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Texas Instruments LM2679SX-12
- Part No.:
- LM2679SX-12
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2679SX-12.pdf
- Description:
- IC REG BUCK 12V 5A TO263
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM2679SX-12 from Texas Instruments is a monolithic 5A step-down (buck) DC/DC voltage regulator with fixed 12V output, 8V–40V input range, 260 kHz fixed-frequency internal oscillator, and resistor-programmable peak current limit (3A–7A). It integrates a 120 mΩ DMOS power switch and delivers ±2% output tolerance over full line/load/temperature for industrial power supply pre-regulation.
For engineers reviewing the LM2679SX-12 datasheet, LM2679SX-12 pinout, LM2679SX-12 application, or LM2679SX-12 equivalent, key selection criteria include its 12V fixed output, thermal shutdown protection, softstart capability via external capacitor, and compatibility with standard off-the-shelf inductors and low-ESR output capacitors.
Technical Context
The LM2679SX-12 implements a voltage-mode PWM control architecture with a fixed 260 kHz oscillator, enabling predictable loop stability and simplified EMI filtering. Its internal DMOS switch operates with 120 mΩ typical RDS(ON), supporting continuous 5A output while maintaining up to 92% efficiency at 24VIN/12VOUT.
Current limiting is implemented via an external resistor (RADJ) connected to the CURRENT ADJ pin, setting peak switch current per ICL = 37,125 / RADJ (Ω), with factory-trimmed feedback reference of 1.21 V. Softstart is controlled by a linear ramp on the SOFTSTART pin using an external capacitor, preventing input surge during turn-on.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 12 V ±2% over −40°C to +125°C, 15V–40V input, 100 mA–5 A load - ensures stable rail for downstream logic or analog circuitry without external feedback resistors. |
| Input Voltage Range | 8 V to 40 V - supports wide industrial input sources including 12 V, 24 V, and 36 V nominal systems with margin for transients. |
| Switching Frequency | 260 kHz ±11% - enables use of compact, standardized inductors and simplifies EMI filter design with predictable fundamental harmonic placement. |
| Peak Switch Current Limit | Programmable 3 A to 7 A via RADJ - allows optimization of external inductor/diode ratings to match actual load fault requirements, reducing BOM cost and size. |
| Efficiency | Up to 92% at 24 VIN, 12 VOUT, 5 A - achieved via low 120 mΩ RDS(ON) DMOS switch and optimized gate drive, minimizing conduction losses in high-current paths. |
| Thermal Protection | Integrated thermal shutdown - disables switching when junction temperature exceeds safe operating limit, protecting device and system under sustained overload or poor heatsinking. |
| Quiescent Current | 6 mA typical at 12 VIN - enables low standby power consumption in always-on industrial controllers without compromising startup speed. |
Pinout & Package
LM2679SX-12 is packaged in the 7-lead DDPAK (KTW) thermally enhanced surface-mount package (Package Number KTW0007B), featuring an exposed die attach pad (DAP) that must be soldered to PCB ground plane for optimal thermal performance (θJA = 26°C/W with 7.4× DAP copper area).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW | Switch Node | Drain of internal DMOS power switch - connects to inductor input and boost capacitor; carries high di/dt switching current requiring tight layout and low-inductance routing. |
| VIN | Power Input | Main supply input (8–40 V); powers internal bias circuitry and switch - requires local 3×15 µF/50 V ceramic input capacitance placed adjacent to pin. |
| CBOOST | Bootstrap Supply | 0.01 µF capacitor between VSW and this pin - generates gate drive voltage > VIN to fully enhance internal MOSFET, minimizing RDS(ON) and conduction loss. |
| GND | Power Ground | Primary return path for switch current and IC bias - must connect directly to low-impedance ground plane; DAP (pin 9) is electrically tied to GND and requires PCB thermal pad connection. |
| CURRENT ADJ | Current Limit Set | Connects external resistor to GND - sets peak switch current via ICL = 37,125 / RADJ; 5.6 kΩ yields ~6.3 A typical limit. |
| FB | Feedback Input | Not used in LM2679SX-12 - internal resistor divider fixes output at 12 V; pin must remain unconnected per datasheet. |
| SOFTSTART | Startup Ramp Control | Accepts external capacitor to GND - linearly ramps duty cycle at power-on to limit inrush; open-circuit disables softstart. |
Key Features
| Feature | Design Value |
|---|---|
| Monolithic 5A Buck Regulator | Integrates controller, 120 mΩ DMOS switch, and protection circuitry - eliminates need for external MOSFET driver, reduces component count, and improves reliability in space-constrained designs. |
| Resistor-Programmable Current Limit | Adjusts peak switch current from 3 A to 7 A using single RADJ resistor - enables precise matching of external magnetics and diode ratings to actual application fault conditions, avoiding overdesign. |
| Softstart with External Capacitor | Linear ramp on SOFTSTART pin controls startup slew rate - prevents input surge and output overshoot during cold start into light/no-load conditions. |
| Thermal Shutdown Protection | Automatically disables switching above safe junction temperature - protects device and system during overload, ambient rise, or inadequate heatsinking without external monitoring circuitry. |
| Fixed-Frequency 260 kHz Operation | Predictable switching frequency simplifies EMI filter design and enables use of TI-recommended standard inductors - reduces design iteration time versus variable-frequency alternatives. |
Applications
| Industrial Power Pre-Regulation | High-Efficiency Battery Charging |
|---|---|
Use Scenario: Converting 24 V or 36 V industrial bus voltage to stable 12 V for powering PLC I/O modules, sensors, and communication interfaces. IC Role / Device Role / Timing Role: Primary step-down regulator delivering regulated 12 V at up to 5 A with ±2% accuracy and thermal fault protection. Use Value: Eliminates need for discrete buck controller + external MOSFET, reducing board area and improving efficiency over linear regulators (92% vs. <50% at 24 V→12 V). | Use Scenario: Providing constant-voltage stage in multi-stage Li-ion or lead-acid battery chargers powered from 28 V avionics or 36 V solar arrays. IC Role / Device Role / Timing Role: High-current pre-regulator stepping down unregulated source to 12 V before final linear or switching charge management stage. Use Value: Delivers 5 A at 92% efficiency, minimizing heat generation in enclosed charger enclosures and extending thermal headroom for continuous operation. |
| Embedded System Power Supply | Test Equipment Power Module |
Use Scenario: Generating clean 12 V rail for FPGA, microcontroller, and peripheral ICs in ruggedized edge computing gateways operating across −40°C to +85°C. IC Role / Device Role / Timing Role: Main DC/DC converter with integrated thermal shutdown and programmable current limit for robust field deployment. Use Value: ±2% output tolerance and −40°C to +125°C junction rating ensure reliable operation under wide ambient swings without derating. | Use Scenario: Powering analog front-ends and digital signal processors in portable benchtop test instruments requiring low-noise, stable 12 V from 12–40 V battery or adapter inputs. IC Role / Device Role / Timing Role: High-efficiency, low-ripple power stage with softstart to prevent measurement disturbance during instrument power-up. Use Value: Softstart-controlled turn-on suppresses output voltage overshoot, avoiding false triggering or latch-up in sensitive analog circuits during startup. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678-12 | Same pinout, identical 12 V fixed output, but lacks adjustable current limit and softstart; uses older 200 kHz oscillator. | Suitable only where programmable fault current and controlled startup are not required. | Select LM2678-12 only if legacy design reuse or lower BOM cost outweighs need for current limit tuning and softstart. |
| TPS54560B | Pin-compatible 60 V input, 5 A synchronous buck with integrated high-side/low-side FETs, 100–2500 kHz adjustable frequency, and enhanced light-load efficiency. | Better suited for wide-input, high-efficiency, or noise-sensitive applications requiring frequency agility or lower quiescent current. | Choose TPS54560B when input exceeds 40 V, synchronous rectification is needed, or programmable frequency aids EMI compliance. |
Compared with LM2678-12, LM2679SX-12 adds resistor-programmable current limit and softstart for improved system-level fault management and startup control; compared with TPS54560B, it offers simpler design with fixed frequency and proven thermal performance in DDPAK, but lacks synchronous rectification and input voltage headroom above 40 V.
Availability
LM2679SX-12 is available at Aetrix Electronics and suitable for industrial power pre-regulation, embedded system power supplies, and battery charging systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2679SX-12 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-reliability power conversion solutions.
The LM2679 series belongs to TI's SIMPLE SWITCHER® family - designed specifically for ease-of-use in non-isolated DC/DC buck applications, emphasizing minimal external components, thermal robustness, and broad industrial temperature operation.
FAQ
What is the maximum input voltage rating for the LM2679SX-12?
The absolute maximum input voltage for the LM2679SX-12 is 45 V, but the recommended operating range is 8 V to 40 V per the datasheet. Exceeding 40 V may compromise long-term reliability and thermal performance, especially under full 5 A load. The device includes internal protection against transient overvoltage, but sustained operation above 40 V is not characterized or guaranteed. Always verify input transient margins in your specific application when using LM2679SX-12.
Does the LM2679SX-12 require external feedback resistors to set the 12 V output?
No, the LM2679SX-12 has an internally trimmed resistor divider that fixes the output voltage at 12 V ±2%. The FB pin is not used and must remain unconnected - unlike the adjustable LM2679-ADJ version, which requires two external resistors. This simplifies layout and eliminates resistor tolerance errors, making LM2679SX-12 ideal for cost-sensitive, high-volume 12 V supply designs where output precision is critical.
How is the current limit programmed on the LM2679SX-12?
The current limit on the LM2679SX-12 is set by connecting a resistor (RADJ) between the CURRENT ADJ pin and GND. The peak switch current follows ICL = 37,125 / RADJ (Ω), so a 5.6 kΩ resistor yields ~6.3 A typical limit. This allows tailoring inductor and Schottky diode ratings to actual fault conditions - for example, 4.4 A limit with 8.25 kΩ - reducing BOM cost and size without sacrificing protection. LM2679SX-12 supports limits from 3 A to 7 A.
What package type does the LM2679SX-12 use, and how should the DAP be handled?
The LM2679SX-12 is offered in the 7-lead DDPAK (KTW) package (Package Number KTW0007B), which features an exposed die attach pad (DAP) on the underside. Per TI's layout guidelines, the DAP must be soldered to a dedicated PCB ground plane island with thermal vias to achieve the rated θJA = 26°C/W. Leaving the DAP unconnected degrades thermal performance significantly - θJA rises to 56°C/W - risking thermal shutdown under 5 A load. Always follow AN-1187 for copper area and via recommendations when routing LM2679SX-12.
Can the LM2679SX-12 be used with input voltages below 8 V?
No, the LM2679SX-12 is not specified or guaranteed to operate below 8 V input. The internal bias circuitry and DMOS gate drive require minimum headroom to function correctly; attempting operation below 8 V may result in erratic regulation, failure to start, or undefined behavior. For 5 V input applications, consider TI's LM2673 or LM2675 families. The 8–40 V range of LM2679SX-12 makes it suitable for 12 V, 24 V, and 36 V industrial and automotive auxiliary power systems - never for USB or low-voltage battery inputs.
LM2679SX-12 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):
- 12V
- 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-12 FAQ
1.How can I place an order for LM2679SX-12 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679SX-12 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-12 reliable?
The price and inventory of LM2679SX-12 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2679SX-12 is usually 5 days.
3.What payment methods are accepted for LM2679SX-12?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2679SX-12 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679SX-12?
LM2679SX-12 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679SX-12 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-12?
For technical support, including LM2679SX-12 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679SX-12 requirements.
6.How does Aetrix verify that LM2679SX-12 is sourced from the original manufacturer or authorized distributors?
All LM2679SX-12 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-12 meets industry standards.
7.What is the process for return or replacement of LM2679SX-12?
All LM2679SX-12 units undergo pre-shipment inspection (PSI). If there is an issue with LM2679SX-12, 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-12 part is unused and in its original packaging.
Return procedure for LM2679SX-12:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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