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Texas Instruments LM2679T-ADJ
- Part No.:
- LM2679T-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- TO-220-7 Formed Leads
- Datasheet:
-
LM2679T-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A TO220-7
- Quantity:
- Payment:
- Shipping:
Inventory:4,670
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Product details
Overview
LM2679T-ADJ from Texas Instruments is a monolithic 5A step-down (buck) DC/DC switching regulator with adjustable output voltage (1.2V to 37V), 260 kHz fixed-frequency internal oscillator, and resistor-programmable peak current limit (3A–7A). It integrates a 120 mΩ DMOS power switch and supports softstart via external capacitor. It is used in high-efficiency pre-regulators for industrial power systems requiring stable 5A output under 8V–40V input.
For engineers reviewing the LM2679T-ADJ datasheet, LM2679T-ADJ pinout, LM2679T-ADJ application, or LM2679T-ADJ equivalent, key selection criteria include its adjustable feedback threshold (1.21 V), programmable current limit via RADJ, thermal shutdown protection, ±2% output tolerance over full line/load, and compatibility with standard off-the-shelf inductors and low-ESR output capacitors.
Technical Context
The LM2679T-ADJ implements a voltage-mode PWM controller with a fixed 260 kHz oscillator and internal gate driver optimized for driving its integrated 120 mΩ DMOS switch. Feedback is taken from an external resistor divider connected to the FB pin, referenced to a precise 1.21 V internal bandgap.
Current limiting is achieved by sensing the switch current through an internal sense circuit and comparing it to a voltage derived from RADJ (ICL = 37,125 / RADJ Ω). Softstart is implemented via linear ramping of the internal error amplifier reference using a capacitor on the SS pin, with a typical 3.7 µA charging current and 0.63 V threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 5 A continuous - supports high-power loads without external current-sharing or heatsink dependency beyond package thermal limits |
| Input Voltage Range | 8 V to 40 V - enables direct operation from unregulated industrial rails, telecom -48 V derived supplies, or automotive battery systems |
| Output Voltage Range | 1.2 V to 37 V (adjustable) - set via external resistor divider on FB pin; allows flexible system-level voltage scaling |
| Feedback Reference | 1.21 V ±1.2% - defines output accuracy baseline; determines VOUT = 1.21 × (1 + R1/R2) for stable regulation |
| Switch On-Resistance | 0.12 Ω typical - minimizes conduction loss at 5 A, enabling >92% efficiency at optimal VIN/VOUT ratios |
| Oscillator Frequency | 260 kHz ±11% - fixes minimum external component size; compatible with standard off-the-shelf 10–47 µH buck inductors |
| Current Limit Range | 3 A to 7 A - programmed via RADJ (e.g., 5.6 kΩ → 6.3 A); protects inductor/diode during overload without oversized components |
| Junction Temp Range | −40°C to +125°C - qualified for industrial and extended-temperature embedded applications with no derating below 125°C |
Pinout & Package
LM2679T-ADJ is available in TO-220 (NDZ0007B) and DDPAK (KTW0007B) packages. The TO-220 variant uses 7 leads with exposed tab for thermal dissipation; the DDPAK offers lower θJA (26°C/W with 7.4× copper area) and surface-mount compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 2) | Power Input | Accepts 8–40 V supply; must be bypassed with ≥3×15 µF/50 V ceramic or low-ESR electrolytic near pin |
| VSW (Pin 1 & 4) | Switch Node | Drives external catch diode and inductor; swings from VIN to ~−0.5 V; requires low-inductance layout |
| GND (Pin 3) | Power Ground | Reference for all internal circuits and switch return; requires low-impedance ground plane |
| CURRENT ADJ (Pin 5) | Current Limit Set | Connects to ground via RADJ; sets ICL = 37,125 / RADJ (e.g., 5.6 kΩ → 6.3 A) |
| FB (Pin 6) | Feedback Input | High-impedance (85 nA bias) node; connects to resistor divider to program output voltage |
| SOFTSTART (Pin 7) | Startup Control | Charged by 3.7 µA internal current source; 0.63 V threshold initiates full regulation; open for no softstart |
| BOOST (Pin 8) | Gate Drive Boost | Connects to VSW via 0.01 µF/50 V ceramic; lifts gate drive above VIN for full MOSFET enhancement |
Key Features
| Feature | Design Value |
|---|---|
| Resistor-Programmable Current Limit | Enables precise fault-current tailoring (3–7 A) without redesigning magnetics or diodes; reduces BOM cost and board space |
| Integrated 120 mΩ DMOS Switch | Eliminates need for external high-side MOSFET and driver; simplifies layout and improves reliability vs discrete solutions |
| 260 kHz Fixed-Frequency Operation | Ensures predictable EMI profile and enables use of standardized, low-cost inductors from Renco, Pulse, Coilcraft |
| Softstart with External Capacitor | Prevents input surge current at turn-on; eliminates need for sequenced enable logic or external timers |
| Thermal Shutdown Protection | Internally disables switch above safe junction temperature; prevents catastrophic failure during sustained overload or poor heatsinking |
| ±2% Output Tolerance | Maintains tight regulation across −40°C to +125°C and full load range; reduces need for post-regulation LDOs |
Applications
| Industrial Power Pre-Regulator | Battery Charger Front-End |
|---|---|
Use Scenario: Converts 24 V or 36 V unregulated industrial bus to 5 V or 12 V intermediate rail for downstream converters. IC Role / Device Role / Timing Role: Primary step-down regulator delivering up to 5 A with high efficiency and thermal robustness. Use Value: Replaces linear pre-regulators, reducing heat generation by >75%; supports wide input transients common in factory automation systems. | Use Scenario: Provides constant-current/constant-voltage stage for Li-ion or lead-acid battery chargers operating from 12–40 V sources. IC Role / Device Role / Timing Role: Adjustable-output buck controller regulating charge voltage and limiting peak current via RADJ. Use Value: Enables single-chip CC/CV control without microcontroller; programmable current limit avoids over-sizing diodes and inductors for nominal 3–4 A charge profiles. |
| Telecom System Supply | Embedded Computing Power |
Use Scenario: Generates 3.3 V or 5 V from −48 V telecom rectified bus (via isolated front-end) for base station control cards. IC Role / Device Role / Timing Role: High-input-voltage buck converter accepting 8–40 V after isolation; handles wide line variation and transient surges. Use Value: Delivers 5 A at >90% efficiency with minimal heatsink; meets stringent telecom reliability and thermal cycling requirements. | Use Scenario: Powers FPGA, SoC, or DSP subsystems in ruggedized edge computing devices with ambient temperatures up to 85°C. IC Role / Device Role / Timing Role: Main point-of-load regulator with softstart to prevent brownout during cold boot and thermal shutdown for long-term reliability. Use Value: Eliminates need for external current-sense amplifiers or thermal sensors; simplifies compliance with IEC 60950 creepage/clearance via integrated switch. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678-5.0 | Fixed 5 V output; identical pinout, package, and 5 A rating; no FB or RADJ pins | Not suitable for adjustable-output designs; eliminates resistor divider but removes voltage flexibility | Select when system requires only 5 V and simplified layout is prioritized over programmability |
| LM2596-ADJ | 3 A rated; 150 kHz oscillator; higher RDS(ON) (0.16 Ω); different pinout and package (TO-220-5) | Limited to 3 A loads; requires larger inductor for same ripple; less efficient at 5 A | Choose only for cost-sensitive, lower-current (<3 A) applications where footprint compatibility is not required |
Compared with LM2678-5.0 and LM2596-ADJ, the LM2679T-ADJ uniquely combines 5 A capability, adjustable output, and resistor-programmable current limit in a single TO-220/DDPAK package-enabling compact, thermally robust, and design-flexible buck regulation where output voltage or fault-current thresholds may vary across product variants.
Availability
LM2679T-ADJ is available at Aetrix Electronics and suitable for industrial power pre-regulators, battery charger front-ends, and telecom system supplies requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.
Supply support for LM2679T-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 ICs, with decades of expertise in high-reliability power conversion solutions.
The LM2679 series belongs to TI's SIMPLE SWITCHER® family-designed specifically for engineers needing fast, reliable, and minimal-component buck regulator designs without sacrificing performance or thermal safety.
FAQ
What is the maximum output voltage that can be set using the LM2679T-ADJ?
The LM2679T-ADJ supports an adjustable output voltage range of 1.2 V to 37 V, determined by the external resistor divider on the FB pin and the internal 1.21 V reference. This range is validated across the full operating temperature and load conditions specified in the datasheet, with output tolerance held to ±2% at the extremes.
How do I calculate the current limit resistor (RADJ) for a desired peak switch current?
For the LM2679T-ADJ, the peak switch current ICL is calculated as ICL = 37,125 / RADJ (in ohms). To achieve a 5.5 A limit, RADJ = 37,125 / 5.5 ≈ 6.75 kΩ. The datasheet confirms this relationship applies across the full 3 A to 7 A range and is independent of input/output voltage.
Can the LM2679T-ADJ operate without a softstart capacitor?
Yes-the LM2679T-ADJ operates without a softstart capacitor. Pin 7 (SOFTSTART) may be left open-circuited for immediate startup. However, omitting the capacitor increases inrush current and may cause input voltage sag or output overshoot under light-load conditions, especially at high VIN/VOUT ratios.
What is the purpose of the BOOST capacitor, and what value is recommended for the LM2679T-ADJ?
The BOOST capacitor (0.01 µF/50 V ceramic) connects between the BOOST pin (Pin 8) and VSW (Pin 1) to generate a gate-drive voltage above VIN, ensuring full enhancement of the internal DMOS switch. This reduces RDS(ON) and improves efficiency-TI specifies this exact value across all operating conditions in the LM2679T-ADJ datasheet.
Does the LM2679T-ADJ require an external catch diode, and what specifications are critical?
Yes-the LM2679T-ADJ requires an external Schottky catch diode connected from VSW to GND. Critical specs include: reverse voltage rating ≥1.3×VIN(max), forward current rating ≥5 A, and low forward voltage (≤0.5 V at 5 A) to minimize conduction loss and maintain >90% efficiency. TI recommends 6TQ045S in typical 5 A designs.
LM2679T-ADJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-220-7 Formed Leads
- Packaging:
- Tube
- 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:
- Through Hole
- Supplier Device Package:
- TO-220-7
LM2679T-ADJ FAQ
1.How can I place an order for LM2679T-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2679T-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 LM2679T-ADJ reliable?
The price and inventory of LM2679T-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2679T-ADJ is usually 5 days.
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2679T-ADJ?
LM2679T-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2679T-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 LM2679T-ADJ?
For technical support, including LM2679T-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2679T-ADJ requirements.
6.How does Aetrix verify that LM2679T-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2679T-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 LM2679T-ADJ meets industry standards.
7.What is the process for return or replacement of LM2679T-ADJ?
All LM2679T-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2679T-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 LM2679T-ADJ part is unused and in its original packaging.
Return procedure for LM2679T-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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