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Texas Instruments LM2678SX-3.3/NOPB
- Part No.:
- LM2678SX-3.3/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2678SX-3.3/NOPB.pdf
- Description:
- IC REG BUCK 3.3V 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:618
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Product details
Overview
LM2678SX-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 LM2678SX-3.3/NOPB datasheet, LM2678SX-3.3/NOPB pinout, LM2678SX-3.3/NOPB application, or LM2678SX-3.3/NOPB equivalent, key selection criteria include thermal performance in TO-263-7 (KTW), efficiency at 5 A load, feedback configuration for fixed-output use, and compatibility with standard off-the-shelf inductors and Schottky diodes.
Technical Context
The LM2678SX-3.3/NOPB implements a voltage-mode PWM controller with internal 260 kHz oscillator, driving an integrated DMOS high-side switch. Its fixed-output architecture eliminates external feedback resistors - FB pin connects directly to VOUT - simplifying layout and improving regulation stability.
It features built-in thermal shutdown, cycle-by-cycle current limiting (6.1–8.3 A typical limit), and logic-level ON/OFF control with 1.4 V threshold and 50 µA standby current. The switch node (Pin 1) operates between VIN and ~−0.5 V during off-time, requiring careful PCB routing to minimize EMI and ground bounce.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V ±2% over –40°C to 125°C junction temperature, 8–40 V input, 100 mA–5 A load. |
| Max Output Current | 5 A continuous; current limit trips at 6.1–8.3 A depending on temperature - ensures safe overload handling without external sensing. |
| Input Voltage Range | 8 V to 40 V DC - supports wide industrial and automotive battery-derived supplies, including 12 V and 24 V nominal systems. |
| Switching Frequency | 260 kHz ±11% - enables use of compact, standardized off-the-shelf inductors (e.g., 10–22 µH) and reduces EMI compared to lower frequencies. |
| Efficiency | Up to 92% at 12 VIN/5 A (3.3 VOUT); ≥82% typical across full load range - minimizes thermal dissipation in high-current applications. |
| RDS(ON) | 120 mΩ at TJ = 25°C - low conduction loss enables high efficiency without external MOSFETs or heatsinks in moderate-power designs. |
| Standby Current | 50 µA when ON/OFF pin < 0.8 V - enables ultra-low-power system sleep modes without auxiliary LDOs. |
Pinout & Package
LM2678SX-3.3/NOPB is packaged in TO-263-7 (KTW), a surface-mount power package with exposed thermal pad (DAP) soldered to PCB ground plane for optimal thermal performance. Package dimensions: 10.1 mm × 15.24 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SW) | Switch output | Drain of internal DMOS high-side FET; connects to inductor and cathode of external Schottky diode - high dv/dt node requiring short, low-inductance routing. |
| 2 (VIN) | Input supply | Main power input (8–40 V); must be bypassed with low-ESR capacitor placed adjacent to pin - path to GND must be minimal to reduce noise coupling. |
| 3 (CB) | Bootstrap capacitor | Connects to SW via 100 nF ceramic capacitor - provides gate drive voltage > VIN to fully enhance internal FET and minimize RDS(ON). |
| 4 (GND) | Power ground | Primary return path for input/output capacitors and thermal pad - must connect to large copper area for thermal and electrical integrity. |
| 5 (NC) | No connect | Internally unconnected; electrically isolated - no routing or component attachment required. |
| 6 (FB) | Feedback sense | Direct connection to output capacitor (fixed 3.3 V version); internal resistor divider sets regulation point - no external resistors needed. |
| 7 (ON/OFF) | Enable control | Logic-compatible input: >1.4 V = active regulation, <0.8 V = shutdown (50 µA IQ); internal 20 µA pull-up allows floating for always-on operation. |
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 while maintaining >90% efficiency at 5 A. |
| Fixed 3.3 V output with ±2% tolerance | Guaranteed accuracy across –40°C to 125°C and full load range - removes calibration overhead and supports tight-tolerance digital rail requirements. |
| 260 kHz fixed-frequency PWM | Enables predictable EMI filtering and consistent inductor sizing; avoids frequency jitter issues seen in variable-frequency controllers. |
| Thermal shutdown + current limiting | Protects against sustained overload or poor heatsinking - automatically recovers after fault removal without latch-up or external circuitry. |
| ON/OFF pin with 50 µA standby | Supports system-level power sequencing and low-power sleep states - compatible with microcontroller GPIO without level-shifting. |
Applications
| Industrial PLC Power Supply | Automotive Body Control Module |
|---|---|
Use Scenario: Providing stable 3.3 V rail for microcontrollers, CAN transceivers, and sensor interfaces in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Primary buck regulator converting 24 V DC bus to regulated 3.3 V - handles transient loads up to 5 A during I/O activation bursts. Use Value: High efficiency (>85% at 24 VIN/3 A) reduces heat buildup in enclosed enclosures; ±2% output tolerance ensures reliable MCU operation across ambient temperature swings. | Use Scenario: Generating 3.3 V for infotainment SoCs and ADAS sensors in 12 V vehicle electrical systems with cold-crank (6.5 V) and load-dump (40 V) transients. IC Role / Device Role / Timing Role: Pre-regulator stepping down raw battery voltage before LDOs - withstands 40 V input surges and maintains regulation down to 8 V during cranking. Use Value: 8–40 V input range covers full automotive operating envelope; 50 µA shutdown current extends battery life during vehicle sleep mode. |
| Medical Point-of-Care Device | Networking Equipment Midplane |
Use Scenario: Powering FPGA configuration logic and low-noise ADCs in portable ultrasound or patient monitors where thermal management is constrained. IC Role / Device Role / Timing Role: High-current 3.3 V source with minimal external components - used alongside low-ESR ceramic output capacitors to meet ripple <20 mVpp spec. Use Value: TO-263 thermal pad enables direct PCB copper heatsinking - achieves <35°C/W θJA with 1.0 in² copper, avoiding discrete heatsinks in space-limited enclosures. | Use Scenario: Distributed 3.3 V generation across backplane-fed telecom or enterprise switch midplanes with multiple hot-swap domains. IC Role / Device Role / Timing Role: Local point-of-load regulator per board slot - controlled via ON/OFF pin for independent power cycling and fault isolation. Use Value: Logic-level enable allows direct interface with system management controllers; 260 kHz frequency avoids interference with Ethernet PHY clock harmonics. |
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-3.3/NOPB | 3 A max output, 150 kHz switching frequency, higher RDS(ON) (160 mΩ), wider VIN (4.5–40 V). | Lower current capability and slower response - suitable only for ≤3 A loads; less efficient at high current due to higher conduction loss. | Select when cost sensitivity outweighs current/efficiency needs and 3 A suffices. |
| TPS54560BDDAR | 5 A, 60 V max input, adjustable output, 100–2500 kHz programmable frequency, integrated soft-start. | Requires external feedback resistors and compensation - more flexible but increases design time and BOM count. | Select when input exceeds 40 V or adjustable output is required; not drop-in for fixed 3.3 V use. |
Compared with LM2596SX-3.3/NOPB, LM2678SX-3.3/NOPB delivers 67% higher current and 12% higher peak efficiency; versus TPS54560BDDAR, it offers simpler fixed-output implementation but lacks input voltage headroom and frequency flexibility.
Availability
LM2678SX-3.3/NOPB is available at Aetrix Electronics and suitable for industrial PLC power supplies, automotive body control modules, and medical point-of-care devices requiring stable component supply and long-term manufacturability.
Supply support for LM2678SX-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-reliability power conversion solutions.
The LM2678 series belongs to TI's SIMPLE SWITCHER® family - designed specifically for engineers needing fast, robust, low-component-count DC/DC buck regulators for industrial, automotive, and medical applications.
FAQ
What is the maximum input voltage rating for LM2678SX-3.3/NOPB?
The absolute maximum input voltage for LM2678SX-3.3/NOPB is 45 V, but the recommended operating range is 8 V to 40 V DC. Operation above 40 V risks exceeding internal device stress limits and may trigger overvoltage protection or cause permanent damage. For automotive applications with load-dump transients, external clamping (e.g., TVS diode) is advised to keep VIN within 40 V.
Does LM2678SX-3.3/NOPB require external feedback resistors?
No, LM2678SX-3.3/NOPB does not require external feedback resistors. As a fixed-output variant, it contains an internal resistor divider that sets the regulated output to 3.3 V. The FB pin must be connected directly to the output capacitor's positive terminal - no external components are needed for voltage setting, simplifying layout and improving accuracy.
How is thermal performance managed in the TO-263-7 (KTW) package of LM2678SX-3.3/NOPB?
LM2678SX-3.3/NOPB in KTW package uses an exposed thermal pad (DAP) that must be soldered to a large PCB copper area tied to GND. With 1.0064 in² (7.4× package area) of 1 oz. copper and 12 thermal vias, θJA drops to 26°C/W - enabling 5 A operation at ≤60°C ambient without a heatsink. Poor thermal pad connection degrades performance significantly.
Can LM2678SX-3.3/NOPB be synchronized to an external clock?
No, LM2678SX-3.3/NOPB cannot be synchronized to an external clock. It uses an internal fixed-frequency 260 kHz oscillator with ±11% tolerance. There is no SYNC pin or frequency adjustment capability. For applications requiring synchronization (e.g., multi-rail systems), consider alternatives like TPS54560BDDAR or LM5115.
What is the minimum load requirement for stable regulation with LM2678SX-3.3/NOPB?
LM2678SX-3.3/NOPB has no minimum load requirement for stable regulation. It maintains ±2% output accuracy from 0 A to 5 A under all specified conditions. The device operates in discontinuous conduction mode (DCM) at light loads, with automatic pulse-skipping to maintain efficiency - verified in datasheet Figure 5-4 and Section 6.4.2.
LM2678SX-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:
- Tape & Reel (TR)
- 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)
LM2678SX-3.3/NOPB FAQ
1.How can I place an order for LM2678SX-3.3/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678SX-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 LM2678SX-3.3/NOPB reliable?
The price and inventory of LM2678SX-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 LM2678SX-3.3/NOPB is usually 5 days.
3.What payment methods are accepted for LM2678SX-3.3/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2678SX-3.3/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678SX-3.3/NOPB?
LM2678SX-3.3/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678SX-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 LM2678SX-3.3/NOPB?
For technical support, including LM2678SX-3.3/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678SX-3.3/NOPB requirements.
6.How does Aetrix verify that LM2678SX-3.3/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2678SX-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 LM2678SX-3.3/NOPB meets industry standards.
7.What is the process for return or replacement of LM2678SX-3.3/NOPB?
All LM2678SX-3.3/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2678SX-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 LM2678SX-3.3/NOPB part is unused and in its original packaging.
Return procedure for LM2678SX-3.3/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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