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1、 2004 National Semiconductor CorporationDS200309LP3853/LP3856 3A Fast Ultra Low Dropout Linear RegulatorsMarch 2004LP3853/LP38563A Fast Response Ultra Low Dropout Linear RegulatorsGeneral DescriptionFeaturesThe LP3853/LP3856 series of fast ultra low-dropout linearn Ultra low dropout

2、voltageregulators operate from a +2.5V to +7.0V input supply. Widen Stable with selected ceramic capacitors range of preset output voltage options are available. Thesen Low ground pin currentultra low dropout linear regulators respond very quickly ton Load regulation of 0.08%step changes in load, wh

3、ich makes them suitable for lown 10nA quiescent current in shutdown mode voltage microprocessor applications. The LP3853/LP3856n Guaranteed output current of 3A DCare developed on a CMOS process which allows low quies-cent current operation independent of output load current.n Available in TO-263 an

4、d TO-220 packages This CMOS process also allows the LP3853/LP3856 to op-n Output voltage accuracy 1.5%erate under extremely low dropout conditions.n Error flag indicates output statusDropout Voltage: Ultra low dropout voltage; typically 39mVn Sense option improves load regulation at 300mA load curre

5、nt and 390mV at 3A load current.n Overtemperature/overcurrent protectionGround Pin Current: Typically 4mA at 3A load current.n 40C to +125C junction temperature rangeShutdown Mode: Typically 10nA quiescent current whenApplicationsthe shutdown pin is pulled low.Error Flag: Error flag goes low when th

6、e output voltagen Microprocessor power supplies drops 10% below nominal value.n Stable with ceramic output capacitorsSENSE: Sense pin improves regulation at remote loads.n GTL, GTL+, BTL, and SSTL bus terminatorsPrecision Output Voltage: Multiple output voltage optionsn Power supplies for DSPs are a

7、vailable ranging from 1.8V to 5.0V with a guaranteedn SCSI terminator accuracy of 1.5% at room temperature, and 3.0% over alln Post regulatorsconditions (varying line, load, and temperature).n High efficiency linear regulatorsn Battery chargersn Other battery powered applicationsTypical Application

8、Circuits20030901*SD and ERROR pins must be pulled high through a 10kW pull-up resistor. Connect the ERROR pin to ground if this function is not used. See Application Hints for more 2LP3853/LP3856Typical Application Circuits (Continued)20030934*SD pin must be pulled high t

9、hrough a 10kW pull-up resistor. See Application Hints for more information.Connection Diagrams2003090520030906Top ViewTop ViewTO220-5 PackageTO263-5 PackageBent, Staggered LeadsPin Description for TO220-5 and TO263-5 PackagesPin #LP3853LP3856NameFunctionNameFunction1SDShutdownSDShutdown2VINInput Sup

10、plyVINInput Supply3GNDGroundGNDGround4VOUTOutput VoltageVOUTOutput Voltage5ERRORERROR FlagSENSERemote Sense PLP3853/LP3856Ordering Information20030931Package Type Designator is T for TO220 package, and S for TO263 package.TABLE 1. Package Marking and Ordering InformationOutput Vol

11、tageOrder NumberDescription (Current, Option)Package TypePackage MarkingSupplied As:5.0LP3853ES-5.03A, Error FlagTO263-5LP3853ES-5.0Rail5.0LP3853ESX-5.03A, Error FlagTO263-5LP3853ES-5.0Tape and Reel3.3LP3853ES-3.33A, Error FlagTO263-5LP3853ES-3.3Rail3.3LP3853ESX-3.33A, Error FlagTO263-5LP3853ES-3.3T

12、ape and Reel2.5LP3853ES-2.53A, Error FlagTO263-5LP3853ES-2.5Rail2.5LP3853ESX-2.53A, Error FlagTO263-5LP3853ES-2.5Tape and Reel1.8LP3853ES-1.83A, Error FlagTO263-5LP3853ES-1.8Rail1.8LP3853ESX-1.83A, Error FlagTO263-5LP3853ES-1.8Tape and Reel5.0LP3856ES-5.03A, SENSETO263-5LP3856ES-5.0Rail5.0LP3856ESX-

13、5.03A, SENSETO263-5LP3856ES-5.0Tape and Reel3.3LP3856ES-3.33A, SENSETO263-5LP3856ES-3.3Rail3.3LP3856ESX-3.33A, SENSETO263-5LP3856ES-3.3Tape and Reel2.5LP3856ES-2.53A, SENSETO263-5LP3856ES-2.5Rail2.5LP3856ESX-2.53A, SENSETO263-5LP3856ES-2.5Tape and Reel1.8LP3856ES-1.83A, SENSETO263-5LP3856ES-1.8Rail1

14、.8LP3856ESX-1.83A, SENSETO263-5LP3856ES-1.8Tape and Reel5.0LP3853ET-5.03A, Error FlagTO220-5LP3853ET-5.0Rail3.3LP3853ET-3.33A, Error FlagTO220-5LP3853ET-3.3Rail2.5LP3853ET-2.53A, Error FlagTO220-5LP3853ET-2.5Rail1.8LP3853ET-1.83A, Error FlagTO220-5LP3853ET-1.8Rail5.0LP3856ET-5.03A, SENSETO220-5LP385

15、6ET-5.0Rail3.3LP3856ET-3.33A, SENSETO220-5LP3856ET-3.3Rail2.5LP3856ET-2.53A, SENSETO220-5LP3856ET-2.5Rail1.8LP3856ET-1.83A, SENSETO220-5LP3856ET-1.8R4LP3853/LP3856Block DiagramsLP385320030903LP3856200309295LP3853/LP3856Absolute Maximum Ratings (Note 1)IOUT (Surviva

16、l)Short Circuit ProtectedIf Military/Aerospace specified devices are required,Maximum Voltage for ERRORplease contact the National Semiconductor Sales Office/PinVINDistributors for availability and specifications.Maximum Voltage for SENSE PinVOUTStorage Temperature Range65C to +150CLead TemperatureO

17、perating Ratings(Soldering, 5 sec.)260CESD Rating (Note 3)2 kVInput Supply Voltage (Note 11)2.5V to 7.0V Power Dissipation (Note 2)Internally LimitedShutdown Input Voltage0.3V to 7.0V Input Supply Voltage (Survival)0.3V to +7.5VMaximum Operating Current (DC)3A Shutdown Input VoltageJunction Temperat

18、ure40C to +125C(Survival)0.3V to 7.5VOutput Voltage (Survival), (Note6), (Note 7)0.3V to +6.0VElectrical Characteristics LP3853/LP3856Limits in standard typeface are for TJ = 25C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) +

19、 1V, IL = 10 mA, COUT = 10F, VSD = 2V.SymbolParameterConditionsTyp (Note 4)LP3853/6 (Note 5)UnitsMinMaxVOOutput Voltage Tolerance (Note 8)VOUT +1V VIN 7.0V 10 mA IL 3A0-1.5-3.0+1.5+3.0%DV OLOutput Voltage Line Regulation (Note 8)VOUT +1V VIN 7.0V0.020.06%DVO/ DIOUTOutput Voltage Load Regulation(Note

20、 8)10 mA IL 3A0.080.14%VIN - VOUTDropout Voltage (Note 10)IL = 300 mA395065mVIL = 3A390450600IGNDGround Pin Current In Normal Operation ModeIL = 300 mA4910mAIL = 3A4910IGNDGround Pin Current In Shutdown ModeVSD 0.3V0.0110A-40C TJ 85C50IO(PK)Peak Output CurrentVO VO(NOM) - 4%4.5AShort Circuit Protect

21、ionISCShort Circuit Current6A6LP3853/LP3856Electrical Characteristics LP3853/LP3856 (Continued)Limits in standard typeface are for TJ = 25C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) + 1V, IL = 10 mA, COUT =

22、 10F, VSD = 2V.SymbolParameterConditionsTyp (Note 4)LP3853/6 (Note 5)UnitsMinMaxShutdown InputVSDTShutdown ThresholdOutput = HighVIN2VOutput = Low00.3TdOFFTurn-off delayIL = 3A20sTdONTurn-on delayIL = 3A25sISDSD Input CurrentVSD = VIN1nAError FlagVTThreshold(Note 9)10516%VTHThreshold Hysteresis(Note

23、 9)528%VEF(Sat)Error Flag SaturationIsink = 100A0.020.1VTdFlag Reset Delay1sIlkError Flag Pin Leakage Current1nAImaxError Flag Pin Sink CurrentVError = 0.5V1mAAC ParametersPSRRRipple RejectionVIN = VOUT + 1V COUT = 10uFVOUT = 3.3V, f = 120Hz73dBVIN = VOUT + 0.5V COUT = 10uFVOUT = 3.3V, f = 120Hz57rn

24、(l/fOutput Noise Densityf = 120Hz0.8VenOutput Noise VoltageBW = 10Hz 100kHz VOUT = 2.5V150V (rms)BW = 300Hz 300kHz VOUT = 2.5V100Note 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

25、functional, but does not guarantee specific performance limits. For guaranteed specifications and test conditions, see Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated und

26、er the listed test conditions.Note 2: At elevated temperatures, devices must be derated based on package thermal resistance. The devices in TO220 package must be derated at qjA = 50C/W (with 0.5in2, 1oz. copper area), junction-to-ambient (with no heat sink). The devices in the TO263 surface-mount pa

27、ckage must be derated at qjA = 60C/W (with 0.5in2, 1oz. copper area), junction-to-ambient. See Application Hints.Note 3: The human body model is a 100pF capacitor discharged through a 1.5kW resistor into each pin.Note 4: Typical numbers are at 25C and represent the most likely parametric norm.Note 5

28、: Limits are guaranteed by testing, design, or statistical correlation.Note 6: If used in a dual-supply system where the regulator load is returned to a negative supply, the output must be diode-clamped to ground.Note 7: The output PMOS structure contains a diode between the VIN and VOUT terminals.

29、This diode is normally reverse biased. This diode will get forward biased if the voltage at the output terminal is forced to be higher than the voltage at the input terminal. This diode can typically withstand 200mA of DC current and 1Amp of peak current.Note 8: Output voltage line regulation is def

30、ined as the change in output voltage from the nominal value due to change in the input line voltage. Output voltage load regulation is defined as the change in output voltage from the nominal value due to change in load current. The line and load regulation specification contains only the typical nu

31、mber. However, the limits for line and load regulation are included in the output voltage tolerance specification.Note 9: Error Flag threshold and hysteresis are specified as percentage of regulated output voltage. See Application Hints.Note 10: Dropout voltage is defined as the minimum input to out

32、put differential voltage at which the output drops 2% below the nominal value. Dropout voltage specification applies only to output voltages of 2.5V and above. For output voltages below 2.5V, the drop-out voltage is nothing but the input to output differential, since the minimum input voltage is 2.5

33、V.Note 11: The minimum operating value for VIN is equal to either VOUT(NOM) + VDROPOUT or 2.5V, whichever is LP3853/LP3856Typical Performance Characteristics Unless otherwise specified: TJ = 25C, COUT = 10F, CIN = 10F, S/D pin is tied to VIN, VOUT = 2.5V, VIN = VO(NOM) + 1V,

34、 IL = 10 mA.Ground Current vs Output Load CurrentDropout Voltage vs Output Load CurrentVOUT = 5V2003096220030953Ground Current vs Output VoltageIL = 3AShutdown IQ vs Junction Temperature2003095520030954Errorflag Threshold vs Junction TemperatureDC Load Reg. vs Junction Temperature2003095720030958www

35、.8LP3853/LP3856Typical Performance Characteristics Unless otherwise specified: TJ = 25C, COUT = 10F, CIN = 10F, S/D pin is tied to VIN, VOUT = 2.5V, VIN = VO(NOM) + 1V, IL = 10 mA. (Continued)DC Line Regulation vs TemperatureVIN vs VOUT Over Temperature2003096020030959Load Transient Resp

36、onseNoise vs FrequencyCIN = COUT = 10F, OSCON2003097120030961Load Transient ResponseLoad Transient ResponseCIN = COUT = 100F, OSCONCIN = COUT = 100F, POSCAP20030972200309739LP3853/LP3856Typical Performance Characteristics Unless otherwise specified: TJ = 25C, COUT = 10F, CIN = 10F, S

37、/D pin is tied to VIN, VOUT = 2.5V, VIN = VO(NOM) + 1V, IL = 10 mA. (Continued)Load Transient ResponseLoad Transient ResponseCIN = COUT = 10F, TANTALUMCIN = COUT = 100F, TANTALUM2003097420030975Load Transient ResponseLoad Transient ResponseCIN = COUT = 10F, OSCONCIN = COUT = 100F, OSCON2003097620030

38、977Load Transient ResponseLoad Transient ResponseCIN = COUT = 100F, POSCAPCIN = COUT = 10F, TANTALUM200309782003097910LP3853/LP3856Typical Performance Characteristics Unless otherwise specified: TJ = 25C, COUT = 10F, CIN = 10F, S/D pin is tied to VIN, VOUT = 2.5V, VIN = VO(NOM) + 1V,

39、 IL = 10 mA. (Continued)Load Transient ResponseLoad Transient ResponseCIN = 4 x 10F CERAMIC CIN = COUT = 100F, TANTALUMCOUT = 3 x 10F CERAMIC2003098020030981Load Transient ResponseLoad Transient ResponseCIN = 4 x 10F CERAMICCIN = 2 x 10F CERAMICCOUT = 3 x 10F CERAMICCOUT = 2 x 10F CERAMIC20030982200

40、30983Load Transient Response CIN = 2 x 10F CERAMIC COUT = 2 x 10F CERAMIC2003098411LP3853/LP3856Application HintsVIN RESTRICTIONS FOR PROPER START-UPOPERATION WITH CERAMIC OUTPUT CAPACITORSTo prevent misoperation, ensure that VIN is below 50mVLP385X voltage regulators can operate wit

41、h ceramic output before start-up is initiated. This scenario can occur in sys-capacitors if the values of input and output capacitors are tems with a backup battery using reverse-biased blockingselected appropriately. The total ceramic output capacitance diodes which may allow enough leakage current

42、 to flow intomust be equal to or less than a specified maximum value in the VIN node to raise its voltage slightly above ground whenorder for the regulator to remain stable over all operating the main power is removed. Using low leakage diodes or aconditions. This maximum amount of ceramic output ca

43、paci- resistive pull down can prevent the voltage at VIN from risingtance is dependent upon the amount of ceramic input ca- above 50mV. Large bulk capacitors connected to VIN maypacitance used as well as the load current of the application. also cause a start-up problem if they do not discharge full

44、yThis relationship is shown in Figure 2, which graphs the before re-start is initiated (but only if VIN is allowed to fallmaximum stable value of ceramic output capacitance as a below 1V). A resistor connected across the capacitor willfunction of ceramic input capacitance for load currents of 1A, al

45、low it to discharge more quickly. It should be noted that the2A, and 3A. For example, if the maximum load current is 1A, probability of a false start caused by incorrect logic statesa 10F ceramic input capacitor will allow stable operation for is extremely low.values of ceramic output capacitance fr

46、om 10F up to about500F.EXTERNAL CAPACITORSLike any low-dropout regulator, external capacitors are re- quired to assure stability. These capacitors must be correctly selected for proper performance.INPUT CAPACITOR: An input capacitor of at least 10F is required. Ceramic or Tantalum may be used, and c

47、apaci- tance may be increased without limitOUTPUT CAPACITOR: An output capacitor is required for loop stability. It must be located less than 1 cm from the device and connected directly to the output and ground pins using traces which have no other currents flowing through them (see PCB Layout secti

48、on).The minimum amount of output capacitance that can be used for stable operation is 10F. For general usage across all load currents and operating conditions, the part was characterized using a 10F Tantalum input capacitor. The minimum and maximum stable ESR range for the output capacitor was then

49、measured which kept the device stable,assuming any output capacitor whose value is greater than2003098510F (see Figure 1 below).FIGURE 2. Maximum Ceramic Output Capacitance vs Ceramic Input CapacitanceIf the maximum load current is 2A and a 10F ceramic input capacitor is used, the regulator will be

50、stable with ceramic output capacitor values from 10F up to about 50F. At 3A of load current, the ratio of input to output capacitance required approaches 1:1, meaning that whatever amount of ceramic output capacitance is used must also be provided at the input for stable operation. For load currents

51、 between 1A, 2A, and 3A, interpolation may be used to approximate values on the graph. When calculating the total ceramic output capaci- tance present in an application, it is necessary to include any ceramic bypass capacitors connected to the regulator out- put.SELECTING A CAPACITORIt is important

52、to note that capacitance tolerance and varia- 20030970tion with temperature must be taken into consideration when selecting a capacitor so that the minimum required amountFIGURE 1. ESR Curve for COUT (with10F Tantalumof capacitance is provided over the full operating tempera- Input Capacitor)ture ra

53、nge. In general, a good Tantalum capacitor will show very little capacitance variation with temperature, but a ce-It should be noted that it is possible to operate the part withramic may not be as good (depending on dielectric type).an output capacitor whose ESR is below these limits, as-Aluminum electrolytics also typically have large tem