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onsemi LM317LDG
- Part No.:
- LM317LDG
- Manufacturer:
- onsemi
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM317LDG.pdf
- Description:
- IC REG LIN POS ADJ 100MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,772
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Product details
Overview
LM317LDG from onsemi is a 3-terminal adjustable positive voltage regulator delivering up to 100 mA across an output range of 1.2 V to 37 V, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It operates in floating configuration for high-voltage applications and requires only two external resistors for output programming - widely used for local on-card regulation and precision current regulation.
For engineers reviewing the LM317LDG datasheet, pinout, applications, or equivalent options, key selection considerations include its SOIC-8 package, 1.25 V reference voltage, ±0.7% temperature stability, 60–80 dB ripple rejection, and minimum 3.5 mA load current requirement to maintain regulation.
Technical Context
The LM317LDG implements a floating linear regulator architecture with a precision 1.25 V bandgap reference between output and adjustment terminals. Its feedback loop uses external R1/R2 to set VOUT = 1.25 V × (1 + R2/R1) + IADJR2, where IADJ is tightly controlled below 100 µA.
It integrates protection circuitry including thermal overload shutdown at ~180 °C, foldback current limiting, and safe-area compensation for output transistor reliability. The SOIC-8 variant supports higher power dissipation than TO-92 due to lower junction-to-ambient thermal resistance (180 °C/W vs. 160 °C/W).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 100 mA maximum - sufficient for low-power analog rails, sensor biasing, and microcontroller peripherals. |
| Reference Voltage | 1.25 V typical (1.20–1.30 V) - defines base feedback node accuracy and sets minimum output voltage. |
| Line Regulation | 0.02%/V typical - ensures stable output despite input voltage variation from 3.0 V to 40 V differential. |
| Load Regulation | 0.1 mV typical (≤5 mV max) for VO ≤ 5 V - maintains tight voltage under changing load conditions. |
| Ripple Rejection | 80 dB at 120 Hz - suppresses AC line noise when CADJ = 10 µF is applied to adjustment pin. |
| Thermal Shutdown | Activates at ~180 °C - prevents permanent damage during sustained overload or poor heatsinking. |
| Adjust Pin Current | 50–100 µA - enables high-impedance resistor networks without significant error contribution. |
Pinout & Package
LM317LDG is housed in a Pb-free SOIC-8 (Case 751) surface-mount package measuring 4.9 mm × 3.9 mm × 1.5 mm, optimized for automated assembly and moderate power dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Vin) | Input voltage supply terminal | Accepts unregulated DC input; must be ≥1.25 V above desired VOUT plus dropout margin. |
| 2 (Vout) | Regulated output voltage terminal | Delivers adjustable regulated voltage; connects to R1 top and load; serves as reference return for feedback network. |
| 3 (Vout) | Duplicate output connection | Redundant Vout pin improves current handling and reduces trace resistance impact in PCB layout. |
| 4 (Adjust) | Feedback reference node | Senses 1.25 V below Vout; connected to R1–R2 junction; bypassing with 10 µF improves ripple rejection. |
| 5 (N.C.) | No connect | Internally unused; must remain unconnected per datasheet - no routing or grounding allowed. |
| 6 (Vout) | Duplicate output connection | Third Vout pin enhances thermal and electrical performance by distributing output current across multiple pins. |
| 7 (Vout) | Duplicate output connection | Fourth Vout pin further lowers effective output impedance and improves thermal conduction to PCB copper. |
| 8 (N.C.) | No connect | Internally unused; left floating - no electrical or mechanical tie required. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable output from 1.2 V to 37 V | Enables single BOM part to replace multiple fixed regulators - reduces inventory and simplifies design reuse. |
| Internal thermal shutdown | Self-protects against overheating without external sensing components - eliminates need for discrete thermal cutoff circuits. |
| Floating operation capability | Supports high-side or battery-ground-referenced configurations - enables use in >40 V systems via differential voltage rating. |
| Low adjustment pin current (≤100 µA) | Permits use of high-value resistor dividers (e.g., 240 Ω + 10 kΩ) without loading error - improves output accuracy and efficiency. |
| SOIC-8 package with four Vout pins | Provides lower thermal resistance and higher current capacity than TO-92 - suitable for compact, thermally constrained PCB layouts. |
Applications
| Industrial Sensor Power Supply | Programmable Bench Power Module |
|---|---|
|
Use Scenario: Providing stable, low-noise bias voltage to precision analog sensors (e.g., strain gauges, RTDs) in factory automation systems. IC Role / Device Role / Timing Role: Local linear regulator delivering 3.3 V or 5.0 V from 12 V intermediate rail, rejecting switching noise from upstream DC/DC converters. Use Value: 0.02%/V line regulation and 80 dB ripple rejection ensure sensor signal integrity remains unaffected by input fluctuations or EMI. |
Use Scenario: Core regulation stage in benchtop lab power supplies requiring user-adjustable output voltage and current limiting. IC Role / Device Role / Timing Role: Adjustable voltage source configured with potentiometer and current-sense resistor to implement both voltage and constant-current modes. Use Value: Built-in current limiting and thermal shutdown allow safe operation during short-circuit testing without external protection circuitry. |
| Embedded Microcontroller Core Rail | LED Constant-Current Driver |
|
Use Scenario: Generating clean 3.3 V supply for ARM Cortex-M or PIC microcontrollers in space-constrained IoT edge nodes. IC Role / Device Role / Timing Role: On-board LDO replacement for noisy switchers; provides low-noise, low-quiescent power with minimal external components. Use Value: 1.25 V reference and <100 µA IADJ enable accurate resistor-based setting - achieves ±1% output tolerance over temperature. |
Use Scenario: Driving single or parallel LEDs in signage, instrumentation backlighting, or indicator panels with precise brightness control. IC Role / Device Role / Timing Role: Precision current regulator using fixed resistor between Adjust and Output pins - converts IC into 1.25 V / RSET constant-current source. Use Value: Safe-area compensation and thermal shutdown prevent LED thermal runaway - eliminates need for external current-sense amplifier or FET driver. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable positive voltage regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM317LZG | TO-92 package; 160 °C/W RJA; rated for 0°C to +125°C same as LM317LDG | Better suited for prototyping, through-hole assembly, or low-power applications with natural convection cooling | Select LM317LZG when manual soldering, breadboarding, or thermal load is <250 mW; LM317LDG preferred for SMT volume production and higher power density. |
| NCV317LDG | AEC-Q100 qualified; −40°C to +125°C operating range; automotive PPAP capable | Required for automotive body electronics, infotainment power rails, or industrial systems demanding extended temperature validation | Choose NCV317LDG for automotive-grade designs; LM317LDG is appropriate for commercial/industrial applications within 0°C–125°C ambient. |
Compared with LM317LZG, LM317LDG offers superior thermal performance in SMT layouts and tighter board-level integration; versus NCV317LDG, it lacks AEC-Q100 qualification but delivers identical electrical behavior at lower cost for non-automotive use cases.
Availability
LM317LDG is available at Aetrix Electronics and suitable for industrial sensor power supplies, programmable bench power modules, and embedded microcontroller core rails requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM317LDG 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
onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, and sensor solutions for automotive, industrial, and cloud infrastructure markets.
The LM317 series belongs to onsemi's legacy linear regulator product line, designed specifically for robust, low-cost, adjustable positive voltage regulation in cost-sensitive and thermally constrained applications.
FAQ
What is the maximum input-output voltage differential for LM317LDG?
The LM317LDG supports a maximum input-output voltage differential of 40 Vdc. This rating applies across its full operating temperature range (0°C to +125°C) and enables use in applications such as 48 V telecom systems with 5 V outputs or 24 V industrial rails regulating down to 3.3 V, provided power dissipation remains within thermal limits.
Does LM317LDG require an output capacitor for stability?
No, the LM317LDG is internally compensated and remains stable without an output capacitor. However, adding a 1.0 µF tantalum or 25 µF aluminum electrolytic capacitor at the output improves transient response and suppresses ringing caused by certain PCB trace impedances or load capacitance interactions.
Can LM317LDG be used as a constant-current source?
Yes, the LM317LDG can function as a precision constant-current source by connecting a single resistor between the Adjust and Output pins. With its 1.25 V reference and <100 µA adjustment pin current, output current equals 1.25 V / RSET, enabling accurate LED drivers or sensor excitation circuits without additional active components.
What is the minimum load current required for LM317LDG to maintain regulation?
The LM317LDG requires a minimum load current of 3.5 mA (typical) to 10 mA (max) to maintain output regulation, especially when the input-output differential exceeds 30 V. This is due to internal quiescent current being returned to the output pin; insufficient load causes voltage drift upward beyond the set point.
How does the SOIC-8 package of LM317LDG compare thermally to the TO-92 version?
The LM317LDG in SOIC-8 has a junction-to-ambient thermal resistance of 180 °C/W (at recommended pad size), compared to 160 °C/W for the TO-92 LM317LZG. While the TO-92 offers slightly better natural convection performance, the SOIC-8 provides superior PCB thermal spreading, higher current capability, and compatibility with automated assembly - making it more suitable for dense, production-scale layouts.
LM317LDG Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- 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:
- 100mA
- Current - Quiescent (Iq):
- 10 mA
- Current - Supply (Max):
- -
- PSRR:
- 80dB (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:
- 8-SOIC
LM317LDG FAQ
1.How can I place an order for LM317LDG through Aetrix?
Please submit a Request for Quotation (RFQ) for LM317LDG 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 LM317LDG reliable?
The price and inventory of LM317LDG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317LDG is usually 5 days.
3.What payment methods are accepted for LM317LDG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317LDG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM317LDG?
LM317LDG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM317LDG 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 LM317LDG?
For technical support, including LM317LDG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317LDG requirements.
6.How does Aetrix verify that LM317LDG is sourced from the original manufacturer or authorized distributors?
All LM317LDG 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 LM317LDG meets industry standards.
7.What is the process for return or replacement of LM317LDG?
All LM317LDG units undergo pre-shipment inspection (PSI). If there is an issue with LM317LDG, 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 LM317LDG part is unused and in its original packaging.
Return procedure for LM317LDG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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