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Texas Instruments LM2678SX-ADJ
- Part No.:
- LM2678SX-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2678SX-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:2,476
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Product details
Overview
LM2678SX-ADJ from Texas Instruments is a monolithic step-down (buck) DC-DC switching regulator IC with integrated 120 mΩ DMOS high-side power switch, delivering up to 5 A output current, adjustable output voltage from 1.2 V to 37 V, and 8 V–40 V input range - used in high-efficiency industrial power supplies and battery-based systems.
For engineers reviewing the LM2678SX-ADJ datasheet, LM2678SX-ADJ pinout, LM2678SX-ADJ application, or LM2678SX-ADJ equivalent, key selection criteria include its 260 kHz fixed-frequency oscillator, ±2% output voltage tolerance over line/load/temperature, 50 µA standby current in shutdown mode, thermal shutdown and current limiting, and TO-263-7 (KTW) package compatibility with standard off-the-shelf inductors.
Technical Context
The LM2678SX-ADJ implements a voltage-mode PWM controller with a fixed 260 kHz internal oscillator and internal high-side DMOS FET switch. Its feedback loop uses a precision 1.21 V reference (VFB) sensed at the FB pin, enabling accurate output regulation via external resistor divider for the adjustable version.
It operates in continuous conduction mode (CCM) across full load range and supports active control via ON/OFF pin (1.4 V threshold), with built-in cycle-by-cycle current limiting (6.1–8.3 A), thermal shutdown, and bootstrap-driven gate drive (CB pin connected to SW). Input-to-output isolation is maintained by the external catch diode and inductor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output current | 5 A maximum 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) - set precisely via external R1/R2 divider on FB pin. |
| Feedback voltage | 1.21 V ±1.2% (TJ = –40°C to 125°C) - determines output accuracy and stability margin. |
| Switching frequency | 260 kHz ±11% - enables use of compact magnetics and predictable EMI filtering. |
| RDS(ON) | 0.12 Ω typical at TJ = 25°C - minimizes conduction loss and improves efficiency >90% at full load. |
| Standby current | 50 µA max at TJ = 25°C - enables low-power system sleep modes without auxiliary LDOs. |
Pinout & Package
LM2678SX-ADJ is supplied in the KTW (TO-263-7) thermally enhanced surface-mount package (10.1 mm × 15.24 mm), with exposed DAP tied to GND for optimal thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch output | Drain node of internal high-side DMOS FET - connects directly to inductor and cathode of external Schottky diode; switches between VIN and ~–0.5 V. |
| 2 (VIN) | Input supply | Main power input (8–40 V); must be bypassed with low-ESR capacitor placed adjacent to pin for stable operation. |
| 3 (CB) | Bootstrap capacitor | Connects to SW via 100 nF ceramic capacitor - provides gate drive voltage >VIN to fully enhance internal FET. |
| 4 (GND) | Power ground | Primary return path for input/output capacitors and internal circuitry; requires low-inductance connection to PCB ground plane. |
| 5 (NC) | No connect | Internally unconnected - must remain floating; no routing or soldering required. |
| 6 (FB) | Feedback sense | High-impedance input (85 nA bias) monitoring output voltage divider - sets regulated VOUT = 1.21 V × (1 + R1/R2). |
| 7 (ON/OFF) | Enable control | Logic-level input: <0.8 V = shutdown (50 µA IQ), >1.4 V = active; internal 20 µA pull-up allows open-circuit enable. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120 mΩ DMOS switch | Eliminates need for external MOSFET and driver, reducing BOM count and layout complexity while maintaining >90% efficiency at 5 A. |
| Fixed 260 kHz oscillator | Enables consistent EMI profile and simplifies filter design; avoids frequency jitter issues common in variable-frequency controllers. |
| ±2% output tolerance | Guarantees tight regulation across full temperature and load range without trimming - critical for sensitive analog or digital loads. |
| Thermal shutdown & current limit | Protects device under overload or poor heatsinking; cycle-by-cycle current limit (6.1–8.3 A) prevents inductor saturation and catastrophic failure. |
| 50 µA shutdown quiescent current | Supports battery-powered applications requiring multi-day standby - e.g., remote sensors or backup power systems. |
Applications
| Industrial Power Supply | Battery-Based System |
|---|---|
Use Scenario: 24 V bus converted to 5 V/3.3 V for PLC I/O modules and fieldbus interfaces. IC Role / Device Role / Timing Role: Primary buck regulator providing isolated, high-current, low-noise DC rail with fast transient response. Use Value: Delivers 5 A at >90% efficiency with minimal thermal rise on standard 2-layer PCBs using TO-263 thermal pad. | Use Scenario: 12 V sealed lead-acid or LiFePO4 battery powering embedded telemetry unit with deep-sleep cycles. IC Role / Device Role / Timing Role: Main system regulator with ON/OFF pin controlled by microcontroller to enter ultra-low-power state. Use Value: Reduces system standby consumption to <100 µA total, extending battery life beyond 6 months in intermittent transmit mode. |
| Automotive Pre-regulator | Test Equipment Power |
Use Scenario: Vehicle 12 V/24 V battery feeding linear regulators for precision analog front-ends in diagnostic tools. IC Role / Device Role / Timing Role: High-efficiency preregulator stepping down to 8 V before LDOs - minimizing heat dissipation and dropout stress. Use Value: Maintains stable 8 V output across cold-crank (6 V) to load-dump (40 V) transients, eliminating need for oversized input capacitors. | Use Scenario: Benchtop power supply module generating programmable 3–30 V outputs for lab-grade instrumentation. IC Role / Device Role / Timing Role: Adjustable main converter core with external DAC-controlled feedback divider for precise voltage setting. Use Value: Achieves ±0.5% output accuracy over temperature using 0.1% resistor network, meeting Class II calibration requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596SX-ADJ | 3 A output, 150 kHz switching, higher RDS(ON) (0.22 Ω), wider VIN (4.5–40 V) | Limited to 3 A loads; lower frequency increases inductor size; less efficient at high current | Choose when cost sensitivity outweighs current demand and board space is not constrained. |
| TPS54560DGQR | 5 A output, 100 kHz–2.5 MHz adjustable frequency, 0.12 Ω RDS(ON), integrated soft-start | Requires external compensation; supports sync clock and power-good signal; smaller 10-pin MSOP package | Prefer when design requires frequency synchronization, tighter transient response, or footprint reduction over thermal robustness. |
Compared with LM2596SX-ADJ and TPS54560DGQR, the LM2678SX-ADJ offers superior thermal performance in TO-263-7, fixed-frequency simplicity for EMI control, and proven reliability in high-temperature industrial environments - making it optimal where ruggedness and ease of qualification matter more than feature density.
Availability
LM2678SX-ADJ is available at Aetrix Electronics and suitable for industrial power supplies, battery management systems, and automotive pre-regulators requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2678SX-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 experience in high-reliability power conversion ICs.
The LM2678 series belongs to TI's SIMPLE SWITCHER® family - designed specifically to simplify high-efficiency DC-DC buck converter implementation using minimal external components and industry-standard magnetics.
FAQ
What is the maximum output current capability of the LM2678SX-ADJ?
The LM2678SX-ADJ delivers up to 5 A of continuous output current under proper thermal conditions - verified across –40°C to 125°C junction temperature with adequate PCB copper area and airflow. Current limit is internally set between 6.1 A (min) and 8.3 A (max) depending on temperature, ensuring safe operation even during short transients.
How do I configure the output voltage for LM2678SX-ADJ?
To configure the output voltage of LM2678SX-ADJ, connect a resistor divider between VOUT and GND, with the midpoint fed to the FB pin. Use R1 (top) and R2 (bottom) such that VOUT = 1.21 V × (1 + R1/R2). For example, 10 kΩ (R2) and 39.2 kΩ (R1) yields 5.0 V. The LM2678SX-ADJ datasheet Table 5.8 specifies VFB = 1.21 V ±1.2% over temperature.
Does LM2678SX-ADJ require an external bootstrap capacitor?
Yes, LM2678SX-ADJ requires a 100 nF ceramic capacitor connected between the CB pin and the SW pin. This bootstrap capacitor enables the internal high-side gate driver to generate sufficient gate-source voltage (>VIN) to fully enhance the DMOS switch, minimizing RDS(ON) and conduction losses. Placement must be low-inductance and adjacent to pins 1 and 3.
What is the recommended minimum input capacitance for LM2678SX-ADJ?
The recommended minimum input capacitance for LM2678SX-ADJ is 100 µF low-ESR electrolytic or polymer capacitor, plus a 0.1 µF ceramic capacitor placed directly at the VIN and GND pins. This combination handles RMS input ripple current (≈2.5 A at 5 A load) and suppresses high-frequency ringing caused by fast switching transitions.
Can LM2678SX-ADJ operate with an input voltage below 8 V?
No, LM2678SX-ADJ has a specified minimum input voltage of 8 V per Recommended Operating Conditions (Section 5.3). Operation below 8 V may result in unstable regulation, dropout, or failure to start - due to insufficient headroom for internal bias generation and gate drive. For sub-8 V inputs, consider alternatives like the LM2671 or TPS54202.
LM2678SX-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)
LM2678SX-ADJ FAQ
1.How can I place an order for LM2678SX-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678SX-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 LM2678SX-ADJ reliable?
The price and inventory of LM2678SX-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2678SX-ADJ is usually 5 days.
3.What payment methods are accepted for LM2678SX-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2678SX-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678SX-ADJ?
LM2678SX-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678SX-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 LM2678SX-ADJ?
For technical support, including LM2678SX-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678SX-ADJ requirements.
6.How does Aetrix verify that LM2678SX-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2678SX-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 LM2678SX-ADJ meets industry standards.
7.What is the process for return or replacement of LM2678SX-ADJ?
All LM2678SX-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2678SX-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 LM2678SX-ADJ part is unused and in its original packaging.
Return procedure for LM2678SX-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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