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Texas Instruments LM2679SDX-ADJ
- Part No.:
- LM2679SDX-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- 14-VDFN Exposed Pad
- Datasheet:
-
LM2679SDX-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A 14VSON
- Quantity:
- Payment:
- Shipping:
Inventory:1,736
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Product details
Overview
LM2679SDX-ADJ from Texas Instruments is a monolithic 5A step-down (buck) DC/DC voltage regulator with adjustable output (1.2V to 37V), 260 kHz fixed-frequency PWM control, 120 mΩ DMOS power switch, and resistor-programmable peak current limit (3A–7A). It operates from 8V to 40V input and delivers ±2% output tolerance over line/load/temperature in industrial power supplies.
For engineers reviewing the LM2679SDX-ADJ datasheet, LM2679SDX-ADJ pinout, LM2679SDX-ADJ application, or LM2679SDX-ADJ equivalent, key selection criteria include its adjustable current limit via RADJ, softstart timing capacitor interface, boost capacitor requirement for gate drive enhancement, and thermal performance in DDPAK-7 (KTW) package.
Technical Context
The LM2679SDX-ADJ implements a voltage-mode PWM controller with internal 260 kHz oscillator, feedback amplifier referenced to 1.21 V typical VFB, and current-limit protection triggered by external RADJ resistor (ICL = 37,125 / RADJ). Its DMOS switch features 0.12 Ω typical RDS(ON) at TJ = 25°C.
Operation requires external boost capacitor (0.01 µF) between SW and BOOST pins to elevate gate drive above VIN, enabling full MOSFET enhancement. Softstart is implemented via linear charging of CSS to 0.63 V threshold, controlling duty-cycle ramp-up to suppress inrush current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8V to 40V - supports wide-range unregulated DC inputs including industrial 24V and 36V rails. |
| Output Voltage Range | 1.2V to 37V - set externally via resistive divider on FB pin; enables flexible system-level rail generation. |
| Max Output Current | 5A continuous - delivered with high efficiency (up to 92%) using integrated low-RDS(ON) DMOS switch. |
| Switching Frequency | 260 kHz (±11%) - fixed internal oscillator enables predictable EMI profile and compact magnetics selection. |
| Current Limit Range | 3A to 7A - programmed via single RADJ resistor (e.g., 5.6 kΩ → 6.3 A typical), protecting external components during faults. |
| Feedback Reference | 1.21 V (±2.4%) - precise internal reference enables tight output regulation across −40°C to +125°C junction range. |
| Thermal Resistance (θJA) | 26°C/W - measured with 7.4× copper area on DDPAK-7 (KTW) package, enabling high-power operation without forced air. |
Pinout & Package
LM2679SDX-ADJ is housed in a thermally enhanced DDPAK-7 (KTW) surface-mount package with exposed die attach pad (DAP) intended for PCB ground connection to optimize thermal dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 2) | Power Input | Accepts 8V–40V unregulated DC; must be bypassed with ≥3×15 µF/50V ceramic input capacitors near pin. |
| VSW (Pin 1 & 4) | Switch Node | Drives external inductor; swings from VIN to ~−0.5V during off-time; connects to BOOST capacitor and catch diode anode. |
| BOOST (Pin 3) | Gate Drive Boost | Connects to VSW via 0.01 µF/50V ceramic capacitor to generate >VIN gate voltage for full DMOS enhancement. |
| GND (Pin 5) | Power Ground | Primary return path for switch current and IC bias; requires low-inductance connection to DAP and system ground plane. |
| CURRENT ADJ (Pin 5) | Current Limit Set | Accepts RADJ resistor to GND; sets peak switch current as ICL = 37,125 / RADJ (e.g., 5.6 kΩ → 6.3 A). |
| FB (Pin 6) | Feedback Input | Senses output voltage via resistive divider; regulates output to 1.21 V reference; high-impedance (85 nA bias). |
| SOFTSTART (Pin 7) | Startup Control | Charged by 3.7 µA internal current source to 0.63 V threshold; controls duty-cycle ramp-up time to limit inrush. |
| DAP | Thermal Pad | Exposed copper pad under package; must be soldered to large PCB ground copper area for θJA = 26°C/W performance. |
Key Features
| Feature | Design Value |
|---|---|
| Resistor-Programmable Current Limit | Enables precise fault-current tailoring (3A–7A) with single RADJ resistor, reducing inductor/diode stress and cost. |
| Integrated 120 mΩ DMOS Power Switch | Eliminates external high-side MOSFET; achieves >90% efficiency at 5A load without external driver complexity. |
| Fixed 260 kHz Oscillator | Provides stable switching frequency for predictable filter design, EMI filtering, and compatibility with standard off-the-shelf inductors. |
| Softstart with External Capacitor | Prevents input surge current via programmable startup ramp (CSS = 1 nF typical), avoiding tripped upstream supplies or blown fuses. |
| Wide Junction Temperature Range | Rated for −40°C to +125°C operation, supporting deployment in industrial motor drives, telecom rectifiers, and automotive under-hood applications. |
Applications
| Industrial Motor Drive Power Supply | Telecom Rectifier Pre-Regulator |
|---|---|
Use Scenario: Provides isolated 5V/5A auxiliary power for gate drivers and MCU logic in 48V-input servo inverters. IC Role / Device Role / Timing Role: Primary buck regulator converting 48V intermediate bus to 5V logic rail; handles transient loads up to 5A with <100 µs recovery. Use Value: Resistor-programmable current limit (6.3 A) matches motor driver short-circuit requirements while minimizing inductor size vs. fixed 7A parts. | Use Scenario: Steps down 54V telecom battery backup rail to 12V for downstream DC/DC converters in base station power systems. IC Role / Device Role / Timing Role: High-efficiency pre-regulator operating continuously at 40V input; maintains ±2% output accuracy across temperature and line variation. Use Value: 260 kHz fixed frequency simplifies EMI filter design to meet EN 55022 Class B limits without custom magnetics. |
| Battery Charger Front-End Converter | Programmable Lab Power Supply |
Use Scenario: Generates adjustable 3V–24V output for Li-ion/LiPo battery charging circuits requiring precise voltage setpoints. IC Role / Device Role / Timing Role: Adjustable-output buck controller; FB pin connected to precision DAC-controlled divider for digital voltage programming. Use Value: 1.21 V feedback reference enables <0.5% output error with 0.1% resistor tolerance, critical for constant-voltage charge phase accuracy. | Use Scenario: Serves as main output stage in benchtop power supply delivering 1.2V–30V at up to 5A with analog voltage/current control. IC Role / Device Role / Timing Role: Core regulated power stage; SOFTSTART pin driven by DAC for controlled ramp-up; CURRENT ADJ used for programmable current limiting. Use Value: DAP-connected thermal pad sustains 5A continuous output at +70°C ambient without heatsink, reducing system footprint and cost. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678SDX-5.0 | Fixed 5V output; no FB pin; identical 5A rating, 260 kHz, and DDPAK-7 package. | Not suitable for adjustable-output designs; eliminates need for external feedback divider but lacks voltage flexibility. | Select when system requires only 5V output and board space is constrained-no external resistors needed. |
| LM2596SX-ADJ | 3A rated; 150 kHz switching; TO-220-5 package; lower RDS(ON) (0.16 Ω typ); no BOOST pin required. | Limited to 3A loads; slower frequency increases inductor size; through-hole mounting complicates automated assembly. | Choose for cost-sensitive, lower-current (<3A) applications where thermal performance is less critical and through-hole is acceptable. |
Compared with LM2678SDX-5.0 and LM2596SX-ADJ, the LM2679SDX-ADJ uniquely balances 5A capability, adjustable output, and surface-mount DDPAK packaging-enabling compact, flexible, high-power designs where programmability and thermal efficiency are jointly prioritized.
Availability
LM2679SDX-ADJ is available at Aetrix Electronics and suitable for industrial motor drives, telecom rectifiers, battery chargers, and programmable lab power supplies requiring stable component supply and long-term production continuity.
Supply support for LM2679SDX-ADJ 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® family-designed specifically for ease-of-use in non-isolated DC/DC buck applications, emphasizing minimal external components, robust fault protection, and broad industrial temperature operation.
FAQ
What is the recommended boost capacitor value for LM2679SDX-ADJ?
The LM2679SDX-ADJ requires a 0.01 µF ceramic capacitor rated for ≥50V between the BOOST and VSW pins. This capacitor generates the elevated gate drive voltage needed to fully enhance the internal 120 mΩ DMOS switch, ensuring low conduction losses and >90% efficiency at 5A. Using a lower value or voltage rating risks incomplete turn-on and thermal overstress.
How do I calculate the current limit resistor (RADJ) for LM2679SDX-ADJ?
For LM2679SDX-ADJ, the peak switch current is calculated as ICL = 37,125 / RADJ (in ohms). To set a 6.3 A limit, use RADJ = 37,125 / 6.3 ≈ 5.89 kΩ - a standard 5.6 kΩ resistor yields 6.6 A typical. The LM2679SDX-ADJ datasheet specifies this relationship applies across −40°C to +125°C, with ±11% tolerance on ICL due to RADJ tolerance and internal reference drift.
Can LM2679SDX-ADJ operate with input voltage below 8V?
No - the LM2679SDX-ADJ has a minimum operating input voltage of 8V per its Absolute Maximum Ratings and Operating Ratings tables. Below 8V, the internal bias circuitry cannot sustain regulation, and the DMOS switch fails to turn on reliably. Attempting operation at 7V or lower may cause erratic switching, output dropout, or thermal shutdown. For sub-8V inputs, consider the LM2673 or LM2596 families.
What is the purpose of the DAP (Die Attach Pad) on LM2679SDX-ADJ?
The DAP on LM2679SDX-ADJ is an exposed thermal pad electrically connected to GND and thermally coupled to the die. It must be soldered to a large PCB copper area (≥1.0064 in² with 12 vias) to achieve the rated θJA = 26°C/W. Leaving the DAP unconnected degrades thermal performance by >30°C/W, risking thermal shutdown at 5A load. TI Application Note AN-1187 provides layout guidelines.
Does LM2679SDX-ADJ require an external catch diode?
Yes - LM2679SDX-ADJ requires an external Schottky diode connected from VSW to GND. The diode conducts inductor current during the switch OFF period. TI recommends a 60V-rated, 6A+ Schottky (e.g., SS36 or equivalent) with low forward voltage (<0.55V @ 5A) to minimize conduction loss and maintain >90% efficiency. No internal diode is integrated.
LM2679SDX-ADJ 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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 37V
- 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)
LM2679SDX-ADJ FAQ
1.How can I place an order for LM2679SDX-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679SDX-ADJ 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 LM2679SDX-ADJ reliable?
The price and inventory of LM2679SDX-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2679SDX-ADJ is usually 5 days.
3.What payment methods are accepted for LM2679SDX-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2679SDX-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679SDX-ADJ?
LM2679SDX-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679SDX-ADJ 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 LM2679SDX-ADJ?
For technical support, including LM2679SDX-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679SDX-ADJ requirements.
6.How does Aetrix verify that LM2679SDX-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2679SDX-ADJ 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 LM2679SDX-ADJ meets industry standards.
7.What is the process for return or replacement of LM2679SDX-ADJ?
All LM2679SDX-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2679SDX-ADJ, 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 LM2679SDX-ADJ part is unused and in its original packaging.
Return procedure for LM2679SDX-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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