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Texas Instruments LM2679SD-3.3
- Part No.:
- LM2679SD-3.3
- Manufacturer:
- Texas Instruments
- Package:
- 14-VDFN Exposed Pad
- Datasheet:
-
LM2679SD-3.3.pdf
- Description:
- IC REG BUCK 3.3V 5A 14VSON
- Quantity:
- Payment:
- Shipping:
Inventory:2,979
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Product details
Overview
LM2679SD-3.3 from Texas Instruments is a monolithic 5A step-down (buck) DC/DC voltage regulator with fixed 3.3V output, 260 kHz fixed-frequency internal oscillator, 120 mΩ DMOS power switch, and resistor-programmable current limit (3A–7A). It operates from 8V to 40V input and delivers ±2% output tolerance over full line/load/temperature range, used in industrial power supplies and embedded system pre-regulators.
For engineers reviewing the LM2679SD-3.3 datasheet, LM2679SD-3.3 pinout, LM2679SD-3.3 application, or LM2679SD-3.3 equivalent, key selection criteria include input voltage range (8–40V), output current capability (5A), thermal resistance (θJA = 26°C/W in DDPAK), softstart programmability, and adjustable peak current limit via external resistor.
Technical Context
The LM2679SD-3.3 implements a fixed-frequency PWM buck controller with internal 260 kHz oscillator and integrated 120 mΩ DMOS high-side switch. Feedback is taken directly from the output via an internal resistive divider (no external resistors required for 3.3V version), enabling stable regulation with minimal external components.
Current limiting is implemented via an external RADJ resistor connected between CURRENT ADJ pin and GND, setting peak switch current per ICL = 37,125 / RADJ (Ω). Softstart is controlled by a capacitor on the SOFTSTART pin, linearly ramping duty cycle to suppress inrush current during power-up.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±2% over −40°C to +125°C, 100mA–5A load, 8–40V input - ensures stable logic supply for microcontrollers and FPGAs. |
| Max Output Current | 5A continuous - supports high-current digital loads without external current sharing. |
| Input Voltage Range | 8V to 40V - compatible with 12V/24V industrial rails and unregulated battery-derived supplies. |
| Switching Frequency | 260 kHz (±11%) - enables use of compact off-the-shelf inductors while balancing EMI and efficiency. |
| Efficiency | Up to 92% (typ. 82% at 12VIN/5A) - reduces thermal load and improves system power density. |
| Thermal Resistance | θJA = 26°C/W (DDPAK package, 7.4× copper area) - enables 5A operation without external heatsink under typical PCB layout. |
| Current Limit Range | 3A to 7A (programmable via RADJ) - allows optimization of external inductor/diode ratings for cost and size. |
Pinout & Package
LM2679SD-3.3 is packaged in a 7-pin DDPAK (Package Number KTW0007B), thermally enhanced surface-mount package with exposed die attach pad (DAP) that must be soldered to PCB ground plane for optimal thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW | Switch Node | Drives external inductor; swings from VIN to ~−0.5V (Schottky drop); requires low-inductance routing. |
| VIN | Power Input | Supplies internal circuitry and switch; requires local 3×15μF/50V ceramic+electrolytic bypass near pin. |
| CBOOST | Bootstrap Capacitor | 0.01μF/50V ceramic from pin 3 to VSW - enables full gate drive for low RDS(on) operation. |
| GND | Power Ground | Common return for switch, feedback, and bias; must connect to low-impedance ground plane. |
| CURRENT ADJ | Current Limit Set | Connects to GND via RADJ (e.g., 5.6kΩ → 6.3A limit); sets peak switch current before foldback. |
| FB | Feedback Input | Internally tied to 3.3V divider - direct connection to output required; no external resistors needed. |
| SOFTSTART | Startup Control | Capacitor to GND (e.g., 1nF → ~10ms ramp) - controls duty-cycle rise time to limit inrush. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120 mΩ DMOS switch | Eliminates need for external high-side MOSFET and driver, reducing BOM count and layout complexity. |
| Resistor-programmable current limit | Enables precise fault-current tailoring (3–7A) to match inductor saturation and diode ratings, avoiding overdesign. |
| 260 kHz fixed-frequency operation | Provides predictable EMI profile and simplifies filter design versus variable-frequency alternatives. |
| Softstart with external capacitor | Prevents input surge and output overshoot during power-on, critical for systems with sensitive downstream ICs. |
| −40°C to +125°C junction range | Supports operation in harsh industrial and automotive under-hood environments without derating. |
Applications
| Industrial PLC Power Supply | Embedded System Pre-Regulator |
|---|---|
Use Scenario: Provides clean 3.3V rail for ARM Cortex-M7 microcontroller, Ethernet PHY, and CAN transceiver in a DIN-rail mounted controller. IC Role / Device Role / Timing Role: Primary buck regulator delivering regulated 3.3V at up to 5A; handles wide 12–36V DC input from factory power bus. Use Value: Fixed 3.3V output eliminates feedback resistor errors; ±2% tolerance ensures reliable logic-level compliance across temperature. | Use Scenario: Generates 3.3V from 24V intermediate bus to power FPGA configuration memory and I/O banks in edge AI gateway. IC Role / Device Role / Timing Role: High-current pre-regulator stepping down 24V to 3.3V before LDO post-regulation; operates in continuous conduction mode. Use Value: 92% peak efficiency minimizes heat in sealed enclosure; DAP-connected DDPAK package enables conduction cooling through PCB. |
| Battery Charger Auxiliary Rail | Test Equipment Power Module |
Use Scenario: Supplies 3.3V to MCU, display, and sensor interface in 24V-input lithium-ion battery charger with active balancing. IC Role / Device Role / Timing Role: Secondary regulator powered from main 24V charging bus; includes softstart to avoid triggering input overcurrent protection during plug-in. Use Value: Programmable current limit (via 5.6kΩ RADJ) restricts fault current to 6.3A, protecting charger's primary stage during short-circuit events. | Use Scenario: Powers analog front-end and ADC reference in portable bench multimeter with 12–32V universal AC/DC adapter input. IC Role / Device Role / Timing Role: Main 3.3V supply for precision analog circuitry; uses low-noise layout with separate ground plane and feedforward capacitor. Use Value: 260 kHz switching frequency avoids interference with 50/60 Hz mains harmonics and 1 MHz+ signal acquisition bands. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678SD-3.3 | Same pinout, 65 kHz switching frequency, lower efficiency (85% typ.), higher RDS(on) (200 mΩ). | Lower EMI but larger magnetics; less suitable for space-constrained designs requiring high power density. | Choose when EMI filtering priority outweighs size/efficiency; verify thermal margin at 5A with θJA = 35°C/W. |
| TPS54560QDGQRQ1 | Automotive-grade (AEC-Q100), 60V max input, 500 kHz sync capability, integrated compensation. | Supports wider input (6–60V) and vehicle battery transients; adds enable, power-good, and thermal shutdown flags. | Choose for automotive or high-reliability industrial use where extended input range and diagnostics are required. |
Compared with LM2678SD-3.3, the LM2679SD-3.3 delivers higher efficiency and smaller magnetics due to 260 kHz operation; compared with TPS54560QDGQRQ1, it lacks automotive qualification and diagnostic features but offers lower system cost and simpler layout for non-automotive 8–40V applications.
Availability
LM2679SD-3.3 is available at Aetrix Electronics and suitable for industrial PLCs, embedded pre-regulators, battery charger auxiliary rails, and test equipment power modules requiring stable component supply and long-term manufacturability.
Supply support for LM2679SD-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-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, minimizing external component count while maintaining robust performance across industrial temperature ranges.
FAQ
What is the maximum input voltage rating for the LM2679SD-3.3?
The absolute maximum input voltage for the LM2679SD-3.3 is 45V, but the recommended operating range is 8V to 40V. Exceeding 40V may trigger internal protection or reduce reliability. The device is commonly used with 12V, 24V, or 36V industrial DC buses, and its 40V upper limit accommodates transient spikes in such systems. Always ensure input capacitors are rated ≥1.3× maximum expected input voltage.
Does the LM2679SD-3.3 require external feedback resistors?
No, the LM2679SD-3.3 does not require external feedback resistors. It is the fixed 3.3V output variant, with internal resistor divider network connecting the FB pin to the regulated output. Only the LM2679-ADJ version requires two external resistors to set the output voltage. For LM2679SD-3.3, the FB pin must be connected directly to the output node to close the control loop.
How is the current limit programmed on the LM2679SD-3.3?
The current limit on the LM2679SD-3.3 is programmed using an external resistor (RADJ) connected between the CURRENT ADJ pin and GND. The peak switch current follows ICL = 37,125 / RADJ (Ω), yielding 6.3A with a 5.6 kΩ resistor. This feature allows designers to match the current limit precisely to their inductor saturation current and diode ratings, avoiding over-specification. Values below 3A are not recommended per datasheet guidance.
What package type is used for the LM2679SD-3.3, and how should the DAP be handled?
The LM2679SD-3.3 uses the 7-pin DDPAK package (TI package code KTW0007B), which includes an exposed Die Attach Pad (DAP). The DAP must be soldered to a dedicated PCB ground plane or thermal pad using multiple vias to achieve the specified θJA = 26°C/W. Leaving the DAP unconnected degrades thermal performance significantly - θJA rises to 56°C/W - and risks thermal shutdown under 5A load.
Can the LM2679SD-3.3 operate without a softstart capacitor?
Yes, the LM2679SD-3.3 can operate without a softstart capacitor: the SOFTSTART pin may be left open-circuited if gradual turn-on is not required. However, omitting the capacitor increases inrush current during power application, potentially tripping upstream current limits or causing output overshoot into light/no-load conditions. For robust system startup - especially with large output capacitance or sensitive downstream ICs - a 1 nF capacitor is commonly used to achieve ~10 ms softstart time.
LM2679SD-3.3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- 14-VDFN Exposed Pad
- 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:
- 14-VSON (5x6)
LM2679SD-3.3 FAQ
1.How can I place an order for LM2679SD-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679SD-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 LM2679SD-3.3 reliable?
The price and inventory of LM2679SD-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 LM2679SD-3.3 is usually 5 days.
3.What payment methods are accepted for LM2679SD-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2679SD-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679SD-3.3?
LM2679SD-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679SD-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 LM2679SD-3.3?
For technical support, including LM2679SD-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679SD-3.3 requirements.
6.How does Aetrix verify that LM2679SD-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2679SD-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 LM2679SD-3.3 meets industry standards.
7.What is the process for return or replacement of LM2679SD-3.3?
All LM2679SD-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2679SD-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 LM2679SD-3.3 part is unused and in its original packaging.
Return procedure for LM2679SD-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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