LM317T - 1.5A Adjustable Positive Voltage Regulator | STMicroelectronics
MPN: LM317T ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.72 | $7.20 |
| 100 | $0.58 | $58.00 |
| 500 | $0.49 | $245.00 |
| 1,000 | $0.42 | $420.00 |
Drop-in alternatives for LM317T — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
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LM317T
✅ Drop-In✓ 99,999 In Stock
$0.42 / Unit
View Datasheet →LM317T
✅ Drop-In✓ 99,999 In Stock
$0.42 / Unit
View Datasheet →LM317T
✅ Drop-In✓ 99,999 In Stock
$0.42 / Unit
View Datasheet →LM317T Maximum Ratings & Electrical Characteristics
| Output Type | Adjustable |
| Output Voltage Range | 1.2 V to 37 V |
| Maximum Output Current | 1.5 A |
| Input Voltage Range | 4.2 V to 40 V |
| Dropout Voltage | 2 V typical at 1.5 A |
| Reference Voltage | 1.25 V |
| Line Regulation | 0.01%/V typical |
| Load Regulation | 0.1% typical |
| Quiescent Current | 5 mA typical |
| Operating Temperature | 0C to +125C |
| Package | TO-220 |
| Mounting Type | Through Hole |
| Thermal Resistance (Junction-to-Case) | 5 C/W |
| RoHS Status | Compliant |
| Protection Features | Current limiting, thermal overload, safe area compensation |
LM317T Pin Configuration
| Pin 1 | Input — Unregulated input voltage |
| Pin 2 | Output — Regulated output voltage |
| Pin 3 | Adjustment — Adjustment pin for setting output voltage |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
LM317T is suitable for 6 applications: Adjustable Power Supply, Battery Charger, Constant Current Source, Audio Circuit Power Supply, Instrumentation and Test Equipment, Industrial Control Systems.
Adjustable Power Supply
The LM317T is widely used in bench power supplies and adjustable voltage sources. Its output voltage can be set from 1.2V to 37V using two external resistors, making it ideal for prototyping and testing. The device's 1.5A output current and 0.1% load regulation ensure stable voltage under varying loads. In a typical bench supply, the LM317T is paired with a transformer, rectifier, and filter capacitor to produce a clean DC output. The adjustment pin is connected to a potentiometer for easy voltage adjustment. The LM317T's internal current limiting and thermal protection safeguard the supply and the load. For higher currents, multiple LM317T devices can be paralleled with ballast resistors, though this is less common. The low noise and simplicity of the LM317T make it a preferred choice for hobbyist and educational power supplies.
Recommended
Battery Charger
The LM317T can be configured as a constant current source for battery charging. By placing a resistor between the output and adjustment pins, the charging current is set to I = 1.25V / R. For example, a 1.25-ohm resistor sets a 1A charging current. The LM317T's low dropout voltage of 2V allows it to charge batteries from a slightly higher supply voltage. In a typical charger, the LM317T is connected to a DC source, and the battery is placed in series with the current-setting resistor. The device's thermal shutdown protects against overheating during prolonged charging. However, the LM317T lacks the sophisticated charging algorithms of dedicated charger ICs, so it is best suited for simple lead-acid or NiMH batteries. For Li-ion batteries, a dedicated charger IC with voltage and current regulation is recommended.
Recommended
Constant Current Source
The LM317T excels as a constant current source for LED drivers, sensor excitation, and current limiting. The output current is precisely set by a single resistor, with a typical accuracy of 1%. For example, a 12.5-ohm resistor sets a 100mA current. The LM317T's wide input voltage range (up to 40V) allows it to drive loads with varying resistance while maintaining a constant current. In LED lighting applications, the LM317T ensures uniform brightness by providing a stable current to each LED string. The device's thermal protection prevents damage from short circuits or excessive load. However, the power dissipation in the LM317T can be significant when the load voltage is low, so a heatsink is often required. For high-power LED arrays, a switching LED driver is more efficient.
Recommended
Audio Circuit Power Supply
The LM317T is used in audio circuits to provide a clean, low-noise power rail for op-amps, preamplifiers, and DACs. Its linear regulation eliminates switching noise, which is critical for high-fidelity audio. The output voltage can be set to match the required rail voltage, such as 12V or 15V. In a typical audio supply, the LM317T is preceded by a rectifier and filter capacitor, and the output is bypassed with a 10uF capacitor to improve transient response. The LM317T's 0.01%/V line regulation ensures stable voltage even with mains fluctuations. However, its noise performance (typically 40uVrms) is higher than dedicated low-noise LDOs, so for ultra-low-noise applications, a dedicated regulator like the TPS7A4701 is preferred. The LM317T remains a cost-effective choice for general audio power supplies.
Recommended
Instrumentation and Test Equipment
The LM317T is commonly used in instrumentation and test equipment as a precision voltage reference or local regulator. Its adjustable output and 0.1% load regulation make it suitable for calibrating and testing circuits. In a bench multimeter or oscilloscope, the LM317T can provide a stable reference voltage for ADC circuits. The device's wide temperature range (0C to +125C) ensures reliable operation in various environments. The TO-220 package allows for easy mounting on a heatsink or PCB. The LM317T's simplicity and low cost make it a popular choice for educational labs and DIY test equipment. For higher precision, a dedicated voltage reference IC like the REF102 is recommended.
Recommended
Industrial Control Systems
The LM317T is used in industrial control systems to provide regulated supply voltages for sensors, microcontrollers, and communication interfaces. Its robust protection features, including current limiting and thermal shutdown, ensure reliable operation in harsh environments. The output voltage can be set to 3.3V, 5V, or other standard levels using external resistors. In a typical industrial application, the LM317T is powered from a 24V bus and steps down to a lower voltage for logic circuits. The device's wide input range (up to 40V) accommodates voltage fluctuations common in industrial settings. The TO-220 package can be bolted to a chassis for heat dissipation. For higher efficiency, a switching regulator is preferred, but the LM317T's simplicity and low noise make it suitable for noise-sensitive analog circuits.
Recommended
Recommended Products Summary
Engineering reference data for LM317T — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM317T (TI) | LM317T (onsemi) | LM317T (Diodes Inc) |
|---|---|---|---|---|
| Package | TO-220 | TO-220 | TO-220 | TO-220 |
| Output Current | 1.5 A | 1.5 A | 1.5 A | 1.5 A |
| Output Voltage Range | 1.2V to 37V | 1.2V to 37V | 1.2V to 37V | 1.2V to 37V |
| Dropout Voltage | 2V typical | 2V typical | 2V typical | 2V typical |
| Line Regulation | 0.01%/V | 0.01%/V | 0.01%/V | 0.01%/V |
| Load Regulation | 0.1% | 0.1% | 0.1% | 0.1% |
| Operating Temperature | 0C to +125C | 0C to +125C | 0C to +125C | 0C to +125C |
| RoHS Status | Compliant | Compliant | Compliant | Compliant |
Key Differentiators
- Widely available from multiple manufacturers (vs LM317T (TI))
- TO-220 package for easy heatsinking (vs LM317 (SO-8))
- Proven reliability and long lifecycle (vs Newer LDOs)
Design Notes
The LM317T in TO-220 package has a junction-to-case thermal resistance of 5 C/W. For power dissipation above 2W, a heatsink is required. For example, at VIN=12V, VOUT=5V, and 1A load, power dissipation is 7W, so a heatsink with a thermal resistance of 10 C/W or better is recommended to keep the junction temperature below 125C.
Place input and output capacitors close to the LM317T pins. A 0.1uF capacitor on the input and a 1uF tantalum or electrolytic capacitor on the output are recommended for stability. For improved ripple rejection, add a 10uF capacitor between the adjustment pin and ground. Use a heatsink tab connected to the PCB ground plane for better thermal performance.
Do not exceed the maximum input-to-output differential of 40V. Ensure the adjustment pin is not left floating; always connect it to a resistor divider. When using large output capacitors, add protection diodes (1N4007) from output to input and from adjustment to output to prevent discharge through the regulator during input short circuits.
Compliance Information
RoHS compliant per STMicroelectronics product page. Not AEC-Q100 qualified. Halogen-free status not specified in the provided data.
