Introduction

When it comes to voltage regulation in electronic circuits, two popular components stand out: the LM317 and its variant, the LM317T. In today’s post, we will explore the differences and similarities between LM317 and LM317T.

LM317 vs LM317T: similarity

The LM317 and LM317T are adjustable positive voltage regulators manufactured by Texas Instruments. They belong to the same LM317 series and share similar characteristics and functionalities.

Figure1-LM317 vs LM317T

LM317 vs LM317T: Overview

LM317: The Versatile Regulator

The LM317 is a workhorse in the realm of voltage regulation. It's known for its versatility, making it a go-to choice for many applications. One of its standout features is its adjustable output voltage. By using external resistors, you can set the output voltage to your desired level, making it suitable for various projects where precise voltage control is necessary.

LM317T: The TO-220 Package Variant

The LM317T is essentially a variant of the LM317, differing primarily in its physical packaging. The "T" in LM317T indicates the TO-220 package, a widely used form factor in electronics. This package offers better thermal dissipation characteristics, making it suitable for applications where heat dissipation is a concern. It can handle higher power dissipation compared to the standard LM317, which is crucial in high-current applications.

The LM317T has a higher maximum current output capability (typically 1.5A), operates in a higher input voltage range (typically 40V), and has better linearity and temperature stability.

In contrast, LM317 has a lower input operating voltage range, usually below 35V, and the maximum output current is also smaller, only about 1A.

LM317 vs LM317T: Pinout

Adjust: Thid pins adjust the output voltage

Output Voltage (Vout): The regulated output voltage set by the adjust pin can be obtained from this pin.

Input Voltage (Vin): The input voltage that has to be regulated is given to this pin.

The LM317T has the same pinout as the LM317 since it is essentially the same regulator but in the TO-220 package.

Figure2-LM317 pinout

How to Choose Between LM317 and LM317T?

When deciding between the LM317 and LM317T, consider the following factors:

1. Heat Dissipation Requirements:

If your application involves higher current levels that could lead to significant heat dissipation, the LM317T's TO-220 package is the preferred choice.

2. Board Space and Mounting Considerations:

The TO-220 package of the LM317T might take up more board space compared to the standard LM317. Consider your available board real estate when making a decision.

3. Cost and Availability:

The LM317T, being a widely used package, might be more readily available and cost-effective due to its popularity.

4. Voltage Regulation Precision:

Both the LM317 and LM317T provide similar voltage regulation performance. The choice between them is more about packaging and thermal considerations.

Conclusion: The Right Regulator for the Right Job

In summary, the LM317 and LM317T are both exceptional voltage regulators, each with its own strengths. If your application demands higher power dissipation and thermal considerations, the LM317T in its TO-220 package is the way to go. However, for general-purpose applications where space constraints and cost are crucial, the standard LM317 might be the more fitting choice.

Ultimately, the decision boils down to your specific project requirements. Carefully evaluate your needs; you'll find the perfect voltage regulator to power your electronics.

Notes:  the choice between the LM317 and LM317T depends on the specific needs of your project. Always refer to the datasheets and consider factors like power dissipation, board space, and cost before making a final decision.