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STMicroelectronics LM317T-DG
- Part No.:
- LM317T-DG
- Manufacturer:
- STMicroelectronics
- Package:
- TO-220-3
- Datasheet:
-
LM317T-DG.pdf
- Description:
- IC REG LIN POS ADJ 1.5A TO220-3
- Quantity:
- Payment:
- Shipping:
Inventory:6,617
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Product details
Overview
LM317T-DG from STMicroelectronics is a monolithic adjustable positive voltage regulator in TO-220 (dual-gauge) package, delivering 1.5 A output current with 1.2 V to 37 V adjustable output range, 0.1% line and load regulation, and integrated thermal shutdown, current limiting, and safe operating area (SOA) protection. It serves as the core voltage-setting element in lab power supplies, battery chargers, and industrial DC power rails where precision, stability, and robustness are required.
For engineers reviewing the LM317T-DG datasheet, LM317T-DG pinout, LM317T-DG application, or LM317T-DG equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation guidance, and confirmed alternative options for voltage regulation circuits requiring ±1.5% output accuracy and ≥1.5 A continuous current capability.
Technical Context
The LM317T-DG operates as a floating three-terminal linear regulator: its reference voltage (1.25 V nominal) is maintained between OUTPUT and ADJUST pins, enabling output voltage setting via external resistive divider (VO = 1.25 V × (1 + R₂/R₁) + IADJR₂). It uses internal bandgap reference and error amplifier with series pass transistor to regulate output against input variation and load transients.
Its architecture supports high-voltage floating operation-only the input-to-output differential voltage (max 40 V) matters-not absolute input voltage-making it suitable for high-side regulation in systems up to 60 V total rail. Protection circuitry actively monitors junction temperature, output current, and SOA to disable conduction before damage occurs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 1.2 V to 37 V - set by external resistor divider; enables single BOM part to replace multiple fixed-output regulators. |
| Output Current | ≥1.5 A continuous - sufficient for powering analog subsystems, microcontroller boards, and LED drivers without external boost stages. |
| Reference Voltage | 1.25 V (±1%) - stable internal bandgap reference forms basis for precise output scaling; low drift ensures <1% tempco over -40°C to +125°C. |
| Line Regulation | 0.04 %/V max - limits output shift to ≤15 mV per 10 V input change at 500 mA load, critical for unregulated input sources. |
| Load Regulation | 25 mV max (VO ≤ 5 V), 0.5% max (VO ≥ 5 V) - maintains tight output under full-load step changes, essential for sensitive analog loads. |
| Adjust Pin Current | 50–100 µA - low and stable bias current minimizes error term (IADJR₂) in output equation; simplifies divider design. |
| Thermal Shutdown Threshold | 125°C junction - self-protects during overload or poor heatsinking; resumes regulation after cooldown without latch-up. |
Pinout & Package
LM317T-DG uses TO-220 dual-gauge package (JEDEC TO-220AB variant), with metal tab electrically connected to OUTPUT pin and optimized for vertical mounting with heatsink interface. Thermal resistance junction-to-case is 5 °C/W, enabling >1.5 A operation with modest heatsinking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INPUT (Pin 1) | Unregulated DC input supply connection | Must be ≥2.5 V above desired output; max 40 V differential vs OUTPUT; requires local 0.1 µF bypass capacitor. |
| OUTPUT (Pin 2) | Regulated DC output node | Delivers load current; metal tab is internally bonded to this pin-must be isolated from chassis ground unless output is ground-referenced. |
| ADJUST (Pin 3) | Feedback reference node | Connected to resistor divider midpoint; senses 1.25 V reference; 10 µF capacitor to ground improves ripple rejection by 15 dB. |
Key Features
| Feature | Design Value |
|---|---|
| Floating regulator architecture | Operates with input up to 40 V above output-enables high-side regulation in 60 V systems without level-shifting circuitry. |
| Integrated SOA protection | Prevents destruction during short-circuit or thermal runaway by dynamically limiting power dissipation in real time. |
| Low adjustment pin current | ≤100 µA with ±5 µA variation across line/load-reduces divider error and allows use of high-value resistors for low quiescent current. |
| Remote sensing support | Ground terminal of R₂ placed near load ground-compensates for PCB trace IR drop, improving regulation accuracy at point-of-load. |
| Programmable current regulation | Configurable as constant-current source (IO ≈ 1.25 V / R₁) - used in LED drivers and battery charge control without added ICs. |
Applications
| Lab Bench Power Supply | Battery Charger (12 V Lead-Acid) |
|---|---|
|
Use Scenario: Adjustable 0–30 V, 0–1.5 A bench supply with coarse/fine voltage control and current limiting. IC Role / Device Role / Timing Role: Primary voltage-setting regulator; implements output adjust via potentiometer divider and current limit via sense resistor. Use Value: Eliminates need for multiple fixed regulators; 0.1% regulation ensures stable voltage during load sweeps; thermal shutdown prevents overheating during current-limit testing. |
Use Scenario: Constant-voltage/constant-current charger for sealed lead-acid batteries with float voltage control and overcharge protection. IC Role / Device Role / Timing Role: Regulates bulk charge voltage (14.4 V) and transitions to float (13.8 V); current limit set via R₁ controls initial charge rate. Use Value: Programmable output avoids dedicated charger ICs; SOA protection prevents damage during battery short or reverse connection; low dropout enables use with low-headroom wall adapters. |
| Industrial Sensor Signal Conditioning | Programmable Analog Front-End |
|
Use Scenario: Clean, low-noise ±15 V dual supply for op-amp-based sensor amplifiers in PLC I/O modules. IC Role / Device Role / Timing Role: Positive rail regulator (with LM337 for negative rail); filters input ripple and rejects line noise via CADJ capacitor. Use Value: 0.003% output noise and 80 dB SVR with 10 µF CADJ ensure <10 µV RMS noise on 15 V rail-critical for 16-bit ADC reference stability. |
Use Scenario: Configurable voltage source for calibration, DAC output buffering, or test equipment stimulus generation. IC Role / Device Role / Timing Role: Digitally selected output using rotary switch + resistor ladder on ADJUST node; enables 5 discrete outputs from one footprint. Use Value: Reduces BOM count and PCB area vs multiple LDOs; 1.25 V reference tolerance ensures ±1.5% absolute accuracy across all settings without trimming. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable linear voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM317T (TO-220 single-gauge) | Identical electrical specs; same thermal resistance (5 °C/W) but single-gauge tab lacks dual mounting holes. | Suitable for standard heatsink clips; less mechanical rigidity in high-vibration environments. | Select when mechanical mounting matches legacy TO-220AB footprints and vibration is not a concern. |
| LM317K (TO-3 metal can) | Higher thermal resistance (2.5 °C/W junction-to-case), wider temp range (−55°C to +150°C), higher price. | Used in military/aerospace where extended temperature and hermetic sealing are mandatory. | Choose only if extended temperature rating or MIL-STD-883 compliance is required; otherwise LM317T-DG offers better cost/performance. |
Compared with LM317T-DG, the LM317T offers identical regulation performance with simplified mounting, while LM317K trades cost and size for extreme environmental resilience-neither provides improved electrical specs, making LM317T-DG the optimal balance of manufacturability, thermal performance, and industrial reliability.
Availability
LM317T-DG is available at Aetrix Electronics and suitable for lab power supplies, battery chargers, industrial sensor signal conditioning, and programmable analog front-ends requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM317T-DG includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.
The LM317 series belongs to ST's legacy linear regulator product line, engineered specifically for high-reliability, low-cost, adjustable DC power conversion in industrial and instrumentation applications where simplicity, ruggedness, and field-proven stability are paramount.
FAQ
What is the minimum load current required for stable regulation with LM317T-DG?
The LM317T-DG requires a minimum load current of 3.5 mA (typical) to 10 mA (max) to maintain regulation. This is due to internal quiescent current being returned to the output pin. If load current falls below this threshold-such as in light-load or standby conditions-the output voltage may rise above the set value. A 240 Ω resistor from OUTPUT to ADJUST provides exactly 5.2 mA, satisfying this requirement across the full output range.
Can LM317T-DG be used in a negative voltage configuration?
No-LM317T-DG is a positive adjustable regulator only and cannot regulate negative voltages. For symmetric dual-rail supplies, pair it with the complementary LM337T-DG (negative adjustable regulator). Attempting to invert LM317T-DG by grounding the OUTPUT pin violates absolute maximum ratings and risks device failure due to reverse biasing of internal junctions.
How does the ADJUST pin capacitor (CADJ) improve performance?
A 10 µF capacitor from ADJUST to ground (CADJ) improves ripple rejection by ~15 dB at 120 Hz, reducing output AC content caused by rectified input. It also enhances transient response by stabilizing the feedback node during fast load steps. ST recommends tantalum or aluminum electrolytic types; ceramic capacitors are unsuitable due to insufficient ESR, which may cause instability in the internal error amplifier loop.
Is LM317T-DG pin-compatible with older LM317 variants from other manufacturers?
Yes-LM317T-DG maintains JEDEC-standard TO-220 pinout (INPUT–OUTPUT–ADJUST) and electrical specifications consistent with industry-standard LM317 devices from Texas Instruments, ON Semiconductor, and Diodes Inc. However, ST's version features tighter line/load regulation (0.04 %/V and 25 mV) and enhanced SOA protection, offering superior robustness in demanding industrial environments without layout changes.
LM317T-DG Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-220-3
- Packaging:
- Tube
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.2V
- Voltage - Output (Max):
- 37V
- Voltage Dropout (Max):
- -
- Current - Output:
- 1.5A
- Current - Quiescent (Iq):
- 10 mA
- Current - Supply (Max):
- -
- PSRR:
- 80dB ~ 65dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature, Short Circuit
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220
LM317T-DG FAQ
1.How can I place an order for LM317T-DG through Aetrix?
Please submit a Request for Quotation (RFQ) for LM317T-DG on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM317T-DG reliable?
The price and inventory of LM317T-DG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317T-DG is usually 5 days.
3.What payment methods are accepted for LM317T-DG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317T-DG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM317T-DG?
LM317T-DG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM317T-DG order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM317T-DG?
For technical support, including LM317T-DG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317T-DG requirements.
6.How does Aetrix verify that LM317T-DG is sourced from the original manufacturer or authorized distributors?
All LM317T-DG products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM317T-DG meets industry standards.
7.What is the process for return or replacement of LM317T-DG?
All LM317T-DG units undergo pre-shipment inspection (PSI). If there is an issue with LM317T-DG, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM317T-DG part is unused and in its original packaging.
Return procedure for LM317T-DG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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