The LM317T is an adjustable 3-terminal positive voltage regulator capable of delivering more than 1.5 A across an output voltage range of 1.2 V to 37 V. It is remarkably easy to use, requiring only two external resistors to set the desired output voltage. Designed with internal current limiting, thermal shutdown, and safe area compensation, the LM317T offers robust protection features, making it highly reliable and resistant to damage under fault conditions.
The LM317T is highly versatile and widely used in applications such as local and on-card voltage regulation. It can be configured as a programmable output regulator or, by connecting a fixed resistor between the adjustment and output terminals, as a precision current regulator.
INPUT: Connects to the unregulated voltage source and supplies power to the internal regulator.
OUTPUT: Provides the regulated output voltage; the value is set using external resistors.
ADJUST: Adjustment pin used with resistors to set and fine-tune the output voltage.
| Parameter | Specification |
| Part Status | Active |
| Output Voltage Range | 1.2 V ~ 37 V |
| Output Current | 1.5 A |
| Input-Output Voltage Differential | 3 V ~ 40 V |
| Line Regulation | 0.01% / V |
| Quiescent Current | 10 mA |
| Reference Voltage | 1.25 V |
| PSRR | 80dB ~ 65dB (120Hz) |
| Operating Temperature Range | 0°C ~ 125°C |
| Package Type | TO-220-3 |
Output Current in Excess of 1.5 A
Output Adjustable between 1.2 V and 37 V
Internal Thermal Overload Protection
Internal Short Circuit Current Limiting Constant with Temperature
Output Transistor Safe−Area Compensation
Floating Operation for High Voltage Applications
Eliminates Stocking with many Fixed Voltages
Available in Surface Mount D2PAK−3, and Standard 3−Lead Transistor Package
NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable
These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant
Adjustable voltage regulators
Precision current regulators
Battery chargers
Power supply for operational amplifiers
Local, on-card voltage regulation
Programmable output regulation
LED drivers
Post regulators for switching power supplies
Current-limited power supplies
Microcontroller and logic circuit power sources
Common equivalents for the LM317T include LM317, LM317L, LM317HV, LM338, LM350, and UA7815. Their parameters and applications are all similar to LM317T.
The LM317T uses the TO-220-3 package, a common three-lead through-hole package known for its excellent heat dissipation and mechanical strength. The package has a moderate size, making it easy to mount onto a heatsink to improve current output capability and thermal stability. The typical lead pitch of the TO-220-3 package is 2.54 mm, with a simple pin layout consisting of Input, Output, and Adjust terminals.
When connecting the LM317T, first correctly identify its three pins: Input, Output, and Adjust. Connect the desired stabilized DC input voltage to the Input pin, and connect the stabilized output to the Output pin. To set the output voltage, place a resistor (R1) between the Adjust and Output pins, and another resistor (R2) between the Adjust pin and ground. By adjusting the ratio of R1 to R2, the desired output voltage can be configured.
For enhanced stability, it is recommended to add a 0.1μF capacitor between the Input pin and ground, and a capacitor of at least 1μF between the Output pin and ground to filter out high-frequency noise. Throughout the connection process, ensure the device and circuit are powered off during installation, and properly attach a heatsink to maintain good thermal performance.
The LM317T is an adjustable 3-terminal voltage regulator capable of providing a stable output voltage ranging from 1.2V to 37V, with a maximum output current of 1.5A.
The LM317T uses external resistors to set the output voltage. It regulates the voltage by adjusting the resistance between the Adjust pin and the output.
Yes, by using a fixed resistor between the Adjust and Output pins, the LM317T can function as a precision current regulator.
The LM317T features built-in current limiting, thermal shutdown, and safe-area compensation to prevent damage to the device.
