Units in Tape and Reel5.0LM22676MRX-5.02500 Units in Tape and Reel5.0LM22676TJE-5.0TO-263 THIN Exposed PadTJ7A250 Units in Tape and Reel5.0LM22676TJ-5.01000 Units in Tape and Reel

www.national.com2LM22676元器件交易网www.cecb2b.comPin DescriptionsPin NumbersPSOP-8PackagePin NumbersTO-263 THINPackageNameDescriptionApplication Information

13BOOTBootstrap inputProvides the gate voltage for the high side NFET.2, 35NCNot ConnectedPins are not electrically connected inside the chip. Pins dofunction as thermal conductor.46FBFeedback pinInverting input to the internal voltage error amplifier.57ENPrecision enable pinWhen pulled low regulator turns off.64GNDSystem groundProvide good capacitive decoupling between VIN and thispin72VINSource input voltageInput to the regulator. Operates from 4.5V to 42V.81SWSwitch pinAttaches to the switch node

3www.national.comLM22676元器件交易网www.cecb2b.comAbsolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.VIN to GND43VEN Pin Voltage-0.5V to 6VSW to GND (Note 2)-5V to VINBOOT Pin VoltageVSW + 7VFB Pin Voltage-0.5V to 7VPower DissipationInternally LimitedJunction Temperature150°CSoldering Information Infrared (5 sec.)260°CESD Rating (Note 3) Human Body Model±2 kVStorage Temperature Range-65°C to +150°COperating Ratings (Note 1)Supply Voltage (VIN)4.5V to 42VJunction Temperature Range-40°C to +125°CElectrical Characteristics Limits in standard type are for TJ = 25°C only; limits in boldface type apply over thejunction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statisticalcorrelation. Typical values represent the most likely parametric norm at TA = TJ = 25°C, and are provided for reference purposesonly. Unless otherwise specified: VIN = 12V.SymbolParameterConditionsMin(Note 5)Typ(Note 4)Max(Note 5)UnitsLM22676-5.0VFBFeedback VoltageVIN = 8V to 42V4.925/4.95.05.075/5.1VLM22676-ADJVFBFeedback VoltageVIN = 4.7V to 42V1.266/1.2591.2851.304/1.311VAll Output Voltage VersionsIQQuiescent CurrentVFB = 5V 3.46mAISTDBYStandby Quiescent CurrentEN Pin = 0V 2540µAICLCurrent Limit 3.4/3.354.25.3/5.5AILOutput Leakage CurrentVIN = 42V, EN Pin = 0V, VSW = 0V 0.22µAVSW = -1V 0.13µARDS(ON)Switch On-ResistanceTO-263 THIN Package 0.120.16/0.22ΩPSOP-8 Package 0.100.16/0.20fOOscillator Frequency 400500600kHzTOFFMINMinimum Off-time 300 nsTONMINMinimum On-time 100 nsIBIASFeedback Bias CurrentVFB = 1.3V (ADJ Version Only) 230 nAVENEnable Threshold Voltage 1.31.61.9VIENEnable Input CurrentEN Input = 0V 6 µATSDThermal ShutdownThreshold 150 °CθJAThermal ResistanceTJ Junction to ambient temperatureresistance (Note 6) 22 °C/WθJAThermal ResistanceMR Package, Junction to ambienttemperature resistance (Note 7) 60 °C/W