52kHz Simple 3A Buck Regulator - Microchip …

1 August 20051M9999-082605-BLM2576 Micrel, Simple 3A buck RegulatorGeneral DescriptionThe LM2576 series of monolithic integrated circuits provideall the active functions for a step-down ( buck ) switchingregulator. Fixed versions are available with a , 5V, or 12 Vfixed output. Adjustable versions have an output voltagerange from to 37V. Both versions are capable of drivinga 3A load with excellent line and load regulators are Simple to use because they require aminimum number of external components and include internalfrequency compensation and a fixed-frequency LM2576 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 standard series of inductors available from several differentmanufacturers are ideal for use with the LM2576 series.

2 Thisfeature greatly simplifies the design of switch-mode 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 than200 A standby current. The output switch includes cycle-by-cycle current limiting and thermal shutdown for full protectionunder fault ApplicationsFeatures , 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 3A output current Wide input voltage range:4V to 40V Wide output voltage to 37V Requires only 4 external components 52kHz fixed frequency internal oscillator Low power standby mode IQ typically < 200 A 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 ) Regulator Efficient pre- Regulator for linear regulators On-card switching regulators Positive to negative converter (inverting buck -Boost)

3 Isolated Flyback Converter using minimum number ofexternal components Negative Boost ConverterR2R17V 40 VUnregulatedDC InputLM2575+CIN100 F+VIN13 Gnd5On/Off2 Output4 FeedbackL1330 H+ D11N5822 COUT330 FR2 1kVOUT = 1 +( )+5V, 1 ARegulatedOutputNote: Pin numbers are for TO-220 Package7V 40 VUnregulatedDC +CIN100 F+VIN13 Gnd5On/Off2 Output4 FeedbackL1330 H+ D11N5822 COUT330 F+5V, 1 ARegulatedOutputNote: Pin numbers are for TO-220 PackageFixed Regulator in Typical ApplicationAdjustable Regulator in Fixed Output ApplicationMicrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 2005LM2576 Micrel, Number TemperatureStandardRoHS Compliant**RangePackageLM2576BT* LM2576WT* 40 C to +85 40 C to +85 40 C to +85 CTO-220-5LM2576-12BT LM2576-12WT 40 C to +85 CTO-220-5LM2576BU*LM2576WU* 40 C to +85 40 C to +85 40 C to +85 CTO-263-5LM2576-12 BULM2576-12WU 40 C to +85 CTO-263-5* Adjustable output regulators .

4 **RoHS compliant with "hot-melting solder" exemption. Contact factory for bent or staggered leads ConfigurationsGND5- ON/OFF4- FEEDBACK3- GROUND2- OUTPUT1- VIN5-LEAD TO-263 (U)GND5- ON/OFF4- FEEDBACK3- GROUND2- OUTPUT1- VIN5-LEAD TO-220 (T)Ordering InformationAugust 20053M9999-082605-BLM2576 Micrel, Characteristics Specifications with standard typeface are for TJ = 25 C, and those with boldface type applyover full Operating Temperature Range. Unless otherwise specified, VIN = 12V, and ILOAD = (Note 2)(Limits)SYSTEM PARAMETERS, ADJUSTABLE regulators (Note 3) Test Circuit Figure 1 VOUTF eedback VoltageVIN = 12V , ILOAD = = (min) (max)VOUTF eedback ILOAD 3A, 8V VIN = (min) (max) EfficiencyVIN = 12V, ILOAD = 3A, VOUT = 5V82%SYSTEM PARAMETERS, regulators (Note 3) Test Circuit Figure 1 VOUTO utput VoltageVIN = 12V , ILOAD = = (min) (max)VOUTO utput ILOAD 3A, 6V VIN = (min) (max) EfficiencyVIN = 12V, ILOAD = 3A75%SYSTEM PARAMETERS, 5V regulators (Note 3) Test Circuit Figure 1 VOUTO utput VoltageVIN = 12V , ILOAD = = (min) (max)VOUTO utput ILOAD 3A, 8V VIN = (min) (max) EfficiencyVIN = 12V, ILOAD = 3A82%SYSTEM PARAMETERS, 12V regulators (Note 3)

5 Test Circuit Figure 1 VOUTO utput VoltageVIN = 25V , ILOAD = = (min) (max)VOUTO utput ILOAD 3A, 15V VIN 40V12 VLMLM2576-12 VOUT = (min) (max) EfficiencyVIN = 25V, ILOAD = 3A88%Operating RatingsTemperature Range 40 C TJ +125 CSupply Voltage40V Absolute Maximum Ratings (Note 1)Maximum Supply Voltage45 VON/OFF Pin Input Voltage V +40 VOutput Voltage to Ground (Steady State) 1 VPower DissipationInternally LimitedStorage Temperature Range 65 C to +150 CMinimum ESD RatingC = 100pF, R = 2 kVFB Pin1 kVLead Temperature (soldering, 10 sec.)260 CMaximum Junction Temperature150 CM9999-082605-B4 August 2005LM2576 Micrel, Characteristics (continued)LM2576 UnitsSymbolParameterConditionsTypLimit(L imits)(Note 2)DEVICE PARAMETERS, ADJUSTABLE REGULATORIBF eedback Bias CurrentVOUT = 5V50100/500nADEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORSfOOscillator Frequency52kHz47/42kHz (min)58/63kHz (max)VSATS aturation VoltageIOUT = 3A (Note 4) (max)DCMax Duty Cycle (ON)(Note 5)98%93%(min)ICLC urrent LimitPeak Current, tON 3 s (Note 4) (min) (max)ILOutput Leakage Current VIN = 40V, (Note 6),Output = 0V2mA(max)Output = (Note 6)Output = 1V30mA(max)IQQuiescent Current(Note 6)5mA10mA(max)ISTBYS tandby QuiescentON/OFF Pin = 5V (OFF)50 ACurrent200 A(max)

6 JAThermal ResistanceT,U Package, Junction to Ambient (Note 7)65 C/W JAT,U Package, Junction to Ambient (Note 8)45 JCT,U Package, Junction to Case2 August 20055M9999-082605-BLM2576 Micrel, Characteristics (continued)LM2576 UnitsSymbolParameterConditionsTypLimit(L imits)(Note 2)ON/OFF CONTROL, FIXED and ADJUSTABLE regulators Test Circuit Figure 1 VIHON/OFF Pin LogicVOUT = (min)VILI nput LevelVOUT = (max)IIHON /OFF Pin LogicON /OFF Pin = 5V (OFF)4 ACurrent30 A(max)IILON/OFF Pin = 0V (ON) A10 A(max)Note 1:Absolute 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 2:All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face).

7 All room temperature limits are100% production tested. All limits at temperature extreme are guaranteed via 3:External components such as the catch diode, inductor, input and output capacitors can affect switching Regulator system performance. When theLM2576/LM1576 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of 4:Output (pin 2) sourcing current. No diode, inductor or capacitor connected to 5:Feedback (pin 4) removed from output and connected to 6:Feedback (pin 4) removed from output and connected to 12V to force the output transistor 7: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 8: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 9:Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads.

8 Additional copper will lowerthermal resistance Performance CharacteristicsNormalizedFeedback Voltage*JUNCTION TEMPERATURE ( C)NORMALIZED FEEDBACK VOLTAGE (mV)2520151050-5-10-15-20-25-75 -50 -25 0 25 50 75 100 125 150 VIN = 12 VILOAD = 200mANormalized to TJ = 25 CFeedback Voltagevs Duty Cycle*DUTY CYCLE (%)FEEDBACK VOLTAGE CHANGE (mV)20151050-5-10-15-20 ILOAD = 200 mAVIN = 40 VVIN = 7V020406080100* Adjustable version onlyM9999-082605-B6 August 2005LM2576 Micrel, Performance Characteristics (continued) (Circuit of Figure 1)Supply CurrentINPUT VOLTAGE (V)SUPPLY CURRENT (mA)20 Measured atGround PinTJ = 25 CVOUT = 5V18161412108640 102030405060 ILOAD to 1 ASupply Currentvs. Duty CycleDUTY CYCLE (%) from 7V to 40 VILOAD = 200 mASUPPLY CURRENT (mA)JUNCTION TEMPERATURE ( C)200150100500-75 VIN = 12 VSTANDBY QUIESCENT CURRENT ( A)StandbyQuiescent CurrentVIN = 40V-50 -25 0 25 50 75 100 125 150 Current LimitJUNCTION TEMPERATURE ( C)3210-75 VIN = 25 VOUTPUT CURRENT (A)INPUT VOLTAGE (V)100 EFFICIENCY (%)EfficiencyVOUT = 12V-50 -25 0 25 50 75 100 125 1509590858075706560200 mA200 mAVOUT = 3V1A0510 15 20 25 30 35 40 Minimum OperatingVoltageJUNCTION TEMPERATURE ( C) = 200 mAINPUT VOLTAGE (V)Line RegulationINPUT VOLTAGE (V)140 NORMALIZED FEEDBACK VOLTAGE (mV)JUNCTION TEMPERATURE ( C)100-100-75 STANDBY QUIESCENT CURRENT ( A)

9 Feedback Pin Current-50 -25 0 25 50 75 100 125 150 VOUT = -50 -25 025 50 75 100 125 150121086420-2-4-65 10152025307550250-25-50-75 JUNCTION TEMPERATURE ( C)+8-8-75 NORMALIZED FREQUENCY (%)Oscillator Frequency-50 -25 0 25 50 75 100 125 150+6+4+20-2-4--6 VIN = 12 VVIN = 40 VNormalized at 25 CNormalized to VIN = 10 VVOUT = 5 VILOAD = 500mATJ = 25 VON/OFF = 5 VSwitchSaturation VoltageSWITCH CURRENT (A) VOLTAGE (V) C125 C150 C-40 CDropout VoltageJUNCTION TEMPERATURE ( C)INPUT-OUTPUT DIFFERENTIAL (V) -50 -25 0 25 50 75 100 125 150 VOUT = 5%RIND = ILOAD = 1 AILOAD = 200 VoltageJUNCTION TEMPERATURE ( C)OUTPUT VOLTAGE CHANGE (mV)1007550250-25-50-75-100-75 -50 -25 0 25 50 75 100 125 150 VIN = 12 VILOAD = 200mANormalized to TJ = 25 C1 AAugust 20057M9999-082605-BLM2576 Micrel, Transient Response+100mV0-100mVOutputVoltageChange 3A2A1A0 OutputCurrent50V04A2A04A2A0 ABCD5 WaveformsA: Output pin voltage 50V/divB: Output pin current 2A/divC: Inductor current 2A/divD: Output ripple voltage 50 mV/div.

10 , AC coupledHorizontal Time Base: 5 S/divVOUT = 5V VIN = 45 VTypical Performance Characteristics (Circuit of Figure 1)M9999-082605-B8 August 2005LM2576 Micrel, +100 F+VIN13 GND5ON/OFF2 OUTPUT4 FEEDBACKL1330 H+D1 MBR360 COUT470 - 40 VUNREGULATEDDC INPUTCINLOADCIN 100 F, 75V Aluminum ElectrolyticCOUT 470 F, 15V Aluminum ElectrolyticD1 Schottky, MBR360L1 330 H, 415-0926 (AIE)R1 1k, , TO-220 socket 2936 (Loranger Mfg. Co.)4-pin TO-3 socket 8112-AG7 (Augat Inc.) +100 F+VIN13 GND5ON/OFF2 OUTPUT4 FEEDBACKL1330 H+D111DQ06 COUT220 : Pin numbers are for TO-220 Package7V - 40 VUNREGULATEDDC INPUTCINCIN 100 F, 75V Aluminum ElectrolyticCOUT 330 F, 15V Aluminum ElectrolyticD1 Schottky, 11DQ06L1 100 H, 415-0926 (AIE)5-pin TO-220 socket 2936 (Loranger Mfg.)