LM317T Voltage Regulator: Pinout, Datasheet and Equivalent

The LM317T is a versatile and widely-used adjustable voltage regulator. As a monolithic integrated circuit (IC), it allows for output voltage regulation across a wide range, providing flexibility in various applications. This IC is capable of delivering more than 1.5A of load current with an adjustable output voltage ranging from 1.2V to 37V. The circuit is especially popular in DIY electronics projects, power supplies, and battery chargers as its ease of use, reliability, and range of features.

1. What is the LM317T Voltage Regulator?

2. LM317T Pinout, CAD Model, Symbol and Footprint

3. Features of the IC LM317T

4. LM317T Circuit Technical Specifications

5. Where and How to Use the LM317?

6. LM317T Applications

7. Frequently Asked Questions [FAQ]

What is the LM317T Voltage Regulator?

The LM317 T is a versatile monolithic integrated circuit (IC) designed as an adjustable 3-terminal positive-voltage regulator. Capable of supplying over 1.5A of load current, with an output voltage that can adjust from 1.2V to 37V, making it suitable for a wide range of applications.

One of the key features of the circuit is its simplicity: the output voltage determine using just a resistive voltage divider, eliminating the need for multiple fixed regulators in inventory. This makes it easy to integrate into various projects without requiring complex configurations.

The LM317 T incorporates several built-in protections, including current limiting, thermal shutdown, and safe operating area (SOA) control. These safety features help prevent overheating and component damage under heavy loads or faulty conditions.

LM317T Adjustable Voltage Regulator Popular Applications:

LM317T 12V to 5V: Use in step-down converters.

LM317T 3.3V: For low-voltage applications, such as powering sensors and microcontrollers.

LM317T 5V Circuit: Commonly use for powering USB devices or small projects requiring 5V regulation.

LM317T Pinout, CAD Model, Symbol and Footprint

The LM317 T comes in a standard TO-220 package, a popular form factor for voltage regulators. Below is the pin configuration:

LM317T Circuit Diagram

LM317T Schematic Diagram:

The basic schematic for the LM317 T voltage regulator is straightforward. Apply the input voltage to Pin 3 (Vin), while take the output voltage from Pin-2 (Vout). Connect Pin-1 (Adjust) to a resistive voltage divider network that sets the output voltage.

Features of the IC LM317T

The circuit offers several significant features that make it suitable for a broad range of applications:

Output Voltage Range (1.2V to 37V) 

The IC offers a broad adjustable voltage range from 1.2V to 37V, which makes it highly versatile. By adjusting external resistors, users can set the output voltage to meet the requirements of various devices and circuits, providing flexibility in design.

Output Current in Excess of 1.5A 

The regulator is capable of delivering more than 1.5A of output current, which is sufficient for powering many electronic devices and circuits, from simple projects to more complex systems that require moderate to high current loads.

0.1% Line and Load Regulation 

The component maintains excellent voltage stability with 0.1% line and load regulation. This means that the output voltage remains consistent even with fluctuations in the input voltage or variations in the load, making it highly reliable in voltage-sensitive applications.

Floating Operation for High Voltages 

The chip can operate in a floating configuration, which means it can regulate voltages from high-input sources relative to ground. As long as the input-to-output differential does not exceed the maximum limit, it can use for high-voltage applications, offering more versatility in power management.

Complete Series of Protections 

The LM317 T incorporates built-in current limiting, thermal shutdown, and Safe Operating Area (SOA) control. These protective features prevent damage under faulty conditions, such as overheating or excessive current, ensuring the regulator works safely and efficiently under a wide range of operating conditions.

Output-Transistor Safe Operating Area (SOA) Compensation 

The IC has a compensated safe operating area for its output transistor. This means the regulator adjusts its performance to keep the output transistor within safe limits, reducing the risk of failure as thermal or current overload, which extends the lifespan and reliability of the regulator in various applications.

These features make the circuit not only a flexible and reliable voltage regulator but also a safe, durable choice for a wide range of power management tasks in electronics.

LM317T Circuit Technical Specifications

LM317T Equivalent and Alternative

LM317T TO220 Package

This is the standard through-hole package with 3 pins. Commonly use in high-power applications and offers good heat dissipation, making it ideal for circuits where the regulator will handle higher current and require efficient cooling.

LM317T SMD

D2PAK-3: This is a surface-mount device (SMD) package with 3 pins. Suitable for automated assembly processes and use in compact designs where space is a concern. This package type often use in more modern, surface-mount circuit boards.

Each of these packages allows to use the chip in different scenarios based on space, power dissipation needs, and assembly method.

Manufacturer Information

The LM317 T voltage regulator produce by several well-known manufacturers, including:

STMicroelectronics (ST): A leading global semiconductor company that offers the circuit in various package options, widely use in power regulation and general-purpose voltage regulation circuits.

ONSEMI (ON Semiconductor): Another major semiconductor manufacturer, providing the chip with similar specifications and applications, often use in automotive, industrial, and consumer electronics.

Texas Instruments (TI): TI is a prominent supplier of the LM 317T, offering high-quality voltage regulators, including the LM317, for various power management and regulation tasks in consumer, industrial, and communication systems.

Each of these manufacturers offers the LM317T with identical core functionality but differ in packaging, availability, and specific features like lead-free options or temperature ranges. These variations allow designers to choose the most suitable option based on their project needs.

Where and How to Use the LM317?

The IC widely use in various applications requiring adjustable voltage. Some common uses include:

Power Supplies: Ideal for creating variable power supplies with adjustable voltage outputs, from low voltage to 37V.

Battery Charging Circuits: Often use for regulating the charging voltage for lead-acid or lithium-ion batteries.

Constant Current Sources: By connecting a resistor between the adjustment pin and the output, can configure the LM 317T as a current regulator, useful in LED drivers or other current-sensitive applications.

Example Circuit:

For a 12V to 5V conversion, a typical LM317T configuration will include a resistor divider to set the output voltage to 5V. A common value for the resistors in this configuration would be R1 = 240Ω and R2 = 1kΩ.

LM317T Applications

The circuit is a versatile adjustable voltage regulator that widely use in various electronic applications because its ability to provide a stable output voltage across a broad range. Here are some common applications of the LM 317T:

Power Supplies

The device can deliver an adjustable output voltage from 1.2V to 37V, making it ideal for powering a wide range of electronic circuits. Use in both bench power supplies for laboratory testing and portable battery chargers where need a stable, adjustable output.

Battery Charging Circuits

The chip commonly employ in battery chargers, particularly for lead-acid and lithium-ion batteries. The adjustable voltage feature makes it easy to set the charging voltage according to the battery's specifications. It also ensures the voltage remains within the safe range, preventing overcharging and extending battery life.

Constant Current Source

The LM317 T can configure as a constant current source, which is useful for applications such as LED drivers and laser diode circuits. By adding a sense resistor, it can regulate the current flowing through the load, ensuring consistent current despite changes in voltage.

Voltage Regulators for Sensitive Components

For powering sensitive components such as microcontrollers, sensors, and operational amplifiers, the regulator provides a stable and noise-free voltage output. The ability to adjust the output voltage makes it suitable for powering different components from a single source.

Audio Amplifiers

In audio amplifier circuits, often use the chip to provide the necessary regulated voltage for operational amplifiers or as a power supply for audio systems. Its low-noise performance ensures minimal signal distortion, making it ideal for high-fidelity audio applications.

DIY Electronics and Projects

The LM317 frequently use in DIY electronics projects as its ease of use and adjustable output voltage. Hobbyists use it for creating custom power supplies, chargers, and current regulators in their circuits.

Overall, the chip is a flexible and reliable component in electronic designs, offering a broad range of applications in both professional and hobbyist environments.

LM317T Datasheet PDF:

You can download the PDF, which includes all the technical specifications, pinout diagrams, application circuits, and electrical characteristics.

Frequently Asked Questions [FAQ]

What is LM317T price?

The price of the LM317T typically ranges from US$1 to US$3 depending on the supplier and quantity. Bulk purchases can reduce costs, and the price vary by manufacturer, such as Texas Instruments or ONSEMI. Better to check online component suppliers for current pricing and availability.

What is LM317T used for?

The LM317T use as an adjustable voltage regulator in power supplies, battery chargers, LED drivers, and audio amplifiers. It provides a stable output voltage in the range of 1.2V to 37V, making it suitable for powering a wide variety of electronic circuits and components, both in hobbyist and professional applications.

What is the difference between LM317 and LM317T?

Both are electrically identical. The LM317T specifically refers to the TO-220 package, commonly use for higher current and better heat dissipation. The LM317 is a general term for the adjustable voltage regulator, while LM317T is the packaged version typically used in power circuits requiring heat management.

Does the LM317T need a heatsink?

The chip need a heatsink if it’s supplying high current or if the input voltage is significantly higher than the output voltage. Under normal low-current conditions, a heatsink not be necessary, but for high-power applications, adding a heatsink helps dissipate heat and prevent thermal shutdown or damage to the regulator.

What is the voltage range of LM317T?

It provides an adjustable output voltage from 1.2V to 37V. The output voltage determine by an external resistor divider connected to the adjustment pin, giving flexibility in applications. Suitable for powering a wide variety of devices that require a stable, customizable voltage supply within this range.

How does LM317 differ from LM337?

The LM317 is a positive voltage regulator, while the LM337 is a negative voltage regulator. Both are adjustable, but the LM317 use for positive voltage regulation (e.g., 1.2V to 37V), and the LM337 use for negative voltage regulation (e.g., -1.2V to -37V). The pin out and operation are similar, but they regulate opposite polarities.

How does the LM7815 series compare to the LM317 series?

The LM7815 series provides a fixed 15V output, making it ideal for applications needing a constant 15V supply. In contrast, the LM317 series is adjustable, with output voltages ranging from 1.2V to 37V. While the LM7815 is simpler to use for a 15V supply, the LM317 offers more versatility in voltage selection.

What is the difference between LM317T and 7805?

The LM317T is an adjustable voltage regulator capable of providing a wide output range (1.2V to 37V), while the 7805 is a fixed 5V regulator. The LM317T is more versatile, while the 7805 is ideal for circuits that require a stable 5V output. The LM317T also handles a broader range of input voltages.

What kind of capacitor can be used with LM317T?

For the LM317T, recommend a 0.1μF ceramic capacitor on the input for noise filtering. On the output, a 1μF electrolytic or tantalum capacitor improves stability and transient response. Can add 10μF capacitor to the adjustment pin to improve ripple rejection and output stability in sensitive applications.

Conclusion

The LM317T voltage regulator is a powerful, reliable, and flexible voltage regulator use in a wide variety of applications. Its adjustable output, ease of use, and built-in protections make it a popular choice in electronics. Whether you're building a custom power supply, designing a battery charger, or creating a precision current regulator, the LM317T offers the versatility and performance needed to get the job done efficiently and safely.

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