Texas Instruments LM2576T-3.3/LB03

Overview

LM2576T-3.3/LB03 from Texas Instruments is a monolithic 3-A non-synchronous step-down DC-DC converter in TO-220-5 (KC) package, delivering fixed 3.3-V output with ±4% regulation over line and load, 40-V max input voltage, and 52-kHz fixed-frequency operation. It serves as a high-efficiency replacement for linear regulators in embedded power rails, reducing heat sink requirements and enabling compact 3.3-V supply generation with only four external components.

For engineers reviewing the LM2576T-3.3/LB03 datasheet, LM2576T-3.3/LB03 pinout, LM2576T-3.3/LB03 application, or LM2576T-3.3/LB03 equivalent, key selection considerations include its 3-A continuous output capability, TTL-compatible ON/OFF control with 50-μA standby current, cycle-by-cycle current limiting, thermal shutdown protection, and compatibility with standard off-the-shelf inductors.

Technical Context

The LM2576T-3.3/LB03 implements a fixed-frequency buck topology using an internal NPN transistor switch, error amplifier, bandgap reference, and 52-kHz oscillator. Its feedback loop senses output voltage directly at the FB pin (shorted to VOUT for fixed versions), enabling stable regulation without external resistive dividers.

It operates in active mode when the ON/OFF pin voltage falls below 1.2 V, entering shutdown with 50-μA quiescent current when pulled above 1.4 V. Protection includes cycle-by-cycle current limiting (ICL = 4.2–6.9 A), thermal shutdown, and automatic frequency foldback to ~11 kHz during overload or short-circuit conditions.

Key Specifications

Pinout & Package

LM2576T-3.3/LB03 uses the KC (TO-220-5) package with 10.16 mm × 8.51 mm body size and thermally enhanced metal tab connected to GND. The tab must be mounted to a heatsink or large copper pour for thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LM2576T-3.3/KG03, LM2576T-3.3/LB03 offers identical regulation and thermal performance but with distinct TI internal marking; versus LM2576HVT-3.3/LB03, it trades 20-V input headroom for lower cost and proven reliability in ≤40-V industrial applications.

Availability

LM2576T-3.3/LB03 is available at Aetrix Electronics and suitable for industrial motor drives, network equipment PSUs, home appliance control boards, and test & measurement instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for LM2576T-3.3/LB03 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in high-reliability power conversion ICs.

The LM2576 series was designed as a rugged, easy-to-use SIMPLE SWITCHER® solution for replacing linear regulators in cost-sensitive, thermally constrained industrial and consumer power supplies.

FAQ

What is the maximum input voltage rating for LM2576T-3.3/LB03?

The LM2576T-3.3/LB03 has a maximum input voltage rating of 40 V, with absolute maximum stress limit at 45 V. Operation beyond 40 V risks permanent damage and violates recommended operating conditions. For 48-V or higher input systems, the LM2576HVT-3.3/LB03 (60-V rated) is the appropriate alternative. Always verify input transient margins against this 40-V limit in your design.

Does LM2576T-3.3/LB03 require an external feedback resistor divider?

No, LM2576T-3.3/LB03 does not require an external feedback resistor divider. As a fixed-output variant, its internal feedback network is factory-trimmed to 3.3 V, and the FEEDBACK pin (Pin 4) is internally connected to the output. External connection of this pin invalidates regulation and must be avoided. Only adjustable versions (e.g., LM2576ADJ) require external resistors.

How is thermal management handled on LM2576T-3.3/LB03?

LM2576T-3.3/LB03 uses the metal tab (Pin 3 GROUND and TAB) as its primary thermal path. In the KC (TO-220-5) package, the tab must be soldered to a large copper area or external heatsink. With proper mounting, junction-to-ambient thermal resistance is 32.4°C/W. Without heatsinking, power dissipation is limited to ~1.5 W at 25°C ambient - insufficient for 3-A loads at high VIN–VOUT differentials.

Can LM2576T-3.3/LB03 be synchronized to an external clock?

No, LM2576T-3.3/LB03 cannot be synchronized to an external clock. It features a fixed internal 52-kHz oscillator with no synchronization pin or frequency adjustment capability. For designs requiring clock synchronization or variable frequency, consider newer alternatives like the LMR51430 or LM76003, which support external sync and programmable switching frequencies.

What protection features are integrated into LM2576T-3.3/LB03?

LM2576T-3.3/LB03 integrates cycle-by-cycle current limiting (4.2–6.9 A), thermal shutdown (150°C), and undervoltage lockout (internal). It also features automatic frequency foldback to ~11 kHz during overload or short-circuit events to reduce average power dissipation. These protections operate without external components, ensuring robust fault handling in industrial environments.