Microchip Technology LM2574-5.0YN

Overview

LM2574-5.0YN from Micrel, Inc. is a fixed-output 5.0V, 0.5A step-down (buck) switching regulator in an 8-pin plastic DIP package, featuring internal 52kHz oscillator, cycle-by-cycle current limiting, and thermal shutdown. It operates from 7V to 40V input and delivers ±4% output voltage accuracy across load and line variations. Used in on-card DC-DC conversion for industrial power supplies.

For engineers reviewing the LM2574-5.0YN datasheet, LM2574-5.0YN pinout, LM2574-5.0YN application, or LM2574-5.0YN equivalent, key selection criteria include guaranteed 0.5A output current, 52kHz fixed-frequency operation, standby current <200µA, and compatibility with standard off-the-shelf inductors and capacitors.

Technical Context

The LM2574-5.0YN integrates a PWM controller, power switch, error amplifier, 1.23V bandgap reference, and 52kHz oscillator into a single IC. Its feedback loop uses the internal 1.23V reference and external resistor divider only in adjustable versions; the -5.0YN variant routes FB internally to set 5.0V output directly.

Protection features include peak-current limiting (1.0A typical), thermal shutdown at ~150°C junction temperature, and ON/OFF logic control via pin 3. The device requires only four external components: input capacitor, output capacitor, diode, and inductor - no frequency compensation network needed.

Key Specifications

Pinout & Package

LM2574-5.0YN is housed in an 8-pin plastic DIP (N) package with 0.3" width and through-hole mounting. Pin thermal pad connection is not present; heat dissipation relies on PCB copper area under all pins.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2574H-5.0 and MC33063AP, the LM2574-5.0YN provides optimal balance of simplicity, cost, and performance for fixed 5V/0.5A applications - requiring only four passive components while maintaining tight output tolerance and robust protection without design overhead.

Availability

LM2574-5.0YN is available at Aetrix Electronics and suitable for industrial power rails, microcontroller core supplies, and POS terminal power requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM2574-5.0YN 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 analog, power management, and timing solutions before its acquisition by Microchip Technology in 2015.

The LM2574 product line was designed as a low-component-count, easy-to-use buck regulator family targeting cost-sensitive industrial, consumer, and embedded applications where simplicity and reliability outweigh advanced feature sets.

FAQ

What is the maximum input voltage rating for the LM2574-5.0YN?

The LM2574-5.0YN has an absolute maximum input voltage rating of 45V, but its recommended operating input voltage range is 7V to 40V DC. Operation within this 40V limit ensures guaranteed performance including ±4% output regulation, 0.5A output current, and thermal stability across the full –40°C to +85°C temperature range. Exceeding 40V may compromise long-term reliability even if below the 45V absolute maximum.

Does the LM2574-5.0YN require external feedback resistors to set its output voltage?

No, the LM2574-5.0YN does not require external feedback resistors. As a fixed-output variant, it internally connects the feedback (FB) pin to a precision 5.0V regulation node. This eliminates resistor selection errors, saves board space, and simplifies design compared to the adjustable LM2574 versions. The FB pin (pin 1) remains unused and should not be connected externally in the LM2574-5.0YN.

How does the ON/OFF pin function on the LM2574-5.0YN?

The ON/OFF pin (pin 3) of the LM2574-5.0YN enables hardware-controlled shutdown. Applying a logic-low voltage (<1.2V) activates regulation; applying logic-high (>2.2V) places the device in standby mode with quiescent current <200µA. The pin draws only 4–30µA, making it compatible with standard CMOS outputs. No pull-up or pull-down is required - the state is determined solely by the applied voltage level.

Can the LM2574-5.0YN be used with a 3.3V input supply?

No, the LM2574-5.0YN cannot operate from a 3.3V input. Its minimum operating input voltage is 7V, as specified in the datasheet's Operating Ratings and confirmed by dropout behavior in Typical Characteristics. At VIN < 7V, the internal switch cannot sustain regulation, resulting in uncontrolled output collapse. For 3.3V input applications, a different topology such as a buck-boost or low-VIN synchronous buck regulator is required.

What package type is used for the LM2574-5.0YN, and are there thermal considerations?

The LM2574-5.0YN uses an 8-pin plastic DIP (N) package with 0.3" width. It has no exposed thermal pad; thermal performance relies entirely on PCB copper area connected to all pins, especially pins 2 (SIG GND) and 4 (PWR GND). The junction-to-ambient thermal resistance is 85°C/W with ~1 in² of copper. For continuous 0.5A operation at high ambient temperatures, ensure adequate copper pour and avoid enclosing the device in thermally restrictive housings.