LM2576 3-Ampere Step-Down Voltage Regulator

LM2576 is a switch-mode step down ( Buck Converter ) voltage regulator that can provide a fix output voltage. Its output voltage can also be adjusted in a range of 1.23V to 37V by connecting external components. This IC is very simple to use, and this feature makes it ideal for a wide range of applications. It has built-in fault protection against over currents, voltages and temperature.

LM2576 Pinout Diagram

This picture depicts a pinout diagram of an LM2576 buck voltage regulator. It works either in fix voltage or in adjustable voltage mode.  For details of each pin, refer to the next section.

LM2576 Pinout diagram Buck Voltage Regulator

Pin Configuration Description

It is important to know the description of pins of IC before using it. The functions of all the pins of LM2576 are explained below:

Pin#01: VIN

It is the input pin where a signal to be regulated is applied.

Pin#02: Output

This pin is used to obtain the regulated signal output.

Pin#03: Ground

The ground pin is connected to the ground of the circuit.

Pin#04: Feedback

The feedback is an input pin used to set output voltage in case of adjustable output. To adjust the output voltage, it is connected to the midpoint of the feedback divider network. In case of fixed output, connect this pin to the capacitor.

Pin#05: ~ON /OFF

It is the enable input pin. This pin should not be left unconnected. Connect it to the ground to enable the voltage regulator. To disable the regulator, connect this pin to HIGH logic.

LM2576 Features

  • It is a fixed frequency voltage regulator having an internal oscillator of frequency 52kHz
  • Input voltage can be applied up to 40V and up to 60V for HV versions.
  • This regulator can provide fixed output voltages of 3.3, 5, 12 and 15 volts.
  • The output voltage can be varied from 1.23V to 37V by connecting external components.
  • It can withstand a tolerance of ±4% on output voltage when the input voltage is in the range specified and output load conditions are satisfied, and tolerance of ±10% on the oscillator frequency.
  • Its output current is specified up to 3A.
  • Protection circuitry includes thermal shutdown and current limit protection.
  • It has an Undervoltage lockout circuit which keeps the input voltage in a range and keeps the regulator off until it comes to a certain threshold level.

LM2576 Equivalent and Alternative Options

LM1117, CS51411, LM723, LM7912

Where to use 3A Step-Down Voltage Regulator?

LM2576  is a 3A voltage regulator which provides an excellent line and load regulation. It is suitable for driving 3A loads. Due to its convenient use, it is also used as a step-down switching regulator.

It can use readily available inductors. This feature makes it ideal for designing switch-mode power supplies as it greatly simplifies their design. So. If you are looking for a linear buck voltage regulator that can drive 3A loads and provide an output in the range of 1.23V to 37V with an efficiency of 88% then you can use this IC.

How to use LM2576?

The use of this chip is explained through the circuit given below. In this section, we will see examples of how to use LM2576 in fix voltage and adjustable voltage mode.

Fix Voltage Regulator Example Circuit

This circuit is for a fixed voltage regulator which takes an unregulated DC voltage at its pin 1 and then converts it into a +5V regulated voltage which is obtained from pin 2. An input capacitor is required for stability.  The output capacitor acts as a filter and removes ripples from the output voltage. It also provides loop stability.

LM2576 Fixed 5 volt power supply circuit example

A Schottky diode 1N5822 connects across an output pin and L1 inductor. When regulator internal switch is off, it offers a path for inductor current. For normal operation, you should connect ~ON/OFF pin to the ground terminal.

Before selecting a Schottky diode, you should make sure that the rating of this diode is 1.2 times greater than the load current requirement or output current.

Adjustable Voltage Power supply Circuit Example

LM2576 adjustable voltage power supply circuit example

To adjust the output voltage, two resistors R1 and R2 are connected which constitute a feedback network. The output voltage or the values of resistors can be calculated by keeping two values constant and put them in the following equation to find third value:

VOUT= VREF(1 + R2/R1)
Where   VREF=1.23V.

Applications

The LM2576 is a high-efficiency Buck regulator which is used in a large variety of applications which include:

  • Designing of Switch-mode power supplies
  • It is an efficient pre-regulator for designing Linear Regulators
  • These are On-Card Switching Regulators
  • It can also be used to convert a positive input voltage to negate output voltage.

2D Diagram

2D Diagram

Datasheet

LM2576 Datasheet

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