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Microchip Technology LM2576-3.3BU
- Part No.:
- LM2576-3.3BU
- Manufacturer:
- Microchip Technology
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LM2576-3.3BU.pdf
- Description:
- IC REG BUCK 3.3V 3A TO263-5
- Quantity:
- Payment:
- Shipping:
Inventory:2,147
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Product details
Overview
LM2576-3.3BU from Micrel is a fixed-output 3.3V, 3A step-down (buck) switching regulator in TO-263-5 package, featuring 52kHz fixed-frequency operation, ±3% output voltage tolerance over line/load/temperature, and integrated thermal shutdown and cycle-by-cycle current limiting. It replaces linear regulators in industrial power supplies, embedded controllers, and DC-DC conversion stages requiring high efficiency and minimal external components.
For engineers reviewing the LM2576-3.3BU datasheet, LM2576-3.3BU pinout, LM2576-3.3BU application, or LM2576-3.3BU equivalent, key selection criteria include input voltage range (4–40V), guaranteed 3A output current, standby quiescent current <200µA, and compatibility with standard off-the-shelf inductors for rapid design implementation.
Technical Context
The LM2576-3.3BU integrates a 3A NPN switch, 1.23V bandgap reference, error amplifier, 52kHz oscillator, and thermal/current protection circuitry in a monolithic buck controller architecture. Its fixed 3.3V output eliminates external feedback resistors, simplifying layout and improving stability across temperature and load variations.
Operation relies on pulse-width modulation with internal frequency compensation and fixed duty-cycle control logic. The ON/OFF pin enables external logic-level shutdown with <200µA standby current, while saturation voltage of ≤2.0V at 3A ensures low conduction loss under full load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±3% over –40°C to +85°C, 0.5–3A load, 6–40V input - ensures stable rail for 3.3V microcontrollers and FPGAs without trimming. |
| Max Output Current | 3A continuous - supports single-rail power for mid-power embedded systems without external current boosting. |
| Input Voltage Range | 4V to 40V - accommodates wide-input industrial, automotive, and telecom supply rails including unregulated 24V and 36V sources. |
| Switching Frequency | 52kHz ±10% - enables use of low-cost, high-saturation-current toroidal inductors and reduces EMI filtering complexity vs. MHz-range converters. |
| Efficiency | 75% at 12VIN/3.3VOUT/3A - significantly reduces thermal dissipation versus linear regulators, often eliminating need for heatsinks. |
| Standby Current | <200µA when ON/OFF pin = 5V - enables low-power sleep modes in battery-backed or energy-conscious applications. |
| Protection Features | Thermal shutdown + cycle-by-cycle current limit - prevents damage during overload, short-circuit, or ambient overheating without external sensing. |
Pinout & Package
LM2576-3.3BU uses the 5-lead TO-263 (D²PAK) surface-mount package with exposed thermal pad for enhanced heat dissipation. Pin 1 is VIN, Pin 2 is OUTPUT, Pin 3 is GND, Pin 4 is FEEDBACK (internally tied to 3.3V reference), and Pin 5 is ON/OFF.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - VIN | Unregulated input supply connection | Accepts 4–40V DC; requires ≥100µF input capacitor to suppress ripple and sustain minimum input during high-current pulses. |
| 2 - OUTPUT | Regulated 3.3V switching node | Drives external inductor and catch diode; peak current capability up to 3A; connects to output filter capacitor (≥330µF recommended). |
| 3 - GND | Power and signal ground reference | Must be low-impedance connection to PCB ground plane; shared return path for input cap, output cap, and feedback network. |
| 4 - FEEDBACK | Internal 3.3V reference tap | Internally connected to 3.3V output; no external resistor divider required - eliminates calibration drift and improves accuracy vs. adjustable variants. |
| 5 - ON/OFF | Logic-controlled enable/disable input | Active-low shutdown: ≤0.8V = ON, ≥2.2V = OFF; draws ≤30µA when enabled, <200µA in standby - ideal for MCU-controlled power sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 3.3V output | Eliminates external feedback resistors, reducing BOM count, layout area, and potential tolerance-induced output error. |
| 52kHz fixed-frequency oscillator | Enables predictable EMI profile and simplifies filter design using widely available, low-DCR power inductors (e.g., 330µH). |
| Integrated thermal shutdown | Automatically disables switching if junction temperature exceeds ~150°C, protecting device and system during sustained overload or poor heatsinking. |
| Cycle-by-cycle current limiting | Clamps peak switch current to ~5.8A, preventing MOSFET or inductor saturation during startup, short circuits, or transient overloads. |
| Low standby quiescent current | Supports ultra-low-power system states: <200µA draw in OFF mode allows battery-powered devices to maintain weeks of shelf life. |
Applications
| Industrial PLC I/O Modules | Embedded Microcontroller Power Rails |
|---|---|
|
Use Scenario: Powering isolated digital I/O channels in programmable logic controllers operating from 24V DC field buses. IC Role / Device Role / Timing Role: Primary 3.3V buck regulator supplying FPGA configuration logic, ADC/DAC interfaces, and optocoupler drivers. Use Value: Delivers stable 3.3V at up to 3A with ±3% regulation across –40°C to +85°C ambient, enabling reliable operation in harsh factory environments. |
Use Scenario: Generating clean 3.3V supply for ARM Cortex-M or RISC-V microcontrollers in edge sensor nodes. IC Role / Device Role / Timing Role: Main system regulator converting wide-input 9–36V DC to precise 3.3V core voltage with low-noise output. Use Value: Achieves 75% efficiency at full load and <200µA shutdown current, extending battery life while maintaining tight voltage tolerance for sensitive digital logic. |
| Telecom Remote Radio Units | Test & Measurement Equipment |
|
Use Scenario: Providing regulated 3.3V bias for RF front-end ICs and clock buffers in outdoor small-cell base stations. IC Role / Device Role / Timing Role: Secondary buck stage stepping down intermediate 12V rail to low-noise 3.3V for analog/RF subsystems. Use Value: Fixed 3.3V output eliminates resistor drift concerns; thermal shutdown protects against enclosure overheating in sealed enclosures. |
Use Scenario: Supplying precision 3.3V reference rails for data acquisition modules and signal generators. IC Role / Device Role / Timing Role: High-stability DC-DC converter powering analog front-ends, DACs, and timing ICs requiring low ripple and fast transient response. Use Value: 52kHz switching frequency minimizes interference with sensitive analog measurements; 3A capability supports multi-channel simultaneous sampling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2576-3.3T | Same electrical specs, but TO-220-5 through-hole package with higher θJA (65°C/W vs. 45°C/W for TO-263) | Requires manual soldering and larger board area; less suitable for automated SMT production or space-constrained designs | Select LM2576-3.3T only when through-hole assembly or vertical heatsink mounting is required. |
| MP1584EN-LF-Z | 40V input, 3A, adjustable output (1.23–28V), 1.5MHz switching, smaller SOIC-8 package, no ON/OFF pin | Lacks enable control and fixed 3.3V option; requires external feedback resistors and higher-frequency magnetics | Choose MP1584EN-LF-Z when board space is critical and adjustable output or higher frequency is acceptable. |
Compared with LM2576-3.3T, the LM2576-3.3BU offers superior thermal performance in SMT layouts; compared with MP1584EN-LF-Z, it provides plug-and-play 3.3V regulation with built-in enable and lower EMI, at the cost of larger footprint and lower switching frequency.
Availability
LM2576-3.3BU is available at Aetrix Electronics and suitable for industrial automation, embedded computing, and telecom infrastructure requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM2576-3.3BU 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 mixed-signal ICs before its acquisition by Microchip Technology in 2015.
The LM2576 series was designed as a high-efficiency, easy-to-use replacement for three-terminal linear regulators in medium-power DC-DC conversion, targeting cost-sensitive industrial and embedded applications.
FAQ
What is the maximum input voltage rating for the LM2576-3.3BU?
The LM2576-3.3BU has an absolute maximum input voltage rating of 45V, with recommended continuous operation up to 40V. Exceeding 40V risks exceeding internal transistor breakdown limits and may trigger thermal shutdown or permanent damage. For reliable long-term operation, keep input within 4–40V as specified in the Electrical Characteristics table.
Does the LM2576-3.3BU require external feedback resistors?
No, the LM2576-3.3BU does not require external feedback resistors. It is a fixed-output variant with internal feedback tied to the 3.3V reference, unlike the adjustable LM2576 versions. Pin 4 (FEEDBACK) is internally connected and must not be externally modified - doing so will disrupt regulation and may cause output instability.
What is the thermal resistance (θJA) of the LM2576-3.3BU in typical PCB layout?
The LM2576-3.3BU in TO-263-5 package has a typical junction-to-ambient thermal resistance (θJA) of 45°C/W when mounted on a PCB with approximately 1 square inch of copper surrounding the leads. This value assumes proper thermal pad soldering and is critical for calculating maximum allowable power dissipation at elevated ambient temperatures.
Can the LM2576-3.3BU be used in negative-output (inverting) configurations?
Yes, the LM2576-3.3BU can be configured as a positive-to-negative inverting buck-boost converter per the manufacturer's Application Note AN-118. In this topology, the device regulates a negative output voltage (e.g., –3.3V) using standard external components, though output current capability and efficiency are reduced compared to standard buck operation.
What is the minimum recommended input capacitance for stable operation of the LM2576-3.3BU?
The LM2576-3.3BU requires a minimum 100µF aluminum electrolytic capacitor at the VIN pin, rated for ≥50V, to ensure stable operation and suppress input ripple during high-current switching transients. Lower capacitance increases input voltage sag and may cause dropout or erratic regulation, especially at high load currents and low input voltages.
LM2576-3.3BU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 3A
- Frequency - Switching:
- 52kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263-5
LM2576-3.3BU FAQ
1.How can I place an order for LM2576-3.3BU through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2576-3.3BU 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 LM2576-3.3BU reliable?
The price and inventory of LM2576-3.3BU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2576-3.3BU is usually 5 days.
3.What payment methods are accepted for LM2576-3.3BU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2576-3.3BU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2576-3.3BU?
LM2576-3.3BU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2576-3.3BU 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 LM2576-3.3BU?
For technical support, including LM2576-3.3BU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2576-3.3BU requirements.
6.How does Aetrix verify that LM2576-3.3BU is sourced from the original manufacturer or authorized distributors?
All LM2576-3.3BU 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 LM2576-3.3BU meets industry standards.
7.What is the process for return or replacement of LM2576-3.3BU?
All LM2576-3.3BU units undergo pre-shipment inspection (PSI). If there is an issue with LM2576-3.3BU, 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 LM2576-3.3BU part is unused and in its original packaging.
Return procedure for LM2576-3.3BU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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