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onsemi LM2574N-3.3
- Part No.:
- LM2574N-3.3
- Manufacturer:
- onsemi
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LM2574N-3.3.pdf
- Description:
- IC REG BUCK BST 3.3V 500MA 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,993
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Product details
Overview
LM2574N-3.3 from Texas Instruments is a monolithic 0.5-A non-synchronous step-down (buck) DC-DC switching regulator with fixed 3.3-V output, 40-V maximum input voltage, 52-kHz internal oscillator, ±4% output voltage tolerance over line and load, and integrated thermal shutdown and cycle-by-cycle current limiting. It serves as an efficient replacement for linear regulators in industrial power supplies and embedded system rails.
For engineers reviewing the LM2574N-3.3 datasheet, pinout, applications, or equivalent options, key selection criteria include input voltage range (up to 40 V), output accuracy (±4%), standby current (50 μA), thermal performance (60.4°C/W RθJA in PDIP), and external component count (only 4 required).
Technical Context
The LM2574N-3.3 implements a fixed-frequency, pulse-width modulation (PWM) buck topology with an internal 52-kHz oscillator and non-synchronous NPN switch. Regulation is achieved via feedback comparison of output voltage against a 1.23-V internal bandgap reference, with error amplifier output driving the switch duty cycle.
It features TTL-compatible ON/OFF control (active-low enable), cycle-by-cycle current limiting (typ. 1 A peak), thermal shutdown, and built-in frequency compensation - eliminating need for external compensation components. The device operates across –40°C to +125°C junction temperature and requires no heatsink under typical PCB copper trace conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V ±4% over full line/load/temperature range - ensures stable logic rail for 3.3-V microcontrollers and FPGAs without trimming. |
| Max Input Voltage | 40 V - supports wide-input industrial and automotive-supplied systems without pre-regulation. |
| Output Current | 0.5 A continuous - sufficient for powering multiple low-power ICs or single mid-range MCU with peripherals. |
| Oscillator Frequency | 52 kHz (±10%) - enables use of low-cost, high-saturation-current off-the-shelf inductors and reduces EMI filtering complexity. |
| Standby Current | 50 μA typical at shutdown - enables low-power sleep modes in battery-backed or energy-conscious systems. |
| Thermal Resistance | 60.4°C/W RθJA (PDIP-8) - allows full 0.5-A operation at +70°C ambient with standard 2-layer PCB copper pour, no heatsink needed. |
| Efficiency | 72% at 12-V input / 0.5-A load - significantly reduces heat generation vs. linear regulators (e.g., >3 W less dissipation than LDO at same condition). |
Pinout & Package
LM2574N-3.3 is packaged in an 8-pin PDIP (Plastic Dual In-line Package) with 6.35 mm × 9.81 mm body size and through-hole mounting. Thermal performance relies on PWR_GND and SIG_GND pins connected to adequate PCB copper area.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 FB | Feedback sense input | Internally tied to output capacitor for fixed 3.3-V version; not used externally - simplifies layout and eliminates resistor divider errors. |
| 2 SIG_GND | Signal ground reference | Ground return for internal bandgap, error amp, and logic - must be routed separately from power ground to avoid noise coupling into regulation loop. |
| 3 ON/OFF | Enable control input | Active-low TTL-compatible shutdown pin; <1.2 V = ON, >1.4 V = OFF - enables system-level power sequencing and low-quiescent standby. |
| 4 PWR_GND | Power ground | High-current return path for switch emitter and input/output capacitors - requires short, low-inductance connection to minimize switching noise and thermal rise. |
| 5 VIN | Input supply | Collector node of internal NPN switch; accepts 4.75–40 V DC - must be bypassed with ≥22-μF electrolytic + optional ceramic capacitor near pin. |
| 6–8 NC | No internal connection | Unused pins; recommended to solder to PCB ground plane for mechanical stability and improved thermal conduction. |
| 7 OUTPUT | Switching node | Emitter of internal NPN transistor - connects directly to inductor and Schottky diode cathode; high dv/dt node requiring tight layout and minimal trace area. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed-output architecture | Eliminates external feedback resistors - reduces BOM count, layout sensitivity, and long-term drift from resistor aging or thermal mismatch. |
| Integrated protection | Combines cycle-by-cycle current limit (1 A typ.), thermal shutdown, and undervoltage lockout - prevents damage during overload, short-circuit, or brownout without external circuitry. |
| Low-component design | Requires only 4 external parts: input cap, output cap, inductor, and catch diode - accelerates prototyping and improves reliability vs. discrete switcher designs. |
| Internal frequency compensation | Enables stable operation with standard output capacitors (e.g., aluminum or tantalum) - avoids complex type-II/type-III compensation network tuning. |
| TTL shutdown interface | Supports direct connection to microcontroller GPIO or logic-level sequencer - enables precise power-on reset timing and coordinated system sleep/wake transitions. |
Applications
| Industrial Sensor Node Power | Embedded MCU Core Rail |
|---|---|
Use Scenario: Powering a wireless sensor node with 3.3-V MCU, RF transceiver, and analog front-end from a 12–24-V industrial bus. IC Role / Device Role / Timing Role: Primary step-down regulator converting unregulated bus voltage to clean, regulated 3.3-V supply. Use Value: Delivers 0.5 A at 72% efficiency with no heatsink, enabling compact enclosure design and extended battery life when paired with sleep-mode MCU. |
Use Scenario: Generating core voltage for ARM Cortex-M4 microcontroller and associated peripherals in a programmable logic controller (PLC) module. IC Role / Device Role / Timing Role: Main DC-DC converter supplying stable 3.3-V rail with fast transient response to CPU load changes. Use Value: ±4% output tolerance and integrated thermal protection ensure reliable operation across –40°C to +85°C industrial temperature range without derating. |
| POS Terminal Power Supply | Legacy Equipment Retrofit |
Use Scenario: Replacing aging linear regulators in point-of-sale terminals powered from 12-V wall adapters. IC Role / Device Role / Timing Role: High-efficiency buck regulator reducing board-level heat and improving adapter utilization. Use Value: 50-μA standby current and 52-kHz fixed frequency simplify EMI compliance testing and reduce thermal management cost vs. linear solution. |
Use Scenario: Upgrading obsolete 78L33 linear regulators in legacy test equipment with higher input voltage tolerance. IC Role / Device Role / Timing Role: Drop-in compatible switching alternative accepting up to 40-V input while maintaining same 3.3-V output and pin-compatible footprint (PDIP-8). Use Value: Enables continued use of existing PCB layout and connectors while supporting wider input range and lower thermal stress on board. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2575T-3.3 | Higher 1-A output current, TO-220 package, 52-kHz frequency, same 3.3-V fixed output and pinout family. | Preferred where >0.5-A load or higher thermal margin is required; TO-220 enables higher ambient operation but requires different PCB footprint. | Select LM2575T-3.3 when load exceeds 0.5 A or when TO-220 mounting and enhanced thermal dissipation are available. |
| MP1584EN-LF-Z | 40-V input, 3-A output, 1.5-MHz switching frequency, adjustable output (requires external resistors), smaller SOIC-8 package. | Suitable for space-constrained designs needing higher current or faster transient response; requires feedback divider and may need additional EMI filtering due to higher frequency. | Choose MP1584EN-LF-Z for compact, high-current applications where board area is limited and adjustable output flexibility is acceptable. |
Compared with LM2574N-3.3, LM2575T-3.3 offers double the output current in a thermally robust TO-220 package but increases board area and cost, while MP1584EN-LF-Z delivers 6× higher current and 29× higher switching frequency in SOIC-8 - enabling smaller magnetics but demanding tighter layout and added filtering.
Availability
LM2574N-3.3 is available at Aetrix Electronics and suitable for industrial automation, embedded computing, and point-of-sale equipment requiring stable component supply, long-lifecycle support, and proven reliability in harsh environments.
Supply support for LM2574N-3.3 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 LM2574x SIMPLE SWITCHER® series was designed specifically for cost-sensitive, medium-power DC-DC conversion in industrial, telecom, and consumer applications - prioritizing ease of use, minimal external components, and robust protection without requiring design expertise in switch-mode power supply theory.
FAQ
What is the maximum input voltage rating for LM2574N-3.3?
The LM2574N-3.3 has a maximum input voltage rating of 40 V, as specified in its Absolute Maximum Ratings table. This applies to the standard LM2574 variant; the HV version (LM2574HV) supports up to 60 V. Operation above 40 V risks permanent damage to the LM2574N-3.3, and the device includes internal undervoltage lockout to prevent startup below ~4.75 V.
Does LM2574N-3.3 require external compensation components?
No, the LM2574N-3.3 integrates full frequency compensation internally. Its fixed-frequency PWM architecture and internal error amplifier are designed to operate stably with standard output capacitors (e.g., aluminum or tantalum) and the recommended external inductor and diode - eliminating the need for external RC networks or compensation capacitors typically required in more complex controllers.
Can LM2574N-3.3 be used in a buck-boost configuration?
Yes, the LM2574N-3.3 can be configured as a positive-to-negative buck-boost converter per TI's documented typical application circuits. In this topology, the OUTPUT pin drives the inductor, the diode is reversed, and the output is taken across the capacitor referenced to VIN. Output polarity is inverted, and regulation accuracy remains within ±4%, though efficiency and ripple characteristics differ from standard buck operation.
What is the thermal resistance (RθJA) of LM2574N-3.3 in its PDIP package?
The LM2574N-3.3 in the 8-pin PDIP package has a junction-to-ambient thermal resistance (RθJA) of 60.4°C/W, measured on a standard JEDEC 4-layer test board. This value assumes proper PCB copper pour on both signal and power ground planes. With 0.5-A load and 12-V input, junction temperature rise is approximately 22°C above ambient - well within the 125°C max operating limit.
How does the ON/OFF pin function on LM2574N-3.3?
The ON/OFF pin on LM2574N-3.3 is an active-low enable input: pulling it below 1.2 V (typically to GND) enables regulation, while raising it above 1.4 V disables the switcher and places LM2574N-3.3 in standby mode with 50-μA typical quiescent current. The pin is TTL-compatible and must never be left floating to prevent erratic operation.
LM2574N-3.3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, Buck-Boost
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.75V
- 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
LM2574N-3.3 FAQ
1.How can I place an order for LM2574N-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2574N-3.3 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 LM2574N-3.3 reliable?
The price and inventory of LM2574N-3.3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2574N-3.3 is usually 5 days.
3.What payment methods are accepted for LM2574N-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2574N-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2574N-3.3?
LM2574N-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2574N-3.3 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 LM2574N-3.3?
For technical support, including LM2574N-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2574N-3.3 requirements.
6.How does Aetrix verify that LM2574N-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2574N-3.3 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 LM2574N-3.3 meets industry standards.
7.What is the process for return or replacement of LM2574N-3.3?
All LM2574N-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2574N-3.3, 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 LM2574N-3.3 part is unused and in its original packaging.
Return procedure for LM2574N-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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