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STMicroelectronics LM317D2T-TR
- Part No.:
- LM317D2T-TR
- Manufacturer:
- STMicroelectronics
- Package:
- TO-263-3, D2PAK (2 Leads + Tab), TO-263AB
- Datasheet:
-
LM317D2T-TR.pdf
- Description:
- IC REG LINEAR POS ADJ 1.5A D2PAK
- Quantity:
- Payment:
- Shipping:
Inventory:35,996
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Product details
Overview
LM317D2T-TR from STMicroelectronics is a monolithic adjustable positive voltage regulator in D²PAK package, delivering over 1.5 A output current with 1.2 V to 37 V adjustable output range, 0.1% line and load regulation, and integrated current limiting, thermal shutdown, and SOA protection - used in industrial power supplies, battery chargers, and lab bench supplies.
For engineers reviewing the LM317D2T-TR datasheet, LM317D2T-TR pinout, LM317D2T-TR application, or LM317D2T-TR equivalent, key selection considerations include input-output differential voltage (max 40 V), minimum load current (3.5–10 mA), reference voltage accuracy (1.2–1.3 V), thermal resistance junction-to-ambient (62.5 °C/W), and adjustment pin current (50–100 µA).
Technical Context
The LM317D2T-TR operates as a floating three-terminal regulator, sensing only the differential voltage between input and output pins - enabling high-voltage floating applications without ground-referenced constraints. Its internal 1.25 V bandgap reference (VREF) sets output via external resistor divider, with IADJ ≤ 100 µA minimizing error contribution.
It implements full protection: foldback current limiting activates before thermal shutdown, while safe operating area (SOA) control prevents secondary breakdown during transient overload. The device requires no external components for basic operation but benefits from CADJ = 10 µF (adjust-to-ground) to improve ripple rejection by 15 dB.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output voltage range | 1.2 V to 37 V - set by external R1/R2 divider; enables single BOM for multiple output rails |
| Output current | ≥1.5 A continuous - supports high-current analog/industrial loads without external pass transistors |
| Line regulation | 0.01–0.07 %/V - maintains stable output despite ±10% AC line variation or unregulated DC input drift |
| Load regulation | 5–70 mV or 0.1–1.5 % - ensures <±1% output deviation across full 10 mA–1.5 A load range |
| VREF (ref voltage) | 1.2–1.3 V (typ. 1.25 V) - precise internal reference enables ±1% initial output accuracy with standard resistors |
| Input-output differential max | 40 V - defines maximum allowable VIN–VOUT; critical for dropout and thermal design |
| Thermal resistance (RthJA) | 62.5 °C/W - D²PAK package allows ~3 W dissipation at 25°C ambient without heatsink |
Pinout & Package
D²PAK (SMD 2L STD-ST) package: surface-mount, 3-pin, isolated tab (connected to output), thermally enhanced for PCB copper pour mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (INPUT) | Unregulated input supply connection | Must be ≥1.25 V above desired output; max VI–VO = 40 V limits usable input range |
| Pin 2 (OUTPUT) | Regulated output and thermal pad connection | Tab is electrically tied to OUTPUT - requires isolation from chassis ground if floating operation used |
| Pin 3 (ADJUST) | Reference feedback node | Senses 1.25 V above OUTPUT; sets VO via R1–R2 divider; draws 50–100 µA quiescent current |
Key Features
| Feature | Design Value |
|---|---|
| Floating operation capability | Enables high-side regulation (e.g., 100 V rail) as long as VI–VO ≤ 40 V - no ground-referenced constraint |
| Integrated SOA protection | Prevents second breakdown during short-circuit or capacitive load discharge - eliminates need for external current-sense resistor |
| Low IADJ drift | IADJ variation ≤5 µA over VI–VO = 2.5–40 V and IO = 10 mA–500 mA - minimizes R2-induced output error |
| High SVR with CADJ | Supply rejection improves from 65 dB (no CADJ) to 80 dB (with 10 µF on ADJ-to-ground) - critical for noisy input sources |
| Remote sensing support | R1 placed near regulator + R2 ground near load enables millivolt-level load regulation compensation |
Applications
| Industrial Power Supply | Battery Charger |
|---|---|
Use Scenario: Programmable 24 V/1.5 A bench supply with coarse/fine voltage control. IC Role / Device Role / Timing Role: Primary adjustable linear regulator; sets output via potentiometer-based R1/R2 divider. Use Value: Eliminates need for multiple fixed regulators; 0.1% regulation ensures stable bias for op-amps and ADC references. | Use Scenario: 12 V sealed lead-acid battery charger with constant-voltage/constant-current transition. IC Role / Device Role / Timing Role: Voltage-controlled current source using ADJ pin feedback and series sense resistor. Use Value: Achieves ±1% charge voltage accuracy (14.4 V) and programmable 0.6 A peak current via R1 - meets SLA spec without microcontroller. |
| Laboratory Instrumentation | LED Constant-Current Driver |
Use Scenario: Low-noise 5 V/1 A supply for spectrum analyzer front-end analog circuitry. IC Role / Device Role / Timing Role: Post-regulator after switching pre-converter; filters switching noise via CADJ and output capacitor. Use Value: 0.003% output noise (10 Hz–100 kHz) preserves signal integrity; 80 dB SVR suppresses 120 Hz ripple from rectified AC. | Use Scenario: High-brightness LED string driver (3× white LEDs, 9.6 V, 350 mA) in signage application. IC Role / Device Role / Timing Role: Precision current regulator configured with R1 between ADJ and OUTPUT. Use Value: Delivers stable 350 mA ±2% over 10–40°C ambient - avoids LED color shift and thermal runaway without sensing IC. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM317T | TO-220 package; RthJA = 50 °C/W; same electrical specs | Requires through-hole PCB layout and mechanical heatsink mounting | Select when board assembly uses through-hole process or higher thermal mass heatsinking is available |
| TLV1117-33CDCY | Fixed 3.3 V output; max 800 mA; dropout = 1.2 V; SOT-223 | Not adjustable; unsuitable for variable-output or >1 A applications | Select only for low-dropout, fixed-voltage, space-constrained designs where 3.3 V suffices |
Compared with LM317T, the LM317D2T-TR offers superior thermal performance in SMT layouts with copper pour, while TLV1117-33CDCY trades adjustability and current capacity for ultra-low dropout and footprint - making it incompatible for variable-output or high-current use cases.
Availability
LM317D2T-TR is available at Aetrix Electronics and suitable for industrial power supplies, battery charging systems, laboratory instrumentation, and LED driver circuits requiring stable component supply, long-term lifecycle continuity, and RoHS-compliant sourcing.
Supply support for LM317D2T-TR 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, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.
The LM317 product line delivers robust, pin-compatible adjustable linear regulators optimized for reliability in harsh environments - targeting industrial control, test equipment, and legacy-compatible power designs where simplicity and ruggedness outweigh switching efficiency.
FAQ
What is the minimum load current required for stable regulation?
The LM317D2T-TR requires a minimum load current of 3.5 mA (typ.) to 10 mA (max.) to maintain regulation. This is due to internal quiescent current returning to the output pin; insufficient load causes output voltage to rise uncontrollably. A 120 Ω resistor from OUTPUT to GND satisfies this requirement for 12 V outputs.
Can the LM317D2T-TR be used in floating high-voltage configurations?
Yes - the LM317D2T-TR operates as a floating regulator, referencing only the voltage difference between INPUT and OUTPUT pins. As long as VI–VO ≤ 40 V, it can regulate outputs at 100 V, 200 V, or higher above ground - commonly used in telecom line cards and HV bias supplies.
How does the ADJUST pin current affect output accuracy?
IADJ (50–100 µA) flows through R2 in the feedback divider, adding an error term of IADJ × R2 to the output voltage. For R2 = 2.4 kΩ, this contributes up to 240 mV error - mitigated by selecting R1/R2 values that keep R2 ≤ 240 Ω or using the LM317B variant with tighter IADJ tolerance.
What thermal derating applies when using the D²PAK package without a heatsink?
With RthJA = 62.5 °C/W and max TJ = 125 °C, the LM317D2T-TR dissipates ≤3.0 W at 25°C ambient without heatsink (P = (125–25)/62.5). At 70°C ambient, max dissipation drops to 1.76 W - corresponding to ~1.2 A at 3 V dropout. PCB copper area directly under the tab is essential for achieving rated RthJA.
LM317D2T-TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-263-3, D2PAK (2 Leads + Tab), TO-263AB
- Packaging:
- Tape & Reel (TR)
- 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:
- Surface Mount
- Supplier Device Package:
- D2PAK
LM317D2T-TR FAQ
1.How can I place an order for LM317D2T-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for LM317D2T-TR 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 LM317D2T-TR reliable?
The price and inventory of LM317D2T-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317D2T-TR is usually 5 days.
3.What payment methods are accepted for LM317D2T-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317D2T-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM317D2T-TR?
LM317D2T-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM317D2T-TR 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 LM317D2T-TR?
For technical support, including LM317D2T-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317D2T-TR requirements.
6.How does Aetrix verify that LM317D2T-TR is sourced from the original manufacturer or authorized distributors?
All LM317D2T-TR 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 LM317D2T-TR meets industry standards.
7.What is the process for return or replacement of LM317D2T-TR?
All LM317D2T-TR units undergo pre-shipment inspection (PSI). If there is an issue with LM317D2T-TR, 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 LM317D2T-TR part is unused and in its original packaging.
Return procedure for LM317D2T-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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