LM2576T Regulator: Circuit, Pinout, and Datasheet

The LM2576T series of regulators are monolithic integrated circuits that make designing a stepdown switching regulator simple and straightforward (buck converter). All circuits in this series have excellent line and load regulation and can drive a 3.0 A load.

Fixed output voltages of 3.3 V, 5.0 V, 12 V, and 15 V, as well as an adjustable output version, are available for these devices.

These regulators were created with the goal of reducing the number of external components in the power supply and making it easier to build. Several inductor manufacturers offer standard series of inductors that are optimized for use with the LM2576T. Because the LM2576T converter is a switchmode power supply, it has a far higher efficiency than traditional three-terminal linear regulators, especially at higher input voltages.

In many circumstances, the amount of power dissipated is so minimal that a heatsink is not necessary, or its size can be drastically decreased. Several manufacturers offer a standard set of inductors that are optimized for use with the LM2576T. The design of the switchmode power supply is substantially simplified as a result of this characteristic.

The LM2576T has a guaranteed ±4% output voltage tolerance within defined input voltages and output load circumstances, as well as a ±10% oscillator frequency tolerance (±2% over 0°C to 125°C). External shutdown is included, with a standby current of 80 A (typical). The output switch has cycle-by-cycle current limiting and thermal shutdown for complete protection in the event of a fault.

Pinout

Footprint

3D Model

• Versions with 3.3 V, 5.0 V, 12 V, 15 V, and Variable Output

• Output Voltage Range: 1.23 to 37 V ±4% Maximum Over Line and Load Conditions

• 3.0 A Output Current is Guaranteed

• Wide Input Voltage Range

• Only 4 External Components are Required

• 52 kHz Fixed Frequency Internal Oscillator

• TTL Shutdown Capability, Low Power Standby Mode

• High Efficiency

• Uses Commonly Available Standard Inductors

• Thermal Shutdown and Current Limit Protection

• Moisture Sensitivity Level (MSL) Equals 1

• Pb−Free Packages are Available

Functional Block Diagram

Typical Application

Fixed Output Voltage Versions

Cin − 100 μF, 75 V, Aluminium Electrolytic

Cout − 1000 μF, 25 V, Aluminium Electrolytic

D1 − Schottky, MBR360

L1 − 100 μH, Pulse Eng. PE−92108

R1 − 2.0 k, 0.1%

R2 − 6.12 k, 0.1%

Adjustable Output Voltage Versions

Vout=Vref*( 1.0+R2/R1)

R2=R1*(Vout/Vref-1.0)

Where Vref = 1.23 V, R1

between 1.0 k and 5.0 k

The layout of the printed circuit board is critical in any switching regulator. Voltage transients caused by rapidly switching currents caused by wiring inductance, stray capacitance, and parasitic inductance of printed circuit board traces can cause electromagnetic interference (EMI) and disrupt the desired operation. To minimize inductance and ground loops, the length of the leads indicated by thick lines should be kept as short as possible, as shown in the typical test circuit above.

Single point grounding (as stated) or ground plane construction should be used for the greatest results.

In order to avoid coupling to sensitive electronics, the PCB area linked to the LM2576's Pin 2 (emitter of the internal switch) should be reduced to a minimum.

The feedback is another delicate component of the circuit. It's critical to keep the sensitive feedback wiring as short as possible. When utilizing the adjustable version of the LM2576 regulator, physically put the programming resistors near the regulator to ensure this.

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Package

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