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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

STMicroelectronics LM317D2T

Name: LM317D2T
Brand: STMicroelectronics
SKU: LM317D2T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LM317D2T

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Package:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Datasheet:: LM317D2T.pdf

Description:: IC REG LINEAR POS ADJ 1.5A D2PAK

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Inventory:2,900

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Product details

Overview

LM317D2T from STMicroelectronics is a monolithic adjustable positive voltage regulator in D2PAK (TO-263) package, delivering 1.5A output current with 1.2V to 37V adjustable output voltage, 0.01% typical line regulation, and integrated thermal shutdown, current limiting, and safe operating area (SOA) protection. It is used in lab power supplies, battery chargers, and programmable DC sources where precision, stability, and high-voltage floating operation are required.

For engineers reviewing the LM317D2T datasheet, LM317D2T pinout, LM317D2T application, or LM317D2T equivalent, key selection criteria include output voltage adjustability via two-resistor divider, minimum load current requirement (3.5 mA), reference voltage tolerance (1.20–1.30 V), and thermal resistance (R_thj-amb = 62.5°C/W in D2PAK).

Technical Context

The LM317D2T operates as a floating three-terminal regulator, sensing only the differential voltage between input and output pins - enabling high-side or floating configurations up to 40V differential. Its internal 1.25V bandgap reference sets output via external R1/R2 divider, with adjustment pin current ≤100 µA and negligible temperature drift (±1% over junction temperature range).

It implements analog current limiting with foldback characteristics, SOA-controlled pass transistor drive, and thermal shutdown triggered at T_j ≥ 125°C (LM317 grade). Load regulation remains ≤0.5% for V_O ≥5V across 10mA–1.5A, and ripple rejection reaches 80dB with 10µF capacitor on the ADJ pin.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage Range	1.2 V to 37 V - set externally by resistor divider; enables single BOM part for multiple output rails.
Max Output Current	1.5 A continuous - limited by thermal dissipation in D2PAK; derates above 25°C ambient per R_thj-amb = 62.5°C/W.
Reference Voltage	1.25 V (typ), 1.20–1.30 V (min/max) - defines accuracy baseline for all output settings; stable over temperature and line.
Line Regulation	0.01–0.07 %/V - ensures <±0.37 mV/V change in output under input variation; critical for unregulated DC inputs.
Load Regulation	5–70 mV (for V_O ≤5V), 0.1–1.5 % (for V_O ≥5V) - maintains tight output under full-load transients.
Adjust Pin Current	50–100 µA - low and stable, minimizing error term (I_ADJ·R2) in output equation; simplifies design of high-R divider networks.
Thermal Shutdown Threshold	125°C junction - protects against sustained overload or inadequate heatsinking; auto-recovery after cooldown.

Pinout & Package

LM317D2T uses the D2PAK (TO-263) surface-mount package with exposed thermal pad (pin 2 connected to output). The package measures 15.0–15.85 mm length, 9.0–9.3 mm width, and 4.88–5.28 mm height, rated for 62.5°C/W junction-to-ambient thermal resistance.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (ADJ)	Adjustment Reference Input	Connects to voltage divider midpoint; senses 1.25V reference relative to output; requires low-impedance path to ground for stability.
Pin 2 (OUT)	Regulated Output Terminal	Delivers regulated voltage; also serves as return path for quiescent current; must be tied directly to load ground for remote sensing.
Pin 3 (IN)	Unregulated Input Terminal	Accepts input 2.5–40V above output; requires ≥0.1 µF ceramic bypass close to pin to suppress HF noise and prevent oscillation.

Key Features

Feature	Design Value
Floating regulator architecture	Supports high-side, battery-ground-referenced, or negative-output (with inverted configuration) topologies without level-shifting circuitry.
Integrated protection suite	Combines current limiting, thermal shutdown, and SOA control - eliminates need for external foldback or thermal sensors in most designs.
Low I_ADJ drift	≤5 µA variation over full line/load/temperature range - ensures predictable output error and simplifies precision applications.
Programmable current regulation	Configurable as constant-current source (e.g., LED driver or battery charger) using single resistor from ADJ to load return.
High ripple rejection	80 dB with 10 µF ADJ-to-ground capacitor - reduces AC line noise impact on output without requiring large LC filters.

Applications

Lab Bench Power Supply

Battery Charger (12V Lead-Acid)

Use Scenario: Adjustable bench supply delivering 3–24V at up to 1.5A for prototype validation and IC testing.

IC Role / Device Role / Timing Role: Primary voltage regulation and current limiting element; configured with potentiometer and fixed resistors for coarse/fine adjustment.

Use Value: Eliminates need for multiple fixed regulators; ±0.5% output stability supports analog circuit characterization and sensor biasing.

Use Scenario: Constant-voltage/constant-current 12V lead-acid battery charger with float mode and thermal foldback.

IC Role / Device Role / Timing Role: Regulator core implementing CV/CC transition via sense resistor and ADJ pin feedback network.

Use Value: Enables precise 14.4V absorption and 13.6V float voltages with automatic current taper below 100mA - prevents overcharge.

Programmable DC Source (Digital Control)

Industrial Sensor Excitation

Use Scenario: Microcontroller-driven DC source with DAC-controlled output voltage (e.g., 0–30V) for automated test equipment.

IC Role / Device Role / Timing Role: Analog regulation stage receiving DAC-adjusted reference voltage at ADJ pin; provides low-noise, high-PSRR output.

Use Value: Delivers <100 µV RMS noise and 65–80 dB PSRR - meets requirements for calibration-grade signal sourcing.

Use Scenario: Precision 5V or 10V excitation for strain gauges, RTDs, and bridge sensors in industrial PLC modules.

IC Role / Device Role / Timing Role: Low-drift, low-noise voltage reference generator; output stabilized with 1 µF tantalum capacitor and remote ground sensing.

Use Value: Maintains <0.01%/°C output drift and <50 ppm load regulation - ensures sub-0.1% measurement accuracy in 4–20mA loops.

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)	Different package (TO-220 vs. D2PAK); higher R_thj-amb = 50°C/W; identical electrical specs and pinout.	Suitable for through-hole prototyping or lower-power (<1A) applications with adequate heatsinking.	Select when manual assembly, breadboarding, or legacy board compatibility is prioritized over thermal performance or SMT volume production.
TLV1117-33CDR (TI)	Fixed 3.3V output; max 800mA; dropout voltage ~1.2V; no ADJ pin; different pinout and protection features.	Limited to low-voltage, low-dropout applications; not adjustable; lacks SOA control and thermal foldback.	Choose only for cost-sensitive, fixed-output, low-power embedded rails where adjustability and robustness are unnecessary.

Compared with LM317T and TLV1117-33CDR, the LM317D2T uniquely balances SMT manufacturability, 1.5A capability, full adjustability, and comprehensive protection - making it optimal for production-grade, thermally constrained, and programmable power designs.

Availability

LM317D2T is available at Aetrix Electronics and suitable for lab power supplies, battery charging systems, and industrial sensor excitation circuits requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LM317D2T 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, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.

The LM317 series belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-cost, high-reliability adjustable DC power conversion in non-switching applications demanding simplicity and fault resilience.

FAQ

What is the minimum load current required for stable regulation with LM317D2T?

The LM317D2T requires a minimum load current of 3.5 mA (typical) to maintain regulation, due to internal quiescent current returning to the output pin. If load current falls below this threshold - for example, during light-load or no-load conditions - output voltage may rise uncontrollably. A bleeder resistor from OUT to GND is commonly used to ensure compliance.

Can LM317D2T be used in a negative voltage configuration?

No - the LM317D2T is designed exclusively as a positive adjustable regulator. Its internal architecture references the ADJ pin to the OUT pin, making it unsuitable for direct negative output generation. For negative regulation, use complementary devices such as the LM337D2T, which shares identical D2PAK packaging and pinout but is optimized for −1.2V to −37V operation.

What capacitor values are recommended for input, output, and ADJ pin stability?

A 0.1 µF ceramic capacitor is required between IN and GND, placed within 1 cm of the pin. A 1 µF tantalum (or 25 µF aluminum electrolytic) capacitor is recommended at the output. For improved ripple rejection, connect a 10 µF capacitor between ADJ and GND - this boosts PSRR by ~15 dB at 120 Hz and stabilizes the reference node against noise coupling.

How does thermal performance differ between LM317D2T and LM317T packages?

The LM317D2T in D2PAK has a junction-to-ambient thermal resistance of 62.5°C/W (unmounted), while the LM317T in TO-220 is rated at 50°C/W. However, in PCB-mounted applications with copper pour, the D2PAK's exposed thermal pad enables superior heat transfer - achieving effective R_thj-amb <30°C/W with 4-in² 2-oz copper, outperforming TO-220 in real-world SMT layouts despite its higher nominal rating.

LM317D2T Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Packaging:: Tube

Product Status:: Obsolete

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 FAQ

1.How can I place an order for LM317D2T through Aetrix?

Please submit a Request for Quotation (RFQ) for LM317D2T 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 reliable?

The price and inventory of LM317D2T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317D2T is usually 5 days.

3.What payment methods are accepted for LM317D2T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317D2T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LM317D2T?

LM317D2T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LM317D2T 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?

For technical support, including LM317D2T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317D2T requirements.

6.How does Aetrix verify that LM317D2T is sourced from the original manufacturer or authorized distributors?

All LM317D2T 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 meets industry standards.

7.What is the process for return or replacement of LM317D2T?

All LM317D2T units undergo pre-shipment inspection (PSI). If there is an issue with LM317D2T, 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 part is unused and in its original packaging.

Return procedure for LM317D2T:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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