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Texas Instruments LM2678SX-3.3
- Part No.:
- LM2678SX-3.3
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2678SX-3.3.pdf
- Description:
- IC REG BUCK 3.3V 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:1,977
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Product details
Overview
LM2678SX-3.3 from Texas Instruments is a monolithic 5A step-down (buck) DC/DC voltage regulator with fixed 3.3V output, 260 kHz internal oscillator, 120 mΩ DMOS power switch, and wide 8V–40V input range. It delivers high efficiency up to 92% and ±2% output tolerance over −40°C to +125°C junction temperature, used in industrial power supplies and embedded system pre-regulation.
For engineers reviewing the LM2678SX-3.3 datasheet, LM2678SX-3.3 pinout, LM2678SX-3.3 application, or LM2678SX-3.3 equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternatives, and supply-chain support for production deployment.
Technical Context
The LM2678SX-3.3 implements a fixed-frequency PWM buck controller with internal 260 kHz oscillator and cycle-by-cycle current limiting. Its DMOS power switch features 120 mΩ typical RDS(ON), enabling 5A continuous output with thermal shutdown and ON/OFF control.
It operates in continuous conduction mode with duty cycle up to 91%, uses external boost capacitor for gate drive enhancement, and relies on feedback pin (FB) tied directly to output for regulation-no external resistors required due to internal voltage divider for 3.3V fixed output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±2% over full line/load/temperature range-ensures stable logic rail for microcontrollers and FPGAs without trimming. |
| Max Output Current | 5A continuous-supports high-current digital loads like SoCs, DSPs, or multi-rail PMIC front-ends. |
| Input Voltage Range | 8V to 40V-compatible with 12V/24V industrial buses, battery systems, and unregulated AC/DC outputs. |
| Switching Frequency | 260 kHz ±11%-enables use of standard off-the-shelf inductors and balances EMI vs. efficiency trade-offs. |
| Efficiency | Up to 92% at 12VIN/5A-reduces thermal load and eliminates need for heatsinks in many 5A applications. |
| Quiescent Current | 50 μA in standby (ON/OFF = 0V)-enables low-power sleep modes in battery-backed or energy-sensitive systems. |
| RDS(ON) | 120 mΩ typical-minimizes conduction loss and improves full-load efficiency versus higher-RDS(ON) alternatives. |
Pinout & Package
LM2678SX-3.3 is packaged in TO-220-7 (Package Number NDZ0007B), with exposed tab thermally connected to Pin 9 (GND). The package supports vertical mounting with ½-inch leads soldered to ≥4 in² copper area for θJA = 45°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VSW) | Switch Node | Drives external inductor; swings between VIN and ~−0.5V during OFF-time-requires low-inductance layout and Schottky catch diode. |
| 2 (VIN) | Power Input | Accepts 8V–40V; must be bypassed with low-ESR capacitor near pin to suppress switching transients. |
| 3 (CBOOST) | Bootstrap Capacitor Terminal | Connects 0.01 μF ceramic cap to VSW to generate gate-drive voltage >VIN for full MOSFET enhancement. |
| 4,5,6,7 (GND) | Ground Reference | Four dedicated GND pins reduce ground impedance; all must connect to low-impedance PCB ground plane. |
| 8 (FB) | Feedback Input | Internally biased to 3.3V reference; direct connection to output enables fixed 3.3V regulation-no resistor network needed. |
| 9 (ON/OFF) | Enable Control | Logic-level input: <0.8V disables regulator (50 μA IQ); >2.0V enables operation-supports microcontroller sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120 mΩ DMOS Switch | Eliminates external high-side MOSFET and driver, reducing BOM count and layout complexity for 5A buck designs. |
| Fixed 3.3V Output with ±2% Tolerance | Guarantees compliance with 3.3V logic supply standards (e.g., PCIe, USB, ARM cores) across temperature and load. |
| 260 kHz Fixed-Frequency Oscillator | Enables predictable EMI filtering and simplifies inductor selection using TI-recommended parts from Renco, Pulse, Coilcraft. |
| Thermal Shutdown & Cycle-by-Cycle Current Limit | Protects against overload, short-circuit, and PCB overheating-no external protection circuitry required for robust field operation. |
| ON/OFF Pin with 50 μA Standby Current | Supports system-level power gating and deep-sleep states while maintaining fast wake-up (<100 μs) without external bias circuits. |
Applications
| Industrial PLC Power Supply | Automotive Body Control Module |
|---|---|
|
Use Scenario: Converts 24V vehicle battery or 24V industrial bus to clean 3.3V for MCU, CAN transceivers, and sensors. IC Role / Device Role / Timing Role: Primary step-down regulator delivering regulated 3.3V rail with high immunity to input transients and load steps. Use Value: 92% peak efficiency minimizes heat rise in sealed enclosures; 8V–40V input handles cold-crank (6.5V) and load-dump (40V+) events per ISO 7637-2. |
Use Scenario: Powers 3.3V domain in body control units managing door locks, lighting, and HVAC interfaces. IC Role / Device Role / Timing Role: High-current pre-regulator feeding LDOs or powering mixed-signal ASICs requiring stable 3.3V under varying load. Use Value: Built-in thermal shutdown and current limit ensure fault resilience during motor stall or wiring shorts-no external protection needed. |
| Medical Diagnostic Equipment | Networking Edge Router |
|
Use Scenario: Supplies 3.3V to FPGA-based imaging processing modules in portable ultrasound or patient monitors. IC Role / Device Role / Timing Role: Main DC/DC converter providing low-noise, high-reliability 3.3V rail with tight ±2% regulation for ADC references and clock buffers. Use Value: 260 kHz fixed frequency allows deterministic EMI filtering; 5A capability supports burst-mode processing without voltage droop. |
Use Scenario: Generates 3.3V for Ethernet PHYs, packet processors, and memory in compact edge routers with limited board space. IC Role / Device Role / Timing Role: Efficient intermediate regulator stepping down 12V/48V backplane voltage to 3.3V logic rails. Use Value: TO-220-7 package with exposed GND tab enables direct heatsinking to chassis-critical for fanless, high-density deployments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678T-3.3 | Same silicon, TO-220-5 package (no separate CBOOST pin); single GND pin; higher θJA (65°C/W). | Limited layout flexibility-requires external bootstrap capacitor routing; less suitable for high-reliability thermal designs. | Select LM2678SX-3.3 when board-level thermal management demands lowest possible θJA and dedicated boost terminal. |
| LM2596T-3.3 | 3A rated, 150 kHz oscillator, 0.22 Ω RDS(ON); no CBOOST pin; lower max input (40V same, but lower efficiency at 5A). | Not suitable for sustained 5A loads-derating required; lower efficiency increases thermal stress in enclosed systems. | Choose LM2678SX-3.3 where full 5A capability, 92% efficiency, and robust thermal performance are mandatory. |
Compared with LM2678T-3.3 and LM2596T-3.3, the LM2678SX-3.3 offers superior thermal resistance (45°C/W vs. 65°C/W), integrated CBOOST terminal for reliable gate drive, and verified 5A continuous operation-making it the only option among the three qualified for high-power, thermally constrained industrial applications.
Availability
LM2678SX-3.3 is available at Aetrix Electronics and suitable for industrial PLC power supplies, automotive body control modules, and medical diagnostic equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LM2678SX-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 ICs, with decades of expertise in high-efficiency DC/DC conversion.
The LM2678 series belongs to TI's SIMPLE SWITCHER® family-designed specifically for ease-of-use, minimal external component count, and robust performance in industrial, automotive, and medical power applications.
FAQ
What is the maximum input voltage rating for LM2678SX-3.3?
The absolute maximum input voltage for LM2678SX-3.3 is 45V, but the recommended operating range is 8V to 40V. Exceeding 40V risks violating the device's safe operating area, especially under transient conditions. The LM2678SX-3.3 datasheet specifies 40V as the upper limit for guaranteed performance across temperature and load, aligning with its use in 24V industrial and automotive systems.
Does LM2678SX-3.3 require external feedback resistors?
No, LM2678SX-3.3 does not require external feedback resistors. It is a fixed-output variant with internal resistor divider setting the regulated output to 3.3V. The FB pin connects directly to the output node, eliminating tuning components and ensuring ±2% accuracy without calibration-this is confirmed in the Electrical Characteristics table for LM2678-3.3 in the official TI datasheet.
What package type is used by LM2678SX-3.3?
LM2678SX-3.3 uses the TO-220-7 package (TI Package Number NDZ0007B), featuring seven leads including four dedicated GND pins and a separate CBOOST terminal. This package provides enhanced thermal performance (θJA = 45°C/W with 4 in² copper) and simplified layout versus the 5-pin TO-220 variant, as documented in the Connection Diagrams section of the LM2678 datasheet.
Can LM2678SX-3.3 operate with an input voltage below 8V?
No, LM2678SX-3.3 is not specified to operate below 8V input. The Operating Ratings table explicitly defines 8V as the minimum supply voltage. Below this threshold, the internal bias circuitry cannot sustain regulation, and the output will drop out of specification-even if the switch remains functional. This limitation is inherent to the LM2678SX-3.3 architecture and applies across the full temperature range.
What is the purpose of the CBOOST pin on LM2678SX-3.3?
The CBOOST pin on LM2678SX-3.3 connects a 0.01 μF ceramic capacitor to the VSW node to generate a boosted gate-drive voltage above VIN, ensuring full enhancement of the internal DMOS switch. This reduces RDS(ON) and conduction losses-directly enabling the LM2678SX-3.3 to achieve up to 92% efficiency at 5A. The pin is exclusive to the SX variant and is not present on the 5-pin T-package versions.
LM2678SX-3.3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 5A
- Frequency - Switching:
- 260kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-7)
LM2678SX-3.3 FAQ
1.How can I place an order for LM2678SX-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678SX-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 LM2678SX-3.3 reliable?
The price and inventory of LM2678SX-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 LM2678SX-3.3 is usually 5 days.
3.What payment methods are accepted for LM2678SX-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2678SX-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678SX-3.3?
LM2678SX-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678SX-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 LM2678SX-3.3?
For technical support, including LM2678SX-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678SX-3.3 requirements.
6.How does Aetrix verify that LM2678SX-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2678SX-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 LM2678SX-3.3 meets industry standards.
7.What is the process for return or replacement of LM2678SX-3.3?
All LM2678SX-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2678SX-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 LM2678SX-3.3 part is unused and in its original packaging.
Return procedure for LM2678SX-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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