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LM2576
Series SIMPLE SWITCHER(RM) 3A Step-Down Voltage Regulator
TL/H/11476
LM2576/LM2576HV
Series
SIMPLE
SWITCHER
Step-Down
Voltage
Regulator
September 1996
LM2576/LM2576HV Series
SIMPLE SWITCHERÉ 3A Step-Down Voltage Regulator
General Description
The LM2576 seriesof regulatorsare monolithic integrated
circuitsthat provideallthe active functionsfora step-down
(buck) switching regulator, capableof driving3A load with
excellentlineand load regulation. These devicesare avail-
ablein fixed output voltagesof 3.3V,5V, 12V, 15V,andan
adjustable output version.
Requiringa minimum numberof external components,
these regulatorsare simpletouseand include internalfre-
quency compensationanda fixed-frequency oscillator.
The LM2576 series offersa high-efficiency replacementfor
popular three-terminal linear regulators.It substantiallyre-
ducesthesizeofthe heat sink,andin some casesno heat
sinkis required. standard seriesof inductors optimizedfor use withthe
LM2576are available from several different manufacturers.
This feature greatly simplifiesthe designof switch-mode
power supplies.
Otherfeatures includea guaranteed g4% tolerance onout-
put voltage within specified input voltagesand output load
conditions,and g10%onthe oscillator frequency. External
shutdownis included, featuring50mA (typical) standbycur-
rent.The output switch includes cycle-by-cycle current limit-
ing,as wellas thermal shutdownforfull protection under
fault conditions.
Features 3.3V,5V, 12V, 15V, and adjustable output versions Adjustable version output voltage range,
1.23Vto37V (57VforHV version) g4% max over
lineand load conditions Guaranteed3A output current Wide input voltage range, 40Vupto60Vfor version Requires only4 external components52 kHz fixed frequency internal oscillator TTL shutdown capability,low power standby mode High efficiency Uses readily available standard inductors Thermal shutdownand current limit protection Pa Product Enhancement tested
Applications Simple high-efficiency step-down (buck) regulator Efficient pre-regulatorfor linear regulators On-card switching regulators Positiveto negative converter (Buck-Boost)
Typical Application (Fixed Output Voltage Versions)
TL/H/11476–1
FIGURE1
Block Diagram
3.3VR2e1.7k
5V,R2e3.1k
12V,R2e 8.84k
15V,R2e 11.3k
TL/H/11476–2ForADJ. Versione Open,R2e0X
Patent Pending
SIMPLE SWITCHERÉ isaregistered trademarkof NationalSemiconductor Corporation.
C1996National SemiconductorCorporation RRD-B30M106/Printed inU.S.A. http://
