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Texas Instruments LM2678S-3.3/NOPB
- Part No.:
- LM2678S-3.3/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2678S-3.3/NOPB.pdf
- Description:
- IC REG BUCK 3.3V 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:145
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Product details
Overview
LM2678S-3.3/NOPB from Texas Instruments is a monolithic step-down (buck) DC-DC switching regulator delivering up to 5 A output current with fixed 3.3 V output, 8–40 V input range, 260 kHz fixed-frequency operation, and ±2% output voltage tolerance over full line/load/temperature. It integrates a 120 mΩ DMOS high-side switch and supports ON/OFF control for low-power standby.
For engineers reviewing the LM2678S-3.3/NOPB datasheet, LM2678S-3.3/NOPB pinout, LM2678S-3.3/NOPB application, or LM2678S-3.3/NOPB equivalent, key selection criteria include thermal performance in TO-263-7 (KTW), efficiency at 5 A load (≥82%), feedback configuration for fixed-output use, and compatibility with standard off-the-shelf inductors and Schottky diodes.
Technical Context
The LM2678S-3.3/NOPB implements a fixed-frequency PWM buck controller with internal 260 kHz oscillator and integrated 120 mΩ DMOS high-side switch. Its feedback loop uses an internal resistor divider for 3.3 V regulation, eliminating external resistors-pin 6 (FB) connects directly to output.
It features active current limiting (6.1–8.3 A), thermal shutdown, and ON/OFF control with 1.4 V threshold and 50 µA standby current. The device operates across –40°C to +125°C junction temperature and requires bootstrapping via pin 3 (CB) to drive the high-side FET gate above VIN.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V ±2% (3.234–3.366 V at 25°C; 3.201–3.399 V over –40°C to 125°C) |
| Input Voltage Range | 8 V to 40 V - supports wide industrial and battery-derived supplies without pre-regulation |
| Max Output Current | 5 A continuous - enables single-chip conversion for mid-power systems (e.g., FPGA core rails, DSP supplies) |
| Switching Frequency | 260 kHz ±11% - enables use of compact, low-cost off-the-shelf inductors (e.g., 10 µH) and reduces EMI vs higher frequencies |
| RDS(ON) | 0.12 Ω typical at 25°C - minimizes conduction loss and supports >82% efficiency at 12 VIN/5 A |
| Standby Current | 50 µA max at 25°C - enables low-power system sleep modes without external disconnect circuitry |
| Thermal Resistance (RθJA) | 56 °C/W (KTW package, 0.136 in² copper) - defines heatsink-free power capability (~3.5 W dissipation at ΔT = 200°C) |
Pinout & Package
LM2678S-3.3/NOPB is packaged in KTW (TO-263-7), a surface-mount thermally enhanced variant of TO-220 with exposed DAP connected to GND. The 7-pin layout supports high-current routing and PCB heat spreading.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch output | Drain node of internal DMOS FET - connects 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 |
| 3 (CB) | Bootstrap capacitor | Connects to SW via 100 nF ceramic capacitor - generates gate drive voltage > VIN for high-side FET turn-on |
| 4 (GND) | Power ground | Primary return path for input/output capacitors and internal circuitry; DAP must be soldered to large copper area |
| 5 (NC) | No connect | Internally unconnected - must remain floating; no routing or copper fill required |
| 6 (FB) | Feedback input | Direct connection to output for fixed 3.3 V version - internal resistor divider sets regulation point; no external resistors needed |
| 7 (ON/OFF) | Enable control | Logic-level input: ≥1.4 V = active, ≤0.8 V = shutdown; 20 µA internal pull-up; clamped to 7 V max |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120 mΩ DMOS switch | Eliminates need for external high-side MOSFET and driver, reducing BOM count and layout complexity |
| Fixed 3.3 V output with internal feedback divider | Removes external resistor network - improves accuracy, reduces drift, and simplifies layout near sensitive FB node |
| 260 kHz fixed-frequency PWM | Enables predictable EMI filtering and consistent inductor sizing across designs using TI-recommended parts |
| ON/OFF control with 50 µA standby | Allows system-level power sequencing and deep-sleep states without auxiliary LDO or discrete MOSFET switches |
| Thermal shutdown + current limit | Provides autonomous fault protection during overload, short-circuit, or inadequate heatsinking - no external sensing required |
Applications
| Industrial PLC I/O Power | Embedded Computing Core Rail |
|---|---|
Use Scenario: Powering isolated digital I/O modules in programmable logic controllers requiring clean, regulated 3.3 V from 24 V DC field bus. IC Role / Device Role / Timing Role: Primary step-down regulator converting 24 V bus to 3.3 V for microcontroller, level shifters, and optocoupler drivers. Use Value: Delivers 5 A peak current for burst-mode I/O activation while maintaining ±2% regulation under 10–90% load transients. | Use Scenario: Supplying core voltage to ARM Cortex-A/M series processors in edge gateway devices operating from 12 V or 24 V DC inputs. IC Role / Device Role / Timing Role: High-current buck converter providing stable 3.3 V rail with fast transient response for CPU DVFS transitions. Use Value: Achieves ≥82% efficiency at full 5 A load, minimizing thermal load on compact fanless enclosures. |
| Battery-Powered Test Equipment | Automotive Body Control Module |
Use Scenario: Portable handheld test instruments powered by 12 V sealed lead-acid or LiFePO₄ batteries with wide discharge range (10–14.4 V). IC Role / Device Role / Timing Role: Input-flexible buck regulator maintaining 3.3 V for MCU, ADC, and display interface despite battery sag. Use Value: Operates down to 8 V input, enabling full functionality until battery reaches end-of-discharge; 50 µA shutdown extends shelf life. | Use Scenario: Powering microcontrollers and CAN transceivers in non-safety-critical automotive body electronics (e.g., door modules, seat controls). IC Role / Device Role / Timing Role: Primary 3.3 V supply derived from 12 V vehicle battery with load dump immunity support via input capacitor design. Use Value: Qualified for –40°C to +125°C operation and withstands 40 V transients when paired with appropriate input TVS. |
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-3.3/NOPB | Lower 3 A output current; 150 kHz switching frequency; higher RDS(ON) (0.16 Ω) | Suitable for <3 A loads only; requires larger inductor; lower efficiency at 5 A | Select when cost sensitivity outweighs current/efficiency requirements and board space allows larger magnetics. |
| TPS54560BQPWPRQ1 | Automotive-grade (AEC-Q100); 60 V max input; adjustable output; 500 kHz switching; integrated compensation | Supports wider input (6–60 V), higher reliability, but requires external feedback resistors and more complex layout | Select for automotive applications requiring qualification, extended input range, or programmable output voltage. |
Compared with LM2596S-3.3/NOPB, LM2678S-3.3/NOPB delivers 67% higher current and better efficiency at full load; compared with TPS54560BQPWPRQ1, it offers simpler fixed-output implementation and lower component count but lacks automotive qualification and input voltage headroom.
Availability
LM2678S-3.3/NOPB is available at Aetrix Electronics and suitable for industrial PLC power supplies, embedded computing core rails, and battery-powered test equipment requiring stable component supply and long-term production continuity.
Supply support for LM2678S-3.3/NOPB 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-efficiency DC-DC conversion.
The LM2678 series belongs to TI's SIMPLE SWITCHER® power converter family, designed to simplify robust, high-current buck regulator implementation using minimal external components and industry-standard passives.
FAQ
What is the maximum input voltage rating for LM2678S-3.3/NOPB?
The absolute maximum input voltage for LM2678S-3.3/NOPB is 45 V, but the recommended operating range is 8 V to 40 V. Operation above 40 V risks exceeding safe operating area limits and may trigger internal protection circuits. For sustained reliability, designs should maintain VIN ≤ 40 V with margin for transients.
Does LM2678S-3.3/NOPB require external feedback resistors?
No. LM2678S-3.3/NOPB is a fixed-output variant with internal resistor divider connected to pin 6 (FB). For proper regulation, FB must be connected directly to the output capacitor - no external resistors are needed or permitted. Adding external resistors will disrupt the 3.3 V setpoint.
What thermal performance can be expected from LM2678S-3.3/NOPB in KTW package?
In the KTW (TO-263-7) package with 0.136 in² copper pad, LM2678S-3.3/NOPB has RθJA = 56 °C/W. At 5 A output and 12 V input (≈3.5 W dissipation), junction-to-ambient rise is ~196°C - requiring either heatsinking or derating. With 0.4896 in² copper, RθJA drops to 35 °C/W, enabling full 5 A operation at ambient ≤ 50°C.
Can LM2678S-3.3/NOPB be synchronized to an external clock?
No. LM2678S-3.3/NOPB uses an internal fixed-frequency 260 kHz oscillator with no synchronization input. Frequency variation is ±11% over temperature and supply. For synchronized operation, consider alternatives like TPS54560BQPWPRQ1 or LM5116-based designs.
What is the purpose of the CB pin on LM2678S-3.3/NOPB?
The CB (bootstrap capacitor) pin on LM2678S-3.3/NOPB connects to the switch node (SW) via a 100 nF ceramic capacitor. It provides the gate drive voltage boost needed to fully enhance the internal high-side DMOS FET - ensuring low RDS(ON) and high efficiency. Omitting or undersizing this capacitor causes erratic switching and thermal failure.
LM2678S-3.3/NOPB 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:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- 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-3.3/NOPB FAQ
1.How can I place an order for LM2678S-3.3/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678S-3.3/NOPB 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-3.3/NOPB reliable?
The price and inventory of LM2678S-3.3/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2678S-3.3/NOPB is usually 5 days.
3.What payment methods are accepted for LM2678S-3.3/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2678S-3.3/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678S-3.3/NOPB?
LM2678S-3.3/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678S-3.3/NOPB 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-3.3/NOPB?
For technical support, including LM2678S-3.3/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678S-3.3/NOPB requirements.
6.How does Aetrix verify that LM2678S-3.3/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2678S-3.3/NOPB 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-3.3/NOPB meets industry standards.
7.What is the process for return or replacement of LM2678S-3.3/NOPB?
All LM2678S-3.3/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2678S-3.3/NOPB, 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-3.3/NOPB part is unused and in its original packaging.
Return procedure for LM2678S-3.3/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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