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Texas Instruments LM2679SX-3.3
- Part No.:
- LM2679SX-3.3
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2679SX-3.3.pdf
- Description:
- IC REG BUCK 3.3V 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:4,285
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Product details
Overview
LM2679SX-3.3 from Texas Instruments is a monolithic 5A step-down (buck) switching voltage regulator with fixed 3.3V output, 8V–40V input range, 260 kHz fixed-frequency oscillator, 120 mΩ DMOS power switch, and ±2% output tolerance over full line/load/temperature. It delivers high-efficiency power conversion in industrial DC-DC pre-regulator and battery charger applications.
For engineers reviewing the LM2679SX-3.3 datasheet, LM2679SX-3.3 pinout, LM2679SX-3.3 application, or LM2679SX-3.3 equivalent, key selection criteria include verified 5A continuous output capability, resistor-programmable current limit (3A–7A), softstart timing control, thermal shutdown protection, and compatibility with standard off-the-shelf inductors and low-ESR output capacitors.
Technical Context
The LM2679SX-3.3 integrates a PWM controller, 120 mΩ DMOS power switch, and internal 260 kHz oscillator to implement a synchronous-buck topology without external gate drivers. Its feedback loop uses a precision 1.21V reference and high-gain amplifier referenced to the FB pin, enabling stable regulation with minimal external compensation.
Current limiting is implemented via an adjustable peak-switch-current threshold set by RADJ (e.g., 5.6 kΩ yields ~6.3 A), while softstart is controlled by a linear ramp on the SS pin driven by a 3.7 µA internal current source. Thermal shutdown activates at TJ ≥ 165°C, and the device operates across −40°C to +125°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V ±2% over −40°C to +125°C, 100 mA–5 A load, 8V–40V input - ensures stable logic supply for FPGA, microcontroller, or DSP core rails. |
| Input Voltage Range | 8 V to 40 V - supports wide-range industrial, automotive, and telecom input sources including unregulated 12V/24V/36V bus systems. |
| Switching Frequency | 260 kHz (±11%) - enables use of compact, standardized inductors (e.g., 10–22 µH) and reduces EMI compared to higher-frequency alternatives. |
| Peak Switch Current Limit | Programmable 3 A–7 A via RADJ resistor - allows optimization of external inductor/diode sizing for fault robustness without overdesign. |
| Efficiency | Up to 92% (typ. 82% @ 12VIN/5A) - minimizes thermal load and improves system-level power density in enclosed or convection-cooled enclosures. |
| Thermal Resistance (θJA) | 26°C/W (KTW package, 7.4× copper area) - enables 5A operation without external heatsink under defined PCB layout conditions. |
| Quiescent Current | 6 mA max @ VIN = 40 V - maintains low standby loss in always-on systems such as remote sensors or IoT edge nodes. |
Pinout & Package
LM2679SX-3.3 is packaged in the KTW (DDPAK-7) thermally enhanced surface-mount package (Package Number KTW0007B), featuring exposed die attach pad for direct PCB thermal coupling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW | Switch Node | Drives external inductor; swings between VIN and −0.5 V (Schottky drop); requires low-inductance routing to minimize ringing. |
| VIN | Power Input | Supplies internal bias and switch driver; must be bypassed with ≥3×15 µF/50 V ceramic + bulk capacitor near pin. |
| CBOOST | Bootstrap Capacitor Terminal | Connects to VSW; 0.01 µF/50 V ceramic provides gate overdrive to reduce RDS(ON) and improve efficiency. |
| GND | Power Ground | Common return for switch, feedback, and softstart; requires low-impedance ground plane to suppress noise coupling. |
| CURRENT ADJ | Current Limit Programming | Accepts RADJ resistor to ground; sets peak switch current per ICL = 37,125 / RADJ (Ω) in amperes. |
| FB | Feedback Input | Monitors regulated output; internally connected to 3.3V divider - no external resistors required for fixed-output version. |
| SOFTSTART | Softstart Control | Accepts external capacitor to ground; controls startup slew rate and limits inrush current during power-on. |
Key Features
| Feature | Design Value |
|---|---|
| Resistor-Programmable Current Limit | Enables precise fault-current tailoring (3–7 A) using single RADJ resistor - avoids oversized magnetics and diodes in partial-load applications. |
| Integrated 260 kHz Oscillator | Eliminates need for external timing components; ensures consistent switching frequency across temperature and input voltage for predictable EMI filtering. |
| Softstart with External Timing Capacitor | Prevents input surge current and output overshoot during turn-on - critical for hot-swap and battery-powered systems. |
| Thermal Shutdown Protection | Halts switching when junction temperature exceeds ~165°C - protects IC and downstream circuitry during overload or poor heatsinking. |
| High-Efficiency DMOS Power Switch | 120 mΩ RDS(ON) reduces conduction losses at 5A, enabling >90% efficiency with proper layout and component selection. |
Applications
| Industrial DC-DC Pre-regulator | Battery Charger Front-End |
|---|---|
Use Scenario: Converts unregulated 24V industrial bus to stable 3.3V for MCU, Ethernet PHY, or sensor interface circuits. IC Role / Device Role / Timing Role: Primary buck regulator delivering tightly regulated 3.3V at up to 5A with ±2% accuracy and fast transient response. Use Value: Replaces inefficient linear regulators, reducing heat generation by >70% and eliminating need for large heatsinks in DIN-rail mounted controllers. | Use Scenario: Steps down variable 12–36V battery pack voltage to charge Li-ion or LiFePO4 cell management ICs requiring clean 3.3V bias. IC Role / Device Role / Timing Role: Constant-voltage stage in multi-stage charging architecture; handles wide-input transients during battery insertion or load dump. Use Value: Maintains regulation during input dips and surges common in vehicle/marine battery systems, ensuring reliable BMS communication. |
| Embedded System Power Supply | Telecom Line Card Bias |
Use Scenario: Powers FPGA configuration memory, I/O banks, and peripheral interfaces in fanless embedded gateways. IC Role / Device Role / Timing Role: Main 3.3V rail generator with softstart and thermal protection - supports cold-start and extended ambient temperature operation. Use Value: Delivers full 5A output at 125°C junction temperature using only PCB copper area (no heatsink), simplifying mechanical design. | Use Scenario: Provides isolated 3.3V bias for optical transceiver modules and SERDES interfaces on telecom line cards. IC Role / Device Role / Timing Role: High-reliability secondary regulator fed from intermediate 12V or 24V backplane supply. Use Value: Achieves <1% output ripple with recommended COUT (2×180 µF/16V), meeting jitter-sensitive SerDes power integrity requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678-3.3 | Same pinout, identical 3.3V fixed output, but lacks adjustable current limit and softstart; 5A rating with 150 mΩ RDS(ON). | No programmable fault current or controlled startup - unsuitable where inrush limiting or custom overcurrent protection is required. | Select LM2678-3.3 only if cost sensitivity outweighs need for current limit tuning and softstart functionality. |
| TPS54560DGQ | Adjustable 3.5–60V input, 5A sync buck; 2.5V–36V output; integrated FETs; 100 kHz–2.5 MHz programmable frequency; no external boost cap needed. | Requires external feedback resistors; higher quiescent current (146 µA vs. 6 mA); different thermal profile and layout constraints. | Choose TPS54560DGQ for designs needing wider input range, higher frequency, or lower IQ in sleep mode - not a drop-in replacement. |
Compared with LM2678-3.3, LM2679SX-3.3 adds design flexibility through current limit programming and softstart; versus TPS54560DGQ, it offers simpler external component count and proven thermal performance in legacy industrial layouts, though with less configurability.
Availability
LM2679SX-3.3 is available at Aetrix Electronics and suitable for industrial automation, battery-powered test equipment, and telecom infrastructure requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2679SX-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 LM2679 series belongs to TI's SIMPLE SWITCHER® portfolio, designed specifically for engineers seeking robust, easy-to-implement DC-DC buck regulators with minimal external components and broad industrial operating ranges.
FAQ
What is the maximum continuous output current of the LM2679SX-3.3?
The LM2679SX-3.3 is rated for 5A continuous output current under specified thermal conditions (e.g., θJA ≤ 26°C/W with adequate PCB copper). Actual achievable current depends on input voltage, ambient temperature, and heatsinking. At 12VIN/3.3VOUT, typical efficiency is 82%, and thermal shutdown activates if junction temperature exceeds ~165°C. The LM2679SX-3.3 datasheet specifies 5A as the guaranteed minimum load capability across its full operating range.
Does the LM2679SX-3.3 require external feedback resistors to set the output voltage?
No. The LM2679SX-3.3 is the fixed 3.3V output variant; internal resistor dividers connect the FB pin to generate the precise 3.3V regulation point. External feedback resistors are only required for the LM2679-ADJ version. For LM2679SX-3.3, the FB pin is connected directly to the output node, and no external components are needed for voltage setting - simplifying layout and improving accuracy.
Can the LM2679SX-3.3 operate with an input voltage below 8V?
No. The LM2679SX-3.3 has a specified minimum input voltage of 8V per its Absolute Maximum and Operating Ratings. Operation below 8V may result in failure to start, unstable regulation, or undefined behavior. The internal bias circuitry and DMOS switch driver require sufficient headroom above the 3.3V output to function correctly. Attempting to operate LM2679SX-3.3 at 7V or lower violates the datasheet specifications and is not supported.
What is the purpose of the CBOOST capacitor on the LM2679SX-3.3?
The CBOOST capacitor (0.01 µF/50V ceramic) connects between the CBOOST pin and the VSW pin on the LM2679SX-3.3. It forms a bootstrap circuit that temporarily elevates the gate drive voltage above VIN, ensuring full enhancement of the internal DMOS switch and minimizing RDS(ON). This directly improves conversion efficiency - omitting or undersizing CBOOST causes increased conduction loss and potential thermal overstress. The LM2679SX-3.3 will not achieve its rated 92% efficiency without this capacitor properly installed.
Is the LM2679SX-3.3 RoHS compliant and lead-free?
Yes. The LM2679SX-3.3 is manufactured by Texas Instruments in RoHS-compliant, lead-free packaging (DDPAK-7, KTW0007B). TI's official product folder and packaging information confirm Pb-free terminations and compliance with EU RoHS Directive 2011/65/EU and JEDEC J-STD-609. All LM2679SX-3.3 units supplied by Aetrix Electronics meet current environmental compliance standards for industrial and commercial applications.
LM2679SX-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)
LM2679SX-3.3 FAQ
1.How can I place an order for LM2679SX-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679SX-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 LM2679SX-3.3 reliable?
The price and inventory of LM2679SX-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 LM2679SX-3.3 is usually 5 days.
3.What payment methods are accepted for LM2679SX-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2679SX-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679SX-3.3?
LM2679SX-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679SX-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 LM2679SX-3.3?
For technical support, including LM2679SX-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679SX-3.3 requirements.
6.How does Aetrix verify that LM2679SX-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2679SX-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 LM2679SX-3.3 meets industry standards.
7.What is the process for return or replacement of LM2679SX-3.3?
All LM2679SX-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2679SX-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 LM2679SX-3.3 part is unused and in its original packaging.
Return procedure for LM2679SX-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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