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National Semiconductor LM257x SIMPLE SWITCHER® Step-Down Voltage RegulatorsNational Semiconductor LM257x SIMPLE SWITCHER® Step-Down Voltage Regulators are high efficiency devices ranging from 0.5A to 3A output current. National Semiconductor LM2574 and LM2574HV SIMPLE SWITCHER Step-Down Voltage Regulators provide all the active functions for a step-down (buck) switching regulator capable of driving a 0.5A load with excellent line and load regulation. LM2575 and LM2575HV Step-Down Voltage Regulators provide all the active functions for a step-down (buck) switching regulator capable of driving a 1A load with excellent line and load regulation. LM2576 and LM2576HV Step-Down Voltage Regulators provide all the active functions for a step-down (buck) switching regulator capable of driving 3A load with excellent line and load regulation. LM2577 SIMPLE SWITCHER 3A Step-Up Voltage Regulators provide all the power and control functions for step-up (boost), flyback, and forward converter switching regulators. National Semiconductor LM257x devices are a high-efficiency replacement for popular three-terminal linear regulators.
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LM2574 Features
- 3.3V, 5V, 12V, 15V, and adjustable output versions
- Adjustable version output voltage range, 1.23V to 37V (57V for HV version) ±4% max over line and load conditions
- Guaranteed 0.5A output current
- Wide input voltage range, 40V, up to 60V for HV version
- Requires only 4 external components
- 52kHz fixed frequency internal oscillator
- TTL shutdown capability, low power standby mode
- High efficiency
- Uses readily available standard inductors
- Thermal shutdown and current limit protection
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LM2574 Applications
- Simple high-efficiency step-down (buck) regulator
- Efficient pre-regulator for linear regulators
- On-card switching regulators
- Positive to negative converter (Buck-Boost)
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Application Circuit
LM2575 Features
- 3.3V, 5V, 12V, 15V, and adjustable output versions
- Adjustable version output voltage range, 1.23V to 37V (57V for HV version) ±4% max over line and load conditions
- Guaranteed 1A output current
- Wide input voltage range, 40V up to 60V for HV version
- Requires only 4 external components
- 52 kHz fixed frequency internal oscillator
- TTL shutdown capability, low power standby mode
- High efficiency
- Uses readily available standard inductors
- Thermal shutdown and current limit protection
- P+ Product Enhancement tested
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LM2575 Applications
- Simple high-efficiency step-down (buck) regulator
- Efficient pre-regulator for linear regulators
- On-card switching regulators
- Positive to negative converter (Buck-Boost)
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Application Circuit
LM2576 Features
- 3.3V, 5V, 12V, 15V, and adjustable output versions
- Adjustable version output voltage range, 1.23V to 37V (57V for HV version) ±4% max over line and load conditions
- Guaranteed 3A output current
- Wide input voltage range, 40V up to 60V for HV version
- Requires only 4 external components
- 52 kHz fixed frequency internal oscillator
- TTL shutdown capability, low power standby mode
- High efficiency
- Uses readily available standard inductors
- Thermal shutdown and current limit protection
- P+ Product Enhancement tested
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LM2576 Applications
- Simple high-efficiency step-down (buck) regulator
- Efficient pre-regulator for linear regulators
- On-card switching regulators
- Positive to negative converter (Buck-Boost)
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Application Circuit
LM2577 Features
- Requires few external components
- NPN output switches 3.0A, can stand off 65V
- Wide input voltage range: 3.5V to 40V
- Current-mode operation for improved transient response, line regulation, and current limit
- 52kHz internal oscillator
- Soft-start function reduces in-rush current during start-up
- Output switch protected by current limit, under-voltage lockout, and thermal shutdown
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LM2577 Applications
- Simple boost regulator
- Flyback and forward regulators
- Multiple-output regulator
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Application Circuit
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