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Texas Instruments LM2678S-ADJ
- Part No.:
- LM2678S-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2678S-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:1,350
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Product details
Overview
LM2678S-ADJ from Texas Instruments is a monolithic step-down (buck) DC-DC switching regulator delivering up to 5 A output current with adjustable output voltage (1.2 V to 37 V), 260 kHz fixed-frequency operation, ±2% output tolerance, and 8 V–40 V input range. It integrates a 120 mΩ DMOS high-side switch and supports efficient system preregulation in industrial power supplies.
For engineers reviewing the LM2678S-ADJ datasheet, LM2678S-ADJ pinout, LM2678S-ADJ application, or LM2678S-ADJ equivalent, key selection criteria include its adjustable feedback architecture, ON/OFF control interface, thermal shutdown protection, and compatibility with standard off-the-shelf inductors and Schottky diodes for rapid design implementation.
Technical Context
The LM2678S-ADJ implements a fixed-frequency PWM controller with internal 260 kHz oscillator and voltage-mode feedback loop referenced to a precise 1.21 V internal bandgap reference. Its high-side DMOS switch operates with 120 mΩ RDS(ON) at 25°C, enabling >90% efficiency at full load under typical conditions.
Functional modes include active regulation (ON/OFF ≥1.4 V) and shutdown (ON/OFF ≤0.8 V), drawing only 50 µA standby current. The FB pin senses output via external resistor divider, while CB pin supplies bootstrapped gate drive to sustain MOSFET conduction during high-duty-cycle operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 5 A maximum continuous load capability with integrated thermal shutdown and current limiting. |
| Input Voltage Range | 8 V to 40 V - supports wide-range industrial and battery-derived inputs without pre-regulation. |
| Output Voltage Range | 1.2 V to 37 V - set externally via resistor divider on FB pin; enables flexible system-level voltage scaling. |
| Switching Frequency | 260 kHz ±11% - fixed internal oscillator enables predictable EMI profile and compact passive component sizing. |
| Feedback Reference | 1.21 V ±1.2% - precision internal reference ensures ±2% output tolerance over line, load, and temperature. |
| RDS(ON) | 0.12 Ω typical at 25°C - low conduction loss supports high-efficiency operation at 5 A output. |
| Standby Current | 50 µA - ultra-low quiescent draw in shutdown mode enables energy-sensitive battery applications. |
Pinout & Package
LM2678S-ADJ is available in KTW (TO-263-7), NDZ (TO-220-7), and NHM (VSON-14) packages. This entry corresponds to the TO-263-7 (KTW) variant: 10.1 mm × 15.24 mm thermally enhanced surface-mount package with exposed DAP connected to GND.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch Output | Drain node of internal high-side DMOS FET; connects to inductor and cathode of external Schottky diode - carries high dv/dt switching waveform. |
| 2 (IN) | Input Supply | Main power input (8–40 V); requires low-ESR bypass capacitor placed adjacent to minimize high-frequency noise coupling. |
| 3 (CB) | Bootstrap Capacitor | Connects to SW via 100 nF ceramic capacitor to generate gate drive voltage above IN for full FET enhancement. |
| 4 (GND) | Power Ground | Primary return path for input/output capacitors and internal circuitry; must be tied to large copper plane for thermal and EMI performance. |
| 5 (NC) | No Connect | Internally unconnected; must remain floating - no routing or soldering permitted. |
| 6 (FB) | Feedback Input | Senses output voltage via external resistor divider; regulates output by comparing to 1.21 V internal reference. |
| 7 (ON/OFF) | Enable Control | Logic-level input: ≥1.4 V enables regulation; ≤0.8 V disables output and reduces quiescent current to 50 µA. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120 mΩ DMOS Switch | Eliminates need for external high-current MOSFET and driver, reducing BOM count and layout complexity. |
| ±2% Output Tolerance | Ensures stable system rail accuracy across –40°C to +125°C junction temperature without external trimming. |
| 260 kHz Fixed-Frequency Operation | Enables consistent EMI filtering design and use of standardized, cost-effective inductor families. |
| Thermal Shutdown & Current Limit | Protects against overload and ambient overheating; automatically recovers when fault condition clears. |
| WEBENCH® Power Designer Support | Provides validated schematic, bill-of-materials, efficiency simulation, and PCB layout guidance directly from TI. |
Applications
| Industrial Power Supplies | Battery Charger Preregulator |
|---|---|
Use Scenario: 24 V industrial bus powering 5 V/3.3 V logic rails in PLC I/O modules. IC Role / Device Role / Timing Role: Primary buck converter providing regulated intermediate voltage with high efficiency and thermal robustness. Use Value: Delivers 5 A continuous output with <1.5% load regulation and built-in thermal protection for unattended operation. | Use Scenario: Li-ion battery charger using 36 V solar input to generate 12.6 V constant-voltage charge stage. IC Role / Device Role / Timing Role: Pre-regulator stepping down variable solar input before linear or switching charge controller stage. Use Value: Maintains >84% efficiency across 10–35 V input range, reducing heat dissipation in downstream charging ICs. |
| Test Equipment Power Rails | Embedded System DC-DC Conversion |
Use Scenario: Benchtop multimeter requiring clean, low-noise 15 V analog supply derived from 48 V backplane. IC Role / Device Role / Timing Role: High-PSRR buck regulator feeding precision ADC reference and op-amp bias networks. Use Value: Achieves <20 mVpp output ripple with proper output capacitor selection, meeting analog subsystem noise budgets. | Use Scenario: RISC-V-based edge gateway converting 12 V vehicle battery to 3.3 V MCU core and 1.8 V I/O rails. IC Role / Device Role / Timing Role: Main system power converter with ON/OFF control synchronized to host processor sleep/wake states. Use Value: Enables 50 µA shutdown current to extend battery runtime during deep-sleep intervals without external load switches. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596S-ADJ | 3 A output rating, 150 kHz switching frequency, higher RDS(ON) (0.22 Ω), wider VIN (4.5–40 V). | Limited to lower-power systems; less suitable for 5 A continuous loads or space-constrained layouts due to larger inductor size. | Select when cost sensitivity outweighs current requirement and thermal constraints allow derating. |
| TPS54560B | 5.5 A output, 100 V max input, adjustable frequency (100–2500 kHz), integrated soft-start, higher BOM cost. | Better suited for automotive or high-input-voltage industrial designs where 40 V input limit of LM2678S-ADJ is insufficient. | Choose for extended input range, programmable frequency, or tighter transient response in demanding environments. |
Compared with LM2596S-ADJ and TPS54560B, the LM2678S-ADJ offers optimal balance of 5 A capability, proven thermal performance in TO-263, and minimal external component count - making it ideal for cost-sensitive, high-reliability industrial buck conversion where 40 V input ceiling is acceptable.
Availability
LM2678S-ADJ is available at Aetrix Electronics and suitable for industrial power supplies, battery charger preregulators, and embedded system DC-DC conversion requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2678S-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 over 90 years of innovation history.
The LM2678S-ADJ belongs to the SIMPLE SWITCHER® family - designed specifically for ease-of-use, high-efficiency, non-isolated DC-DC conversion in industrial, test equipment, and distributed power architectures.
FAQ
What is the minimum input voltage required for stable operation of the LM2678S-ADJ?
The LM2678S-ADJ requires a minimum input voltage of 8 V to maintain regulation across its full output range. Below this threshold, the internal circuitry cannot sustain proper gate drive for the DMOS switch, resulting in dropout or shutdown. This specification is verified across –40°C to +125°C junction temperature and applies to all package variants including KTW, NDZ, and NHM.
How does the FB pin function in the LM2678S-ADJ adjustable configuration?
The FB pin on the LM2678S-ADJ senses the output voltage through an external resistor divider and compares it to an internal 1.21 V reference. For the adjustable version, the output voltage is calculated as VOUT = 1.21 V × (1 + R1/R2), where R1 connects between VOUT and FB, and R2 connects between FB and GND. This topology enables precise output setting from 1.2 V to 37 V.
Can the LM2678S-ADJ operate without the CB (bootstrap capacitor) connection?
No - the CB pin must be connected to the SW pin via a 100 nF ceramic capacitor. Without this bootstrap network, the internal high-side DMOS gate cannot be driven above the input rail, preventing full enhancement and causing excessive conduction loss, thermal runaway, or failure to start. This requirement is independent of output voltage or load condition and applies to all LM2678S-ADJ package types.
What is the maximum duty cycle supported by the LM2678S-ADJ?
The LM2678S-ADJ supports a maximum duty cycle of 91%, defined as the longest possible ON-time relative to the 260 kHz switching period. This allows operation down to VOUT/VIN ≈ 0.91 - for example, generating 37 V output from a 40 V input. Duty cycle is internally limited to prevent instability and ensure reliable gate drive timing across temperature and process variations.
Does the LM2678S-ADJ require external compensation components?
No - the LM2678S-ADJ features fully internal frequency compensation optimized for standard external component values (e.g., 10 µH inductor, 400 µF output capacitor). No external RC networks or compensation pins are needed. Stability is guaranteed when using recommended inductor ESR and capacitor values per TI's application notes and WEBENCH® design guidelines for the LM2678S-ADJ.
LM2678S-ADJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- 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:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-7)
LM2678S-ADJ FAQ
1.How can I place an order for LM2678S-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678S-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 LM2678S-ADJ reliable?
The price and inventory of LM2678S-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2678S-ADJ is usually 5 days.
3.What payment methods are accepted for LM2678S-ADJ?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678S-ADJ?
LM2678S-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678S-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 LM2678S-ADJ?
For technical support, including LM2678S-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678S-ADJ requirements.
6.How does Aetrix verify that LM2678S-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2678S-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 LM2678S-ADJ meets industry standards.
7.What is the process for return or replacement of LM2678S-ADJ?
All LM2678S-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2678S-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 LM2678S-ADJ part is unused and in its original packaging.
Return procedure for LM2678S-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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