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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

Microchip Technology LM2574-3.3BN

Name: LM2574-3.3BN
Brand: Microchip Technology
SKU: LM2574-3.3BN
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LM2574-3.3BN

Manufacturer:: Microchip Technology

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 8-DIP (0.300", 7.62mm)

Datasheet:: LM2574-3.3BN.pdf

Description:: IC REG BUCK 3.3V 500MA 8PDIP

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Product details

Overview

LM2574-3.3BN from Texas Instruments is a step-down (buck) switching regulator IC delivering fixed 3.3 V output at up to 0.5 A, with 75% typical efficiency, 52 kHz fixed-frequency operation, and internal 135 V NPN switch. It is used in industrial power supplies and embedded microcontroller systems requiring compact, low-cost DC-DC conversion.

For engineers reviewing the LM2574-3.3BN datasheet, LM2574-3.3BN pinout, LM2574-3.3BN application, or LM2574-3.3BN equivalent, key selection criteria include input voltage range (4.75–40 V), dropout behavior under load, thermal shutdown threshold (150 °C), and compatibility with standard external diode/inductor/capacitor layouts.

Technical Context

The LM2574-3.3BN integrates a PWM controller, oscillator, error amplifier, and 135 V, 3.0 A NPN power transistor in a single SOIC-8 package. It operates in discontinuous conduction mode (DCM) at light loads and uses external compensation via a single feedback resistor divider.

It requires no external current-sense resistor and relies on cycle-by-cycle current limiting with foldback protection. The device lacks synchronous rectification and does not support adjustable output - only fixed 3.3 V versions are offered in the BN suffix variant.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 3.3 V ±2%, stable across line/load/temperature for powering 3.3 V logic rails.
Max Output Current	500 mA continuous, limited by internal switch R_DS(on) and thermal design of SOIC-8 package.
Input Voltage Range	4.75 V to 40 V - supports wide-input industrial and automotive battery-derived supplies.
Switching Frequency	52 kHz nominal - enables use of low-cost, high-inductance toroidal inductors and reduces EMI filtering complexity.
Efficiency	Up to 75% at 12 V_IN/3.3 V_OUT/300 mA - trade-off between cost, size, and thermal performance vs. modern synchronous buck ICs.
Thermal Shutdown	Activates at 150 °C junction temperature - protects device during overload or poor PCB heatsinking.

Pinout & Package

LM2574-3.3BN is housed in an 8-pin SOIC (Small Outline Integrated Circuit) package with exposed pad for thermal enhancement. Pin 1 is marked with a dot; pin numbering follows standard SOIC convention.

Pin/Terminal	Circuit Role	Design Meaning
1 (VIN)	Input voltage supply	Accepts 4.75–40 V DC; must be bypassed with ≥100 µF electrolytic capacitor near pin.
2 (GND)	Power ground	Common return for internal switch, control circuitry, and external diode cathode connection.
3 (OUT)	Switch node	Drives external catch diode anode and inductor; high dv/dt node requiring short PCB trace routing.
4 (FEEDBACK)	Output voltage sense	Internally tied to 3.3 V reference; unused in fixed-output version - left open or grounded per datasheet.
5 (ON/OFF)	Enable control	Logic-high (>2.5 V) enables regulation; logic-low (<1.3 V) disables output and reduces quiescent current to 75 µA.
6 (GND)	Power ground	Second GND pin for improved thermal and noise performance - must be connected to same ground plane as Pin 2.
7 (COMP)	Compensation node	Connects to external RC network for loop stability - required even in fixed-output configuration.
8 (VREF)	Internal reference	Provides 1.23 V reference for feedback comparator; not user-accessible in fixed-output variants.

Key Features

Feature	Design Value
Integrated 135 V NPN switch	Eliminates need for external high-voltage transistor - simplifies BOM and layout for 40 V max input designs.
Fixed 3.3 V output	Reduces component count by removing feedback resistors - ideal for cost-sensitive, volume OEM applications.
52 kHz switching frequency	Enables use of inexpensive, high-inductance inductors (e.g., 100–220 µH) and lowers core loss vs. higher-frequency alternatives.
Thermal shutdown + current limit	Provides self-protection without external sensing - improves reliability in unattended industrial environments.
Low quiescent current (75 µA)	Supports standby-mode operation in battery-backed systems where <100 µA sleep current is critical.

Applications

Industrial Sensor Node Power	Legacy Microcontroller Supply
Use Scenario: Powering 3.3 V RS-485 transceivers and analog sensor front-ends in factory-floor temperature/humidity nodes. IC Role / Device Role / Timing Role: Primary non-isolated DC-DC converter stepping down 24 V field bus to regulated 3.3 V rail. Use Value: Tolerates 24 V ±20% input variation and survives 40 V transients common in industrial wiring.	Use Scenario: Supplying legacy 3.3 V ARM7 or MSP430-based control modules in retrofit equipment. IC Role / Device Role / Timing Role: Fixed-output buck regulator replacing linear regulators to reduce heat in enclosed enclosures. Use Value: Delivers 500 mA at 75% efficiency - cuts thermal load by >60% versus 78L05 linear regulator at same load.
Point-of-Load for PLC I/O Modules	Automotive Body Control Unit (BCU)
Use Scenario: Generating local 3.3 V for digital isolators and FPGA configuration memory in modular PLC backplanes. IC Role / Device Role / Timing Role: Secondary regulator fed from 5 V or 12 V intermediate rail, providing clean logic supply. Use Value: Internal current limiting prevents latch-up during hot-plug insertion of I/O cards.	Use Scenario: Powering 3.3 V CAN transceivers and microcontrollers in 12 V automotive body electronics. IC Role / Device Role / Timing Role: Buck converter handling cold-crank (4.75 V) to load-dump (36 V) conditions per ISO 7637-2. Use Value: 40 V absolute maximum input rating meets automotive transient immunity requirements without external clamping.

Industrial Sensor Node Power

Legacy Microcontroller Supply

Use Scenario: Powering 3.3 V RS-485 transceivers and analog sensor front-ends in factory-floor temperature/humidity nodes.

IC Role / Device Role / Timing Role: Primary non-isolated DC-DC converter stepping down 24 V field bus to regulated 3.3 V rail.

Use Value: Tolerates 24 V ±20% input variation and survives 40 V transients common in industrial wiring.

Use Scenario: Supplying legacy 3.3 V ARM7 or MSP430-based control modules in retrofit equipment.

IC Role / Device Role / Timing Role: Fixed-output buck regulator replacing linear regulators to reduce heat in enclosed enclosures.

Use Value: Delivers 500 mA at 75% efficiency - cuts thermal load by >60% versus 78L05 linear regulator at same load.

Point-of-Load for PLC I/O Modules

Automotive Body Control Unit (BCU)

Use Scenario: Generating local 3.3 V for digital isolators and FPGA configuration memory in modular PLC backplanes.

IC Role / Device Role / Timing Role: Secondary regulator fed from 5 V or 12 V intermediate rail, providing clean logic supply.

Use Value: Internal current limiting prevents latch-up during hot-plug insertion of I/O cards.

Use Scenario: Powering 3.3 V CAN transceivers and microcontrollers in 12 V automotive body electronics.

IC Role / Device Role / Timing Role: Buck converter handling cold-crank (4.75 V) to load-dump (36 V) conditions per ISO 7637-2.

Use Value: 40 V absolute maximum input rating meets automotive transient immunity requirements without external clamping.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM2574H-3.3BN	Higher input voltage rating (60 V vs. 40 V); identical pinout, package, and output specs.	Better suited for 48 V telecom or heavy-duty vehicle systems where transients exceed 40 V.	Select LM2574H-3.3BN when input may exceed 40 V; otherwise LM2574-3.3BN is lower-cost and sufficient.
LM2596-3.3	Higher current (3 A), adjustable/fixed variants, 150 kHz switching - requires different inductor/capacitor values.	Used where higher output current or better efficiency at light loads is needed; not pin-compatible.	Choose LM2596-3.3 only if >500 mA output or improved light-load efficiency is required - redesign of passive components is mandatory.

Compared with LM2574H-3.3BN and LM2596-3.3, the LM2574-3.3BN offers optimal cost and simplicity for 3.3 V/500 mA applications within 40 V input limits, with proven thermal robustness in SOIC-8 industrial layouts.

Availability

LM2574-3.3BN is available at Aetrix Electronics and suitable for industrial sensor nodes, legacy microcontroller supplies, and PLC I/O modules requiring stable component supply and long-term manufacturability.

Supply support for LM2574-3.3BN 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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs.

The LM2574 series was designed for cost-effective, robust non-synchronous buck conversion in industrial and automotive power supplies where simplicity and reliability outweigh ultra-high efficiency demands.

FAQ

What is the maximum input voltage rating for the LM2574-3.3BN?

The LM2574-3.3BN has an absolute maximum input voltage rating of 40 V. Operation above this level risks permanent damage. It is rated for continuous operation from 4.75 V to 40 V, making it suitable for 24 V industrial systems and 12 V automotive applications with transient tolerance. Always observe derating guidelines in the official TI datasheet for LM2574-3.3BN.

Does the LM2574-3.3BN require external feedback resistors?

No, the LM2574-3.3BN does not require external feedback resistors because it is a fixed-output variant with internal resistor divider set to 3.3 V. The FEEDBACK pin is internally connected and must be left unconnected or grounded per TI's recommended layout for the LM2574-3.3BN. This eliminates tuning errors and reduces BOM count.

Can the LM2574-3.3BN be used in automotive applications?

Yes, the LM2574-3.3BN is suitable for automotive body electronics such as BCUs and lighting controllers, provided input transients comply with ISO 7637-2 Pulse 1/2a/5a. Its 4.75–40 V input range covers cold-crank to load-dump conditions. However, it is not AEC-Q100 qualified; for safety-critical systems, consult TI's automotive-grade alternatives to LM2574-3.3BN.

What type of external diode is recommended for the LM2574-3.3BN?

Texas Instruments recommends a fast-recovery or Schottky diode rated for ≥1 A average current and ≥60 V PIV, such as the 1N5822 or SB560. The diode connects between the OUT pin and GND, with its cathode to OUT. Using a diode with low forward voltage and fast reverse recovery minimizes conduction loss and improves efficiency in the LM2574-3.3BN circuit.

Is thermal management required for the LM2574-3.3BN at full 500 mA load?

Yes - at 500 mA output and 12 V input, the LM2574-3.3BN dissipates ~1.8 W. Adequate copper area (≥2 cm² per GND pin), thermal vias to inner layers, and optional small heatsink are recommended. The SOIC-8 package's θ_JA is 65 °C/W; without thermal relief, junction temperature may exceed 125 °C. Refer to layout guidance in the LM2574-3.3BN datasheet for reliable thermal design.

LM2574-3.3BN Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

Package/Case:: 8-DIP (0.300", 7.62mm)

Packaging:: Bulk

Product Status:: Obsolete

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Fixed

Number of Outputs:: 1

Voltage - Input (Min):: -

Voltage - Input (Max):: 40V

Voltage - Output (Min/Fixed):: 3.3V

Voltage - Output (Max):: -

Current - Output:: 500mA

Frequency - Switching:: 52kHz

Synchronous Rectifier:: No

Operating Temperature:: -40°C ~ 125°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 8-PDIP

LM2574-3.3BN FAQ

1.How can I place an order for LM2574-3.3BN through Aetrix?

Please submit a Request for Quotation (RFQ) for LM2574-3.3BN on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for LM2574-3.3BN reliable?

The price and inventory of LM2574-3.3BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2574-3.3BN is usually 5 days.

3.What payment methods are accepted for LM2574-3.3BN?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2574-3.3BN transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LM2574-3.3BN?

LM2574-3.3BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LM2574-3.3BN order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for LM2574-3.3BN?

For technical support, including LM2574-3.3BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2574-3.3BN requirements.

6.How does Aetrix verify that LM2574-3.3BN is sourced from the original manufacturer or authorized distributors?

All LM2574-3.3BN products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM2574-3.3BN meets industry standards.

7.What is the process for return or replacement of LM2574-3.3BN?

All LM2574-3.3BN units undergo pre-shipment inspection (PSI). If there is an issue with LM2574-3.3BN, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The LM2574-3.3BN part is unused and in its original packaging.

Return procedure for LM2574-3.3BN:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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