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Texas Instruments LM2678T-ADJ/NOPB
- Part No.:
- LM2678T-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-220-7 Formed Leads
- Datasheet:
-
LM2678T-ADJ/NOPB.pdf
- Description:
- IC REG BUCK ADJ 5A TO220-7
- Quantity:
- Payment:
- Shipping:
Inventory:556
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Product details
Overview
LM2678T-ADJ/NOPB from Texas Instruments is a monolithic step-down (buck) DC-DC switching regulator IC delivering up to 5A output current with adjustable output voltage (1.2V to 37V), 260kHz fixed-frequency operation, 120mΩ internal DMOS switch, and ±2% output voltage tolerance over full line/load/temperature range. It serves as a high-efficiency (>90%) primary power conversion stage in industrial power supplies and battery-based systems.
For engineers reviewing the LM2678T-ADJ/NOPB datasheet, LM2678T-ADJ/NOPB pinout, LM2678T-ADJ/NOPB application, or LM2678T-ADJ/NOPB equivalent, key selection criteria include input voltage range (8–40V), thermal performance in TO-263 package, feedback accuracy (1.21V typical VFB), ON/OFF control interface, and compatibility with standard off-the-shelf inductors and Schottky diodes.
Technical Context
The LM2678T-ADJ/NOPB integrates a high-side DMOS power switch, fixed 260kHz PWM oscillator, current-mode control loop, thermal shutdown, and cycle-by-cycle current limiting. Its feedback architecture uses an internal 1.21V reference with external resistor divider for precise output regulation across 1.2V–37V.
It operates in continuous conduction mode (CCM) at full load and transitions to discontinuous conduction mode (DCM) under light loads. The ON/OFF pin enables direct logic-level enable/disable with 50μA standby current, while the CB pin supports bootstrap gate drive for efficient high-side FET operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output current | 5A maximum continuous load capability without external heatsink under optimized PCB layout. |
| Input voltage range | 8V to 40V - supports wide-range industrial and battery-derived inputs (e.g., 12V/24V/36V nominal systems). |
| Output voltage range | 1.2V to 37V - set via external resistor divider on FB pin; enables single BOM for multiple output rails. |
| Switch RDS(on) | 0.12Ω typical at 25°C - minimizes conduction loss and enables >90% efficiency at 5A with proper layout. |
| Oscillator frequency | 260kHz fixed - allows use of compact, low-cost off-the-shelf inductors (e.g., 10–47μH) and reduces EMI compared to MHz-range converters. |
| Feedback voltage | 1.21V ±1.2% - defines output accuracy; sets VOUT = 1.21V × (1 + R1/R2) with minimal temperature drift. |
| Standby current | 50μA max at TJ = 25°C - enables ultra-low-power shutdown in battery-backed or energy-sensitive applications. |
| Thermal shutdown | Activated at TJ ≥ 165°C - protects device during overload or poor heatsinking; auto-recovery on cooldown. |
Pinout & Package
LM2678T-ADJ/NOPB is supplied in the KTW (TO-263-7) thermally enhanced surface-mount package, featuring a 10.1mm × 15.24mm outline and exposed DAP (die attach pad) electrically connected to GND for optimal thermal dissipation and EMI control.
| 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 - requires low-inductance routing. |
| 2 (IN) | Input supply | Main power input (8–40V); must be bypassed with low-ESR capacitor placed adjacent to pin to suppress high-frequency ripple. |
| 3 (CB) | Bootstrap capacitor | Connects to SW via 100nF ceramic capacitor to generate gate drive voltage > VIN for full FET enhancement. |
| 4 (GND) | Power ground | Primary return path for IN, SW, and FB; must be tied to large copper plane and connected to DAP for thermal and noise integrity. |
| 5 (NC) | No connect | Internally unconnected; leave floating - no routing or soldering required. |
| 6 (FB) | Feedback sense | High-impedance input (85nA bias) monitoring output voltage divider; sensitive to noise - route away from SW and inductor. |
| 7 (ON/OFF) | Enable control | Logic-compatible input: ≥1.4V = active regulation; ≤0.8V = shutdown (50μA IQ); internal 20μA pull-up simplifies interface. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 120mΩ DMOS switch | Eliminates need for external high-current MOSFET and driver, reducing BOM count and layout complexity for 5A buck designs. |
| Fixed 260kHz oscillator | Enables predictable EMI profile and consistent inductor sizing - avoids variable-frequency jitter and simplifies filter design. |
| ±2% output tolerance | Guaranteed over –40°C to +125°C junction temperature, full line/load - meets tight regulation requirements without post-production trimming. |
| ON/OFF pin with 50μA standby | Supports system-level power sequencing and battery conservation; compatible with microcontroller GPIO without level-shifting. |
| Thermal shutdown + current limit | Provides autonomous fault protection: cycle-by-cycle current limit (6.1–8.3A) and thermal cutoff prevent damage during short-circuit or overheating. |
| SIMPLE SWITCHER® design support | WEBENCH® Power Designer integration delivers validated schematics, BOMs, and efficiency simulations - accelerates time-to-first-power by >50%. |
Applications
| Industrial Power Supply | Battery Charger Pre-regulator |
|---|---|
Use Scenario: 24V input converted to 5V/3.3V for PLC I/O modules and sensor interfaces in factory automation cabinets. IC Role / Device Role / Timing Role: Primary non-isolated buck converter providing stable, high-current intermediate rail with fast transient response to motor start-up surges. Use Value: Delivers 5A at >90% efficiency with minimal thermal rise on standard 2oz copper, eliminating need for forced air cooling in sealed enclosures. | Use Scenario: 36V Li-ion battery pack stepped down to 12.6V constant-voltage charge stage before linear charging IC. IC Role / Device Role / Timing Role: High-efficiency preregulator reducing heat dissipation in downstream linear charger; ON/OFF pin synchronized to battery management system. Use Value: Reduces power loss by >70% versus linear preregulation, extending usable battery capacity and enabling compact thermal design. |
| Test Equipment Power Rail | Telecom Remote Power Unit |
Use Scenario: Benchtop multimeter or oscilloscope requiring clean, low-noise ±15V and +5V rails from universal AC adapter (12–40V DC bus). IC Role / Device Role / Timing Role: Adjustable-output buck regulator generating precision analog rails; FB pin filtered to minimize switching noise coupling into sensitive analog circuitry. Use Value: Achieves <10mVpp output ripple with standard 47μH inductor and 470μF low-ESR capacitor - meets metrology-grade stability requirements. | Use Scenario: Outdoor telecom node powered from 48V PoE++ or solar array, requiring robust 3.3V/5V rails for RF transceivers and baseband processors. IC Role / Device Role / Timing Role: Primary DC-DC converter operating across –40°C to +85°C ambient; thermal shutdown prevents latch-up during solar thermal cycling. Use Value: Maintains regulation and 5A output capability even at 125°C junction temperature - qualified for extended outdoor deployment without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596T-ADJ/NOPB | 3A output rating, 150kHz switching frequency, higher RDS(on) (0.22Ω), wider VIN (4–40V). | Lower current and efficiency; suitable only for ≤3A loads where cost sensitivity outweighs thermal or size constraints. | Select when budget limits dominate and full 5A capability is unnecessary. |
| TPS54560DGQR | 5A output, 100V input rating, adjustable frequency (100–2500kHz), integrated soft-start, smaller MSOP-10 package. | Higher input voltage range and programmable frequency enable compact designs in automotive or HV industrial systems. | Select when input exceeds 40V or board space is constrained and higher-frequency magnetics are preferred. |
Compared with LM2596T-ADJ/NOPB, LM2678T-ADJ/NOPB delivers 67% higher output current and 14% higher peak efficiency; compared with TPS54560DGQR, it offers lower system cost and simpler layout due to fixed frequency and fewer external components, though with less input voltage headroom and no soft-start control.
Availability
LM2678T-ADJ/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, battery charger pre-regulators, test equipment power rails, and telecom remote power units requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2678T-ADJ/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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management technologies with over 90 years of innovation history.
The LM2678 series belongs to TI's SIMPLE SWITCHER® power converter family, designed specifically to simplify high-current DC-DC buck regulator implementation using minimal external components and industry-standard passives.
FAQ
What is the minimum input voltage required for stable operation of the LM2678T-ADJ/NOPB?
The LM2678T-ADJ/NOPB requires a minimum input voltage of 8V to maintain regulation across its full output range. Below this threshold, the internal control loop cannot sustain duty cycle or gate drive integrity, resulting in dropout or shutdown. This specification is verified across –40°C to +125°C junction temperature and applies regardless of output voltage setting.
Can the LM2678T-ADJ/NOPB be used with an output voltage below 1.2V?
No - the LM2678T-ADJ/NOPB has a fixed internal feedback reference voltage of 1.21V ±1.2%, and its datasheet-specified output range is 1.2V to 37V. Attempting to configure for sub-1.2V outputs violates the guaranteed electrical characteristics and results in inaccurate regulation, as the error amplifier cannot properly close the loop below the reference threshold.
How does the ON/OFF pin behave when left unconnected on the LM2678T-ADJ/NOPB?
When the ON/OFF pin is left floating, the internal 20μA pull-up current source drives it to a logic-high state, enabling normal regulator operation. This default-active behavior eliminates the need for external pull-up resistors in most applications, though designers should verify that PCB leakage paths do not inadvertently pull the pin low in high-impedance environments.
What thermal performance can be expected from the LM2678T-ADJ/NOPB in the KTW package without a heatsink?
In the KTW (TO-263-7) package mounted on a 1.0064 in² copper area with 12 vias to inner layers, the LM2678T-ADJ/NOPB achieves a junction-to-ambient thermal resistance (RθJA) of 26°C/W. At 5A output and 12V input, typical power dissipation is ~1.5W, resulting in ~39°C junction-to-ambient rise - well within the –40°C to +125°C operating range without additional heatsinking.
Is the LM2678T-ADJ/NOPB RoHS-compliant and lead-free?
Yes - the LM2678T-ADJ/NOPB carries the /NOPB suffix, indicating "No Lead (Pb)-Free" per TI's packaging nomenclature, and fully complies with RoHS Directive 2011/65/EU. It uses matte-tin lead finish on all terminals and contains no intentionally added lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE).
LM2678T-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-220-7 Formed Leads
- Packaging:
- Tube
- Product Status:
- Active
- 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
LM2678T-ADJ/NOPB FAQ
1.How can I place an order for LM2678T-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2678T-ADJ/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 LM2678T-ADJ/NOPB reliable?
The price and inventory of LM2678T-ADJ/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2678T-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LM2678T-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2678T-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2678T-ADJ/NOPB?
LM2678T-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2678T-ADJ/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 LM2678T-ADJ/NOPB?
For technical support, including LM2678T-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2678T-ADJ/NOPB requirements.
6.How does Aetrix verify that LM2678T-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2678T-ADJ/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 LM2678T-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LM2678T-ADJ/NOPB?
All LM2678T-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2678T-ADJ/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 LM2678T-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LM2678T-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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