Microchip Technology LM2575WT

Overview

LM2575WT from Micrel is an adjustable-output monolithic buck switching regulator in TO-220 package, delivering up to 1A output current with 52kHz fixed-frequency operation, ±2% feedback voltage tolerance, and integrated thermal shutdown and cycle-by-cycle current limiting. It replaces linear regulators in industrial power supplies requiring 4V–40V input and 1.23V–37V output.

For engineers reviewing the LM2575WT datasheet, LM2575WT pinout, LM2575WT application, or LM2575WT equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative options, and supply support for production-grade embedded power designs.

Technical Context

The LM2575WT implements a fixed-frequency PWM control architecture with internal 1.23V bandgap reference, error amplifier, and 52kHz oscillator. Its output switch features 1.2V max saturation voltage at 1A, enabling efficient step-down conversion without external gate drivers.

Thermal shutdown activates at 150°C junction temperature, and current limit is guaranteed at 1.7A min peak. Standby quiescent current is ≤200µA when ON/OFF pin is high, supporting low-power system sleep modes while maintaining fast wake-up response.

Key Specifications

Pinout & Package

LM2575WT uses a 5-pin TO-220 package with integral heat sink tab (pin 3). The tab is electrically connected to GND and must be mounted to a thermally conductive plane or heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2575WT, LM2575T-5.0 offers plug-and-play 5V regulation but sacrifices adjustability, while LM2596T-ADJ delivers higher performance at the cost of compatibility - neither is pin-compatible, so PCB changes are required for either alternative.

Availability

LM2575WT is available at Aetrix Electronics and suitable for industrial power supplies, automotive subsystems, and medical instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging with high-melting solder exemption.

Supply support for LM2575WT 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

Micrel Inc. was a U.S.-based semiconductor company specializing in power management, analog, and timing solutions before its acquisition by Microchip Technology in 2015.

The LM2575 product line was designed as a drop-in replacement for linear regulators in medium-power DC-DC conversion, targeting cost-sensitive industrial and embedded applications where simplicity, reliability, and thermal robustness were prioritized over ultra-high efficiency or miniaturization.

FAQ

What is the maximum input voltage rating for LM2575WT?

The absolute maximum input voltage for LM2575WT is 45V, but the recommended operating range is 4V to 40V DC. Exceeding 40V continuously risks exceeding internal power dissipation limits and triggering thermal shutdown, especially at high duty cycles or elevated ambient temperatures. Always include transient voltage suppression if used in automotive or industrial environments with potential load-dump events.

Does LM2575WT require an external catch diode, and what type is recommended?

Yes, LM2575WT requires an external Schottky catch diode connected between the OUTPUT pin and GND. The datasheet specifies MBR360 or equivalent (3A, 60V, low VF). Using a standard PN diode increases conduction losses and reduces efficiency below 75%; a properly rated Schottky diode ensures <0.5V forward drop and supports the 52kHz switching frequency without reverse recovery issues.

Can LM2575WT be used in a negative-output (inverting) configuration?

Yes, LM2575WT can be configured as a negative-output buck-boost converter per Figure 10 in the Micrel datasheet. In this topology, the GND pin becomes the negative output rail, and the OUTPUT pin connects to the inductor and diode anode. Output polarity reverses, enabling -1.23V to -37V generation. Layout must maintain strict ground separation between input and inverted output sections to avoid coupling noise into sensitive analog circuits.

What is the thermal resistance (θJA) of LM2575WT in typical PCB mounting?

For LM2575WT in TO-220 package mounted vertically on a PCB with ~4 square inches of copper area surrounding the leads, θJA is 45°C/W. With minimal copper (socket mount), it rises to 65°C/W. To sustain 1A continuous output at 40V input, ambient temperature must remain ≤60°C with adequate copper pour or external heatsink - otherwise thermal shutdown will activate due to junction temperature exceeding 125°C.

How does the ON/OFF pin function on LM2575WT, and what logic levels disable the output?

The ON/OFF pin on LM2575WT is active-low: pulling it below 0.8V (typical) enables regulation, while raising it above 2.2V (typical) forces the internal switch OFF and reduces quiescent current to ≤200µA. The pin draws ≤30µA when enabled and ≤10µA when disabled. No pull-up or pull-down resistor is required if driven directly by a microcontroller GPIO, but a 10kΩ pull-down ensures default ON behavior during MCU reset.