LM317 PCB Layout: Tips and Best Practices

LM317 is a popular voltage regulator that is widely used in electronic circuits. The LM317 voltage regulator is designed to provide a constant output voltage over a wide range of input voltages. It is a versatile device that can be used in a variety of applications, such as power supplies, battery chargers, and audio amplifiers.

One of the critical aspects of using the LM317 voltage regulator in a circuit is proper PCB layout. The PCB layout plays a vital role in the performance of the LM317 voltage regulator. A well-designed PCB layout can help reduce noise, improve stability, and increase the efficiency of the voltage regulator. Therefore, it is essential to follow some guidelines when designing the PCB layout for LM317 voltage regulators. This article will provide an overview of the LM317 voltage regulator and discuss some best practices for designing a PCB layout for LM317 voltage regulators.

LM317 Voltage Regulator

What is LM317?

LM317 is a three-terminal adjustable voltage regulator that can provide regulated output voltage ranging from 1.2V to 37V. It is a versatile device that can be used in a variety of applications, including power supplies, battery chargers, and audio amplifiers, among others.

How does LM317 work?

LM317 works by adjusting the output voltage based on the input voltage and a reference voltage. The device has an internal reference voltage of 1.25V, and by using an external voltage divider network, the output voltage can be set to the desired value. The device also has built-in protection features, such as thermal shutdown and current limiting, which help to prevent damage to the device and the circuit.

Why use LM317?

LM317 is a popular choice for voltage regulation due to its versatility and ease of use. It can provide a stable output voltage with low ripple and noise, making it suitable for use in sensitive applications. The device is also available in a variety of packages, including TO-220, SOT-223, and SOIC, making it easy to integrate into different circuit designs. Additionally, LM317 is a cost-effective solution for voltage regulation, making it a popular choice for hobbyists and professionals alike.

In summary, LM317 is a reliable and versatile voltage regulator that can be used in a variety of applications. Its ease of use, stability, and cost-effectiveness make it a popular choice for designers and hobbyists alike.

PCB Design for LM317

When designing a printed circuit board (PCB) for the LM317 voltage regulator, there are several factors to consider to ensure optimal performance and reliability. This section will cover the key considerations for designing a PCB for the LM317, including schematic design, layout design, grounding, and decoupling.

Factors to Consider

Before beginning the schematic and layout design for the LM317, it is important to consider the following factors:

  • Input voltage range
  • Output voltage range
  • Load current
  • Thermal requirements
  • Physical size constraints
  • Noise and ripple requirements

By considering these factors, you can ensure that the LM317 circuit is designed to meet the specific requirements of your application.

Schematic Design

The schematic design for the LM317 should follow the manufacturer’s recommended circuit configuration. This typically includes a voltage divider network to set the output voltage, a bypass capacitor at the input, and a load capacitor at the output.

It is also important to ensure that the input and output are properly decoupled to reduce noise and ripple. This can be achieved by adding capacitors in parallel with the input and output pins of the LM317.

Layout Design

When designing the layout for the LM317 circuit, the following guidelines should be followed:

  • Keep the input and output traces as short as possible
  • Place decoupling capacitors as close to the LM317 pins as possible
  • Use a ground plane to reduce noise and improve thermal performance
  • Keep high current traces away from low current traces

By following these guidelines, you can reduce noise and improve the overall performance of the LM317 circuit.


Proper grounding is critical for the performance and reliability of the LM317 circuit. The ground plane should be connected to the LM317 ground pin, and all other ground connections should be made to this ground plane.

It is also important to ensure that there are no ground loops in the circuit, as this can introduce noise and affect the performance of the LM317.


Decoupling capacitors are essential for reducing noise and ripple in the LM317 circuit. Ceramic capacitors are recommended for decoupling, as they have low ESR and ESL.

When selecting decoupling capacitors, it is important to choose capacitors with appropriate capacitance and voltage ratings. The manufacturer’s datasheet should be consulted for recommendations on decoupling capacitor values.

By following these guidelines for schematic and layout design, grounding, and decoupling, you can design a high-performance and reliable PCB for the LM317 voltage regulator.

Tips for LM317 PCB Layout

When designing a PCB layout for an LM317 voltage regulator, there are a few tips that can help ensure optimal performance and reliability. Here are some things to keep in mind:

Keep Components Close Together

To minimize noise and interference, it’s important to keep the LM317 and its associated components as close together as possible. This includes the input and output capacitors, as well as any resistors or diodes used in the circuit. Placing these components in close proximity can help reduce the length of the traces between them, which in turn can minimize the effects of parasitic capacitance and inductance.

Minimize Trace Lengths

In addition to keeping components close together, it’s also important to minimize the length of the traces between them. This can help reduce the resistance and inductance of the circuit, which can improve the regulator’s stability and transient response. When laying out the PCB, try to keep the traces as short and direct as possible, avoiding unnecessary bends or loops.

Use Copper Pour for Heat Dissipation

The LM317 can generate a significant amount of heat, especially when regulating high currents or voltages. To prevent the regulator from overheating, it’s important to provide adequate heat dissipation. One way to do this is to use a copper pour on the PCB, which can help spread the heat away from the regulator and into the surrounding air. When using a copper pour, be sure to connect it to a ground plane or other low-impedance path to ensure good thermal conductivity.

Test and Verify the Design

Finally, it’s important to thoroughly test and verify the LM317 PCB design before putting it into production. This can help identify any potential issues or errors in the layout, such as incorrect component values or inadequate heat dissipation. Use a multimeter or oscilloscope to measure the voltage and current at various points in the circuit, and compare the results to the expected values. If any discrepancies are found, revise the design and test again until the results are satisfactory.

By following these tips, you can design a PCB layout for the LM317 that is optimized for performance, reliability, and ease of use.


In conclusion, designing an LM317 PCB layout is a crucial step in ensuring the proper functioning of voltage regulators. The layout should be designed with careful consideration of the thermal performance of the device, as well as the placement of input and output capacitors.

When designing the layout, it is important to follow the manufacturer’s recommendations and guidelines. This will help to ensure the proper functioning of the device and prevent any potential issues that may arise from poor design choices.

Additionally, it is important to consider the size and shape of the PCB, as well as the location of other components on the board. This will help to minimize noise and interference, which can negatively impact the performance of the voltage regulator.

Overall, designing an LM317 PCB layout requires careful planning and attention to detail. By following the guidelines and recommendations of the manufacturer, designers can ensure the proper functioning of the device and avoid any potential issues that may arise from poor design choices.


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