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Texas Instruments LM2679SX-ADJ
- Part No.:
- LM2679SX-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2679SX-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:4,490
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Product details
Overview
LM2679SX-ADJ from Texas Instruments is a monolithic 5-A step-down (buck) DC/DC regulator with adjustable output (1.2 V to 37 V), 260-kHz fixed-frequency PWM control, 120-mΩ DMOS high-side switch, and resistor-programmable current limit (5.5–7.6 A at 5.6 kΩ). It operates from 8 V to 40 V input and delivers ±2% output voltage accuracy over line, load, and temperature - used in industrial power supplies and battery chargers.
For engineers reviewing the LM2679SX-ADJ datasheet, LM2679SX-ADJ pinout, LM2679SX-ADJ application, or LM2679SX-ADJ equivalent, key selection criteria include its adjustable feedback architecture, soft-start timing capacitor interface, bootstrapped gate drive for high-side FET, and thermal shutdown with programmable overcurrent protection.
Technical Context
The LM2679SX-ADJ implements a voltage-mode PWM controller with internal 260-kHz oscillator, driving an integrated 120-mΩ DMOS high-side switch. Its feedback loop senses output voltage via external resistor divider connected to FB pin, referenced to 1.21 V typical VFB. Current limiting is set by RADJ resistor tied to Current_adjust pin, establishing ICL = 37,125 / RADJ.
Soft-start is implemented via external capacitor on SS pin, controlling duty-cycle ramp-up; CB pin connects to a 0.01 µF bootstrap capacitor across SW and VSW to ensure full gate drive. The device supports continuous conduction mode operation with up to 91% maximum duty cycle and requires low-ESR input/output capacitors and a coupled inductor for stable regulation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output current | 5 A continuous - supports high-power loads without external pass devices |
| Input voltage range | 8 V to 40 V - compatible with 12 V/24 V industrial rails and wide-range battery inputs |
| Output voltage range | 1.2 V to 37 V adjustable - configured via external resistor divider on FB pin |
| Switch ON-resistance | 0.14 Ω max at 25°C - minimizes conduction loss and enables >92% peak efficiency |
| Oscillator frequency | 260 kHz ±11% - enables use of compact off-the-shelf inductors and reduces EMI filtering burden |
| Feedback reference voltage | 1.21 V ±1.2% - sets output accuracy and defines resistor-divider ratio for VOUT |
| Current limit range | 3 A to 7 A programmable - set by single RADJ resistor (e.g., 5.6 kΩ yields 5.5–7.6 A) |
| Operating junction temp | −40°C to +125°C - qualified for harsh industrial and automotive under-hood environments |
Pinout & Package
LM2679SX-ADJ is packaged in TO-263 (KTW) - 7-pin surface-mount package with exposed thermal pad (10.10 mm × 8.89 mm), optimized for high-current thermal dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch output | Drain node of internal DMOS FET; connects to inductor and Schottky diode cathode - switching node with fast dv/dt |
| 2 (VIN) | Input supply | Main power input (8–40 V); must be bypassed with low-ESR capacitors placed adjacent to pin |
| 3 (CB) | Bootstrap capacitor | Connects 0.01 µF capacitor to SW pin to generate gate drive voltage > VIN for full FET enhancement |
| 4 (GND) | Power ground | Common return for input/output capacitors and thermal pad; requires low-inductance PCB plane |
| 5 (IADJ) | Current adjust | Inputs bias current (1.21 V / RADJ) to set peak switch current limit per ICL = 37,125 / RADJ |
| 6 (FB) | Feedback sense | High-impedance input (85 nA bias) referenced to 1.21 V; connects to resistor divider for adjustable VOUT |
| 7 (SS) | Soft-start | Accepts external capacitor to linearly ramp duty cycle at startup; floating disables soft-start |
Key Features
| Feature | Design Value |
|---|---|
| Resistor-programmable current limit | Enables precise overcurrent protection tuning (3–7 A) without external sensing resistors or ICs |
| Integrated 120-mΩ DMOS switch | Eliminates need for external MOSFET and driver; reduces BOM count and layout complexity |
| 260-kHz fixed-frequency operation | Ensures predictable EMI spectrum and simplifies filter design versus variable-frequency alternatives |
| ±2% output voltage tolerance | Maintains tight regulation across full line/load/temperature - critical for sensitive downstream circuitry |
| Thermal shutdown protection | Automatically disables switching above safe junction temperature - prevents damage during overload or poor heatsinking |
| Soft-start with external capacitor | Controls inrush current during power-up; avoids input rail sag and prevents false triggering of upstream protection |
Applications
| Industrial Power Supply | Battery Charger |
|---|---|
Use Scenario: 24 V input converted to 15 V @ 4 A for PLC I/O modules with transient-heavy loads. IC Role / Device Role / Timing Role: Primary buck regulator providing regulated DC bus; handles 100 ms load steps up to 4 A with <150 mV undershoot. Use Value: Programmable current limit protects against short-circuit faults while maintaining 91% efficiency at full load. |
Use Scenario: 36 V lead-acid battery charger with constant-voltage/constant-current profile for 12 V SLA batteries. IC Role / Device Role / Timing Role: Adjustable-output buck stage delivering 13.8 V at up to 5 A; soft-start prevents surge into depleted battery. Use Value: 1.21 V precision feedback reference enables ±0.15 V CV accuracy; thermal shutdown prevents overheating during CC phase. |
| Motor Drive Pre-regulator | Test Equipment Power Module |
Use Scenario: 40 V unregulated rail stepped down to 5 V @ 3 A for gate drivers and logic in a 3-phase inverter. IC Role / Device Role / Timing Role: High-efficiency preregulator supplying isolated DC/DC converters; withstands 40 V transients per spec. Use Value: 8–40 V input range accommodates motor back-EMF spikes; 125°C max junction rating supports compact enclosure mounting. |
Use Scenario: Bench power supply module with user-adjustable 1.2–30 V output and digital current monitoring. IC Role / Device Role / Timing Role: Core adjustable buck regulator; FB pin interfaced to DAC-controlled resistor divider for programmable VOUT. Use Value: Resistor-programmable current limit allows safe current limiting independent of output voltage setting. |
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-ADJ | Lower 3-A output rating; same 260-kHz frequency and adjustable output, but no programmable current limit | Suitable only for ≤3 A loads; lacks ICL adjustment - requires external current-sense circuitry for overcurrent protection | Select when cost sensitivity outweighs current limit flexibility and 5-A capability is unnecessary |
| TPS54560B | Higher 60-V input rating, 500-kHz switching, and integrated compensation; uses current-mode control instead of voltage-mode | Better suited for high-input-voltage designs (e.g., 48 V telecom); faster transient response but requires different loop compensation | Prefer when input exceeds 40 V or when higher switching frequency enables smaller magnetics |
Compared with LM2678SD-ADJ, LM2679SX-ADJ delivers 67% higher current capacity and built-in programmable overcurrent protection; compared with TPS54560B, it offers simpler voltage-mode design and lower EMI at the expense of input voltage headroom and loop bandwidth.
Availability
LM2679SX-ADJ is available at Aetrix Electronics and suitable for industrial power supplies, battery charging systems, and motor drive pre-regulators requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LM2679SX-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 company designing analog and embedded processing solutions, with leadership in power management ICs and broad technical support infrastructure.
The LM2679 series belongs to TI's SIMPLE SWITCHER® family - engineered for ease of use in high-efficiency, medium-power DC/DC conversion where minimal external components and proven reliability are prioritized over ultra-high density or digital control.
FAQ
What is the recommended input capacitor configuration for LM2679SX-ADJ?
The LM2679SX-ADJ requires three 15 µF/50 V ceramic capacitors placed as close as possible to the VIN and GND pins to minimize high-frequency switching noise and input ripple. Total effective capacitance should exceed 45 µF with low ESR (<10 mΩ), and RMS current rating must support ≥2.5 A. TI recommends X7R dielectric types with 1206 or larger case sizes for thermal stability.
How do I calculate the current limit resistor (RADJ) for a 6-A trip point on LM2679SX-ADJ?
For LM2679SX-ADJ, the peak switch current limit is calculated as ICL = 37,125 / RADJ (in ohms). To achieve a nominal 6-A limit, solve RADJ = 37,125 / 6 ≈ 6.19 kΩ - use a standard 6.2 kΩ ±1% metal-film resistor. At −40°C to +125°C, this yields a guaranteed range of 5.3 A to 8.1 A per datasheet specifications.
Can LM2679SX-ADJ operate in discontinuous conduction mode (DCM)?
Yes, LM2679SX-ADJ automatically transitions into discontinuous conduction mode at light loads (typically <10% of full scale). Its voltage-mode control architecture maintains regulation across both CCM and DCM, with no external mode-setting required. Output ripple increases slightly in DCM, but stability is preserved due to internal compensation optimized for the 260-kHz fixed frequency.
What is the minimum output capacitor ESR needed for stable operation of LM2679SX-ADJ?
LM2679SX-ADJ does not specify a minimum ESR - unlike older current-mode controllers, its internal voltage-mode compensation is designed to remain stable with low-ESR ceramics (e.g., <5 mΩ). However, TI recommends ≥220 µF total output capacitance with ≤15 mΩ ESR to meet 1% output ripple targets and maintain unity-gain bandwidth below 40 kHz per application guidelines.
Is the thermal pad of the TO-263 package for LM2679SX-ADJ electrically connected?
Yes, the exposed thermal pad on the LM2679SX-ADJ TO-263 (KTW) package is internally connected to GND. It must be soldered to a dedicated PCB copper pour tied directly to the main ground plane using ≥4 thermal vias (0.3 mm diameter) to achieve optimal thermal performance. Failure to connect the pad degrades RθJA from 26°C/W to >56°C/W, risking thermal shutdown under full load.
LM2679SX-ADJ 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:
- 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:
- TO-263 (DDPAK-7)
LM2679SX-ADJ FAQ
1.How can I place an order for LM2679SX-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679SX-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 LM2679SX-ADJ reliable?
The price and inventory of LM2679SX-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2679SX-ADJ is usually 5 days.
3.What payment methods are accepted for LM2679SX-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2679SX-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679SX-ADJ?
LM2679SX-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679SX-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 LM2679SX-ADJ?
For technical support, including LM2679SX-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679SX-ADJ requirements.
6.How does Aetrix verify that LM2679SX-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2679SX-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 LM2679SX-ADJ meets industry standards.
7.What is the process for return or replacement of LM2679SX-ADJ?
All LM2679SX-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2679SX-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 LM2679SX-ADJ part is unused and in its original packaging.
Return procedure for LM2679SX-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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