LM2575

LM2575MicrelLM257552kHz Simple 1A Buck RegulatorGeneral DescriptionThe LM2575 series of monolithic integrated circuits provideall the active functions for a step-down (buck) switchingregulator. Fixed versions are available with a 3.3V, 5V, 12V,fixed output. Adjustable versions have an output voltagerange from 1.23V to 37V. Both versions are capable of drivinga 1A load with excellent line and load regulation.These regulators are simple to use because they require aminimum number of external components and include internalfrequency compensation and a fixed-frequency oscillator.The LM2575 series offers a high efficiency replacement forpopular three-terminal adjustable linear regulators. Itsubstantially reduces the size of the heat sink, and in manycases no heat sink is required.A standard series of inductors available from several differentmanufacturers are ideal for use with the LM2575 series. Thisfeature greatly simplifies the design of switch-mode powersupplies.The feedback voltage is guaranteed to ±2% tolerance foradjustable versions, and the output voltage is guaranteed to±3% for fixed versions, within specified input voltages andoutput load conditions. The oscillator frequency is guaranteedto ±10%. External shutdown is included, featuring less than200µA standby current. The output switch includes cycle-by-cycle current limiting and thermal shutdown for full protectionunder fault conditions.Features•3.3V, 5V, 12V, and adjustable output versions•Voltage over specified line and load conditions:Fixed version: ±3% max. output voltageAdjustable version: ±2% max. feedback voltage•Guaranteed 1A output current•Wide input voltage range:4V to 40V•Wide output voltage range1.23V to 37V•Requires only 4 external components•52kHz fixed frequency internal oscillator•Low power standby mode IQ typically < 200µA•80% efficiency (adjustable version typically > 80%)•Uses readily available standard inductors•Thermal shutdown and current limit protection•100% electrical thermal limit burn-inApplications•••••Simple high-efficiency step-down (buck) regulatorEfficient pre-regulator for linear regulatorsOn-card switching regulatorsPositive to negative converter (inverting Buck-Boost)Isolated Flyback Converter using minimum number ofexternal components•Negative Boost ConverterTypical Applications870 207V–40VUnregulatedDC Input14Feedback+VINCIN100µF+LM2575-5.0OutputL12330µH D11N5822++5V, 1ARegulatedOutput7V–40VUnregulatedDC Input14LM2575Feedback+VIN+CIN100µF35GndOn/OffCOUT330µF35GndOn/OffOutputL12330µH D11N5822+5V, 1ARegulatedOutput+COUT330µFR2 3.09kR1 1kNote: Pin numbers are for TO-220 PackageNote: Pin numbers are for TO-220 PackageVOUT = 1.23 1 +R2R1( )Fixed Regulator in Typical ApplicationAdjustable Regulator in Fixed Output ApplicationAugust 19991M2575

LM2575MicrelOrdering InformationPart Number‡LM2575BN*LM2575-3.3BNLM2575-5.0BNLM2575-12BNLM2575BWM*LM2575-3.3BWMLM2575-5.0BWMLM2575-12BWMLM2575BT*†LM2575-3.3BT†LM2575-5.0BT†LM2575-12BT†LM2575BU*LM2575-3.3BULM2575-5.0BULM2575-12BUTemperature Range–40°C to +85 °C–40°C to +85 °C–40°C to +85 °C–40°C to +85 °C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°C–40°C to +85°CPackage16-pin Plastic DIP16-pin Plastic DIP16-pin Plastic DIP16-pin Plastic DIP24-pin Wide SOIC24-pin Wide SOIC24-pin Wide SOIC24-pin Wide SOIC5-lead TO-2205-lead TO-2205-lead TO-2205-lead TO-2205-lead TO-2635-lead TO-2635-lead TO-2635-lead TO-263* Adjustable output regulators.† Contact factory for bent or staggered leads option.Pin Configurations5-LEAD TO-220 (T)GND5- ON/OFF4- FEEDBACK3- GROUND2- OUTPUT1- VINGND5-LEAD TO-263 (U)5- ON/OFF4- FEEDBACK3- GROUND2- OUTPUT1- VIN24-LEAD SOIC (WM)16-LEAD DIP (N)NCNCOUTPUTNCGNDNCFBNC12345678161514131211109VINNCGNDGNDGNDGNDNCON/OFFPWR GNDNCNCNCNCNCFBSIG GNDNCON/OFFNCPWR GND1234567101112242322212019181716151413NCNCNCNCNCNCOUTPUTOUTPUTNCVINVINNCLM25752August 1999

LM2575Micrel Absolute Maximum Ratings (Note 1)

Maximum Supply VoltageON/OFF Pin Input Voltage

Output Voltage to Ground (Steady State)Power Dissipation

Storage Temperature RangeMinimum ESD RatingC = 100pF, R = 1.5kΩFB Pin

Lead Temperature (soldering, 10 sec.)Maximum Junction Temperature

45V

–0.3V ≤ V ≤ +40V

–1V

Internally Limited–65°C to +150°C

2 kV1 kV260°C150°C

Operating Ratings

Temperature RangeSupply Voltage

–40°C ≤ TJ ≤ +125°C

40V

Electrical Characteristics Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply

over full Operating Temperature Range. Unless otherwise specified, VIN = 12V, and ILOAD = 200mA.

LM2575

Symbol

Parameter

Conditions

Typ

Limit(Note 2)

Units(Limits)

SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1VOUT

Feedback Voltage

VIN = 12V , ILOAD = 0.2AVOUT = 5V

0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40VVOUT = 5V

VIN = 12V, ILOAD = 1A, VOUT = 5VVIN = 12V , ILOAD = 0.2AVOUT = 3.3V

0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40VVOUT = 3.3V

VIN = 12V, ILOAD = 1AVIN = 12V , ILOAD = 0.2AVOUT = 5V

0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40VVOUT = 5V

VIN = 12V, ILOAD = 1AVIN = 25V , ILOAD = 0.2AVOUT = 12V

0.2A ≤ ILOAD ≤ 1A, 15V ≤ VIN ≤ 40VVOUT = 12V

VIN = 25V, ILOAD = 1A

1.230

1.2171.243

1.230

1.193/1.1801.267/1.280

82

VV(min)V(max)VV(min)V(max)%

VOUT

Feedback VoltageLM2575EfficiencyOutput Voltage

ηVOUT

SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 13.3

3.2343.366

3.3

3.168/3.1353.432/3.465

75

VV(min)V(max)VV(min)V(max)%

VOUT

Output VoltageLM2575-3.3EfficiencyOutput Voltage

ηVOUT

SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 15.0

4.9005.100

5.0

4.800/4.7505.200/5.250

82

VV(min)V(max)VV(min)V(max)%

VOUT

Output VoltageLM2575-5.0EfficiencyOutput Voltage

ηVOUT

SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 112

11.76012.240

12

11.520/11.40012.480/12.600

88

VV(min)V(max)VV(min)V(max)%

VOUT

Output VoltageLM2575-12Efficiency

η

August 19993M2575

LM2575MicrelElectrical Characteristics (continued)

LM2575

Symbol

Parameter

Conditions

Typ

Limit(Note 2)

Units(Limits)

DEVICE PARAMETERS, ADJUSTABLE REGULATORIBfO

Feedback Bias Current

VOUT = 5V

50

100/500

nA

DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS

Oscillator Frequency

52

47/4258/63

Saturation VoltageMax Duty Cycle (ON)Current Limit

IOUT = 1A (Note 4)(Note 5)

Peak Current, tON ≤ 3µs (Note 4)

0.9

1.2/1.4

98

93

ICL

2.2

1.7/1.33.0/3.22

7.5

30

5

10

Standby QuiescentCurrent

Thermal Resistance

ON/OFF Pin = 5V (OFF)

T Package, Junction to Ambient (Note 7)T Package, Junction to Ambient (Note 8)T Package, Junction to Case

N Package, Junction to Ambient (Note 9)WM Package, Junction to Amb. (Note 9)

50

200

6545285100

kHzkHz (min)kHz (max)VV(max)%%(min)AA(min)A(max)mA(max)mAmA(max)mAmA(max)µAµA(max)°C/W

VSATDC

IL

Output Leakage Current

VIN = 40V, (Note 6),(Note 6)Output = 0VOutput = –1VOutput = –1V

IQISTBYθJAθJAθJCθJAθJA

Quiescent Current(Note 6)

LM25754August 1999

LM2575LM2575SymbolParameterConditionsTypLimit(Note 2)MicrelUnits(Limits)ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1VIHVILIIHIILNote 1:ON/OFF Pin LogicInput LevelON /OFF Pin LogicCurrentVOUT = 0VVOUT = 5VON /OFF Pin = 5V (OFF)ON/OFF Pin = 0V (ON)1.41.242.2/2.41.0/0.830V(min)V(max)µAµA(max)µAµA(max)0.0110Absolute Maximum Rating indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the deviceis intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the ElectricalCharacteristics.All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) . All room temperature limits are100% production tested. All limits at temperature extreme are guaranteed via testing.External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When theLM2575/LM1575 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of ElectricalCharacteristics.Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output.Feedback (pin 4) removed from output and connected to 0V.Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2\" leads in a socket, oron PC board with minimum copper area.Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4\" leads soldered to PCboard containing approximately 4 square inches of copper area surrounding the leads.Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lowerthermal resistance further.Note 2:Note 3:Note 4:Note 5:Note 6:Note 7:Note 8:Note 9:Typical Performance CharacteristicsNormalizedFeedback Voltage*NORMALIZED FEEDBACK VOLTAGE (mV)Feedback Voltagevs Duty Cycle*20FEEDBACK VOLTAGE CHANGE (mV)2520151050-5-10-15VIN = 12VILOAD = 200mANormalized to TJ = 25˚C151050-5-10-15-2002040ILOAD = 200 mAVIN = 40VVIN = 7V-20-25-75-50-2502550751001251506080100JUNCTION TEMPERATURE (˚C)DUTY CYCLE (%)* Adjustable version onlyAugust 19995M2575

LM2575MicrelTypical Performance Characteristics (continued) (Circuit of Figure 1)Supply Current2018SUPPLY CURRENT (mA)Supply Currentvs. Duty Cycle17.5SUPPLY CURRENT (mA)STANDBY QUIESCENT CURRENT (µA)StandbyQuiescent Current200VIN = 40V1614121080102030Measured atGround PinTJ = 25˚CVOUT = 5V20.015.012.510.07.55.02.5VIN from 7V to 40V020406080100ILOAD = 200 mA150VON/OFF = 5VVIN = 12V50100ILOAD to 1A40506000-75-50-250255075100125150JUNCTION TEMPERATURE (˚C)INPUT VOLTAGE (V)DUTY CYCLE (%)Current Limit3VIN = 25VSATURATION VOLTAGE (V)OUTPUT CURRENT (A)SwitchSaturation Voltage1.2100951.0-55˚C-40˚C0.825˚CEFFICIENCY (%)EfficiencyVOUT = 12V1A9085807570650.40.60.81.060051015202530INPUT VOLTAGE (V)2200 mA200 mA11AVOUT = 3V0.6125˚C150˚C0.40-75-50-250255075100125150JUNCTION TEMPERATURE (˚C)00.23540SWITCH CURRENT (A)Minimum OperatingVoltageNORMALIZED FEEDBACK VOLTAGE (mV)Line RegulationNormalized to VIN = 10VVOUT = 5VILOAD = 500mATJ = 25STANDBY QUIESCENT CURRENT (µA)Feedback Pin Current1007550250-25-50-75-100-75-50-2502550751001251505.04.54.0INPUT VOLTAGE (V)141210820-2-4-603.53.02.52.01.51.00.50-75-50-250VOUT = 1.23VILOAD = 200 mA25507510012515051015202530JUNCTION TEMPERATURE (˚C)INPUT VOLTAGE (V)JUNCTION TEMPERATURE (˚C)NormalizedOutput Voltage100OUTPUT VOLTAGE CHANGE (mV)Oscillator Frequency+8+6NORMALIZED FREQUENCY (%)Dropout Voltage2.0INPUT-OUTPUT DIFFERENTIAL (V)7550250-25-50-75VIN = 12VILOAD = 200mANormalized to TJ = 25˚CNormalized at 25˚C+4+20-2-4--6VIN = 40V1.5ILOAD = 1A∆VOUT = 5%RIND = 0.2Ω1.0ILOAD = 200 mA0.5-100-75-50-250255075100125150VIN = 12V-8-75-50-250255075100125150JUNCTION TEMPERATURE (˚C)0-75-50-250255075100125150JUNCTION TEMPERATURE (˚C)JUNCTION TEMPERATURE (˚C)LM25756August 1999

LM2575MicrelTypical Performance Characteristics (Circuit of Figure 1)Load Transient ResponseSwitching WaveformsOutputVoltageChange+100mV0–100mVA10V0B1A0C1.0AOutputCurrent0.5A0VOUT = 5V100µS/div.D1A.5A0VOUT = 5V VIN = 20VA: Output pin voltage 10V/divB: Output pin current 1A/divC: Inductor current 0.5A/divD: Output ripple voltage 20 mV/div. AC coupledHorizontal Time Base: 5µs/divTest Circuits and Layout GuidelinesFEEDBACK+VIN17V - 40VUNREGULATEDDC INPUT+100 µFCINGND3ON/OFF524LM2575OUTPUTL1330 µHD1MBR360+VOUT5.00VCOUT470µFR2R1LOADCIN — 100µF, 75V Aluminum ElectrolyticCOUT — 470µF, 15V Aluminum ElectrolyticD1 — Schottky, MBR360L1 — 330µH, 415-0926 (AIE)R1 — 1k, 0.01%R2 — 3.065k, 0.01%5-pin TO-220 socket—2936 (Loranger Mfg. Co.)4-pin TO-3 socket—8112-AG7 (Augat Inc.)FEEDBACK+VIN17V - 40VUNREGULATEDDC INPUT+100 µFCINGND3ON/OFF524LM2575-5.0OUTPUTL1330 µHD1MBR360+VOUT5.00VCOUT220µFLOADCIN — 100µF, 75V Aluminum ElectrolyticCOUT — 330µF, 15V Aluminum ElectrolyticD1 — Schottky, MBR360L1 — 330µH, 415-0926 (AIE)5-pin TO-220 socket—2936 (Loranger Mfg. Co.)4-pin TO-3 socket—8112-AG7 (Augat Inc.)Note: Pin numbers are for TO-220 PackageFigure 1.As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transientswhich can cause problems. For minimal stray inductance and ground loops, the length of the leads indicated by heavy lines should be kept asshort as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results.Block DiagramsVINFEED-BACK143.1kINTERNALREGULATORON/OFF5ON/OFFVIN1INTERNALREGULATORON/OFF5ON/OFFFIXED GAINERROR AMPFIXED GAINERROR AMPCOMPARATOR1 AMPSWITCHDRIVERFEED-BACK+1.0k4+-+-COMPARATOR1 AMPSWITCHDRIVER-+-21.23VBAND-GAPREFERENCEOUTPUT1.23VBAND-GAPREFERENCE2OUTPUT52 kHzOSCILLATORRESETTHERMALSHUTDOWNCURRENTLIMIT3GND52 kHzOSCILLATORRESETTHERMALSHUTDOWNCURRENTLIMIT3GNDNote: Pin numbers are for the TO-220 packageFixed RegulatorAugust 1999

7

Adjustable RegulatorM2575