LM2574/LM2574HV

SIMPLE SWITCHER™ 0.5A Step-Down Voltage Regulator

General Description

The LM2574 series of regulators are monolithic integrated circuits that 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. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V, and an adjustable output version.

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed-frequency oscillator.

The LM2574 series offers a high-efficiency replacement for popular three-terminal linear regulators. Because of its high efficiency, the copper traces on the printed circuit board are normally the only heat sinking needed.

A standard series of inductors optimized for use with the LM2574 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies.

Other features include a guaranteed ±4% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 50 µA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions.

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
• 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

Applications

• Simple high-efficiency step-down (buck) regulator
• Efficient pre-regulator for linear regulators
• On-card switching regulators
• Positive to negative converter (Buck-Boost)

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Maximum Supply Voltage

LM2574 45V

LM2574HV 63V

ON /OFF Pin Input Voltage −0.3V ≤ V ≤ +V_IN

Output Voltage to Ground (Steady State) −1V

Minimum ESD Rating (C = 100 pF, R = 1.5 kΩ) 2 kV

Storage Temperature Range −65˚C to +150˚C

Lead Temperature (Soldering, 10 seconds) 260˚C

Maximum Junction Temperature 150˚C

Power Dissipation Internally Limited

Operating Ratings

Temperature Range

LM2574/LM2574HV −40˚C ≤ T_J ≤ +125˚C

Supply Voltage

LM2574 40V

LM2574HV 60V

Typical Application (Fixed Output Voltage Versions)

Note: Pin numbers are for 8-pin DIP package.

Connection Diagrams

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