General Description                                                                    Typical Performance Characteristics

                                                                                                        (Circuit of Figure 2)

The LM2576 series of regulators are monolithic integrated                              

circuits that provide all the active functions for a step-down

(buck) switching regulator, capable of driving 3A load with               

excellent line and load regulation. These devices are avail-

able 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 LM2576 series offers a high-efficiency replacement for

popular three-terminal linear regulators. It substantially re-

duces the size of the heat sink, and in some cases no heat

sink is required.

A standard series of inductors optimized for use with the

LM2576 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 out-

put voltage within specified input voltages and output load

conditions, and ±10% on the oscillator frequency. External

shutdown is included, featuring 50 µA (typical) standby cur-

rent. The output switch includes cycle-by-cycle current limit-

ing, 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 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

Applications

♦ Simple high-efficiency step-down (buck) regulator

♦ Efficient pre-regulator for linear regulators

♦ On-card switching regulators

♦ Positive to negative converter (Buck-Boost)