Step-Down Adjustable Regulator Texas Instruments LM2678S-ADJ, Input 8–40 V, Output 1.2–37 V, Package TO-263-7

The Texas Instruments LM2678S-ADJ is an adjustable step-down (buck) switching regulator in a TO-263-7 package designed for DC-DC conversion in power-supply designs. It accepts input voltages from 8 to 40 V and provides an adjustable output range from 1.2 to 37 V, enabling flexible voltage regulation for a variety of electronic systems. The component is intended for use where a wide input range and a configurable regulated output are required, and its TO-263-7 package supports thermal performance appropriate for board-mounted power modules.

Advantages

The LM2678S-ADJ offers a wide input voltage range and a broad adjustable output span, reducing the need for multiple regulator variants in designs. Its switching regulator topology improves efficiency compared with linear regulators when stepping down higher input voltages. The TO-263-7 package provides a compact footprint with thermal conduction suitable for moderate power dissipation on standard PCBs. The device is compatible with common external components used in buck converter topologies, making it straightforward to integrate into existing power-supply layouts.

Suitable for

• Embedded systems requiring adjustable regulated DC supply
• Industrial electronics with wide input voltage sources
• Prototyping and development of power-supply modules
• Battery-powered or vehicle electrical systems with higher input voltages
• Custom electronics where a single regulator must cover multiple output rails

Key specifications

• Topology: Step-down (buck) switching regulator
• Input voltage range: 8–40 V
• Adjustable output voltage range: 1.2–37 V
• Package type: TO-263-7 (surface-mount power package)
• Adjustable output via external feedback network
• Intended for board-mounted applications with external inductor and capacitors

How to use

Integrate the LM2678S-ADJ into a buck converter circuit following the manufacturer’s recommended application schematic: connect the input supply to the input pin with suitable input decoupling, place the switching inductor, diode (or synchronous arrangement if applicable), and output capacitors according to layout guidance to minimize EMI and voltage ripple. Set the desired output voltage using an external resistor divider between the output and feedback pin, referencing the device’s feedback voltage specification to calculate resistor values. Ensure adequate copper area or a thermal pad under the package to aid heat dissipation for higher load currents.

Recommendations

For reliable operation, use low-ESR output capacitors, a properly rated inductor for the expected current, and follow layout recommendations to keep the switching loop area small. Verify thermal performance under worst-case input voltage and load conditions and add heat sinking or improved PCB thermal vias if required.