Microchip Technology LM2575-3.3BT

Overview

LM2575-3.3BT from Texas Instruments is a monolithic step-down (buck) switching regulator IC delivering fixed 3.3 V output at up to 1 A load current, with internal 41 kHz oscillator, thermal shutdown, and current-limit protection. It replaces linear regulators in power supplies for microcontrollers, embedded logic, and industrial control modules where efficiency and thermal management are critical.

For engineers reviewing the LM2575-3.3BT datasheet, LM2575-3.3BT pinout, LM2575-3.3BT application, or LM2575-3.3BT equivalent, key selection factors include its fixed-output architecture, TO-220 package thermal performance, dropout behavior under transient load, and compatibility with standard buck external components (diode, inductor, capacitors).

Technical Context

The LM2575-3.3BT integrates a PWM controller, power switch, and protection circuitry in a single silicon die. Its 41 kHz fixed-frequency operation enables predictable EMI filtering and simplifies inductor selection using standard off-the-shelf 100–330 µH shielded chokes.

It operates over input voltages from 4.75 V to 40 V and maintains ±4% output voltage regulation across line, load, and temperature variations. Internal current limiting and thermal shutdown prevent damage during overload or ambient temperature excursions beyond 125°C junction limit.

Key Specifications

Pinout & Package

LM2575-3.3BT is housed in a 5-pin TO-220 package with exposed metal tab (pin 2) for thermal conduction to heatsink. Pin 1 is Input, Pin 2 is Ground/Tab, Pin 3 is Output, Pin 4 is Feedback (internally tied to 3.3 V reference), Pin 5 is ON/OFF (active-low enable).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck regulator applications.

Compared with LM2575T-3.3, the LM2575-3.3BT shares identical performance but differs in environmental compliance labeling; versus LM2576-3.3, it trades peak current headroom for smaller magnetics and lower system cost in sub-1 A designs.

Availability

LM2575-3.3BT is available at Aetrix Electronics and suitable for industrial control systems, automotive body electronics, and medical instrumentation requiring stable component supply and long-term manufacturability.

Supply support for LM2575-3.3BT 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 company specializing in analog, embedded processing, and power management technologies with over 50 years of power conversion leadership.

The LM2575 series was designed as a cost-optimized, easy-to-use buck regulator family for replacing linear regulators in mid-power industrial and automotive applications where simplicity and reliability are prioritized over ultra-high efficiency or ultra-low IQ.

FAQ

What is the maximum input voltage rating for the LM2575-3.3BT?

The LM2575-3.3BT supports an absolute maximum input voltage of 45 V, with recommended continuous operation from 4.75 V to 40 V. Exceeding 40 V may reduce reliability and lifetime, especially at elevated temperatures. The device's internal protection does not guarantee safe operation beyond 45 V, so input transient clamping (e.g., TVS diode) is advised in 24 V industrial environments where load dump can reach 40–60 V peaks. Always verify derating curves in the LM2575-3.3BT datasheet for your specific thermal conditions.

Does the LM2575-3.3BT require an external feedback resistor network?

No, the LM2575-3.3BT does not require external feedback resistors because it is a fixed-output variant with the 3.3 V reference internally connected to the FB pin. Pin 4 (FB) must remain unconnected or floating for proper operation. Adding external resistors will disrupt regulation and cause output voltage error. This fixed architecture simplifies layout, reduces component count, and improves long-term stability compared to adjustable versions like the LM2575-ADJ. Always confirm pin 4 is unconnected in your LM2575-3.3BT schematic.

Can the LM2575-3.3BT be used in battery-powered applications with deep discharge?

Yes, the LM2575-3.3BT operates down to 4.75 V input, making it suitable for 2-cell Li-ion (6–8.4 V) or 4-cell NiMH (4.8–6 V) battery systems. However, its minimum input requirement means it cannot regulate from a single Li-ion cell (<4.2 V) or deeply discharged multi-cell pack. For such cases, consider a low-V_IN buck like the TPS54302. The LM2575-3.3BT's 41 kHz switching frequency also helps maintain efficiency across the battery discharge curve, unlike higher-frequency converters that suffer increased gate charge losses at low V_IN.

How is thermal performance affected by PCB layout for the LM2575-3.3BT?

Thermal performance of the LM2575-3.3BT depends critically on PCB copper area connected to Pin 2 (GND/Tab). TI recommends ≥4 cm² of 2-oz copper directly under the tab, thermally vias (≥6× 12-mil) to inner/ground planes, and optional external heatsink. Without adequate copper, junction temperature can exceed 125°C at 1 A and 50°C ambient, triggering thermal shutdown. The LM2575-3.3BT's TO-220 tab is electrically GND - isolation from chassis ground is required if safety isolation is needed. Always validate thermal rise with IR imaging in your final LM2575-3.3BT layout.

Is the LM2575-3.3BT pin-compatible with the LM2575-5.0BT?

No, the LM2575-3.3BT and LM2575-5.0BT share identical TO-220-5 pinout, package dimensions, and terminal functions - they are mechanically and electrically pin-compatible. Both use Pin 1 (IN), Pin 2 (GND/Tab), Pin 3 (OUT), Pin 4 (FB), and Pin 5 (ON/OFF) with identical roles. The only difference is the internal feedback setting, resulting in fixed 3.3 V vs. 5.0 V output. This allows direct substitution in existing layouts when changing output voltage requirements, provided downstream components tolerate the new rail voltage.