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onsemi LM317LMX
- Part No.:
- LM317LMX
- Manufacturer:
- onsemi
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM317LMX.pdf
- Description:
- IC REG LIN POS ADJ 100MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,114
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Product details
Overview
LM317LMX from ON Semiconductor is a 3-terminal, adjustable positive-voltage linear regulator delivering ≥100 mA output current with 1.2 V to 37 V programmable output range, internal thermal overload and short-circuit protection, and floating operation capability - used in low-power industrial power supplies and embedded bias rails.
For engineers reviewing the LM317LMX datasheet, pinout, applications, or equivalent options, key selection considerations include its 8-SOIC package, 100 mA continuous output rating, ±0.5% reference voltage tolerance, 0.04% typical line regulation, and compatibility with standard two-resistor feedback networks.
Technical Context
The LM317LMX implements a bandgap-referenced error amplifier driving an NPN pass transistor, with built-in safe-area compensation and current-limit foldback. Its adjustment pin draws only 50–100 μA, enabling high-impedance feedback networks without significant error.
It operates with a minimum input-output differential of 3 V and supports up to 40 V differential, allowing use in floating configurations where the regulator output is elevated above ground - unlike fixed-output regulators requiring ground-referenced input.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 100 mA continuous (at VI−VO ≤ 15 V, PD < PDMAX); enables compact low-power supply designs without heatsinking. |
| Output Voltage Range | 1.2 V to 37 V (adjustable via two external resistors); supports wide-range biasing for analog circuits and microcontrollers. |
| Reference Voltage (VREF) | 1.25 V nominal (1.20–1.30 V over temp); sets precision of output programming and stability under load variation. |
| Line Regulation | 0.04% / V typical (3–40 V VI−VO range); ensures stable output despite input rail fluctuations in unregulated DC sources. |
| Load Regulation | 25 mV max (VO ≤ 5 V, 10–100 mA); maintains tight voltage control across varying load conditions in sensor or logic rails. |
| Ripple Rejection | 66 dB min (120 Hz, with 10 μF ADJ-bypass capacitor); suppresses rectified AC ripple in linear post-regulation stages. |
| Adjust Pin Current | 50–100 μA; allows use of high-value resistor dividers (e.g., 240 Ω + 1.8 kΩ) without loading error. |
Pinout & Package
LM317LMX is housed in an 8-pin SOIC (JEDEC MS-012, 0.150-inch narrow body) package. Pins 1, 2, 3, 6, and 7 are internally connected to the output terminal; Pin 4 is the adjustment terminal; Pins 5 and 8 are no-connect (NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 6, 7 | Output | Common output node; multiple pins reduce trace resistance and improve thermal conduction to PCB copper. |
| 4 | Adjust | Feedback reference point; connects to resistor divider midpoint to set output voltage via VOUT = 1.25 V × (1 + R2/R1). |
| 5, 8 | No Connect | Not bonded internally; must remain unconnected on PCB to avoid parasitic coupling or latch-up risk. |
Key Features
| Feature | Design Value |
|---|---|
| Internal thermal shutdown | Automatically disables output when junction temperature exceeds safe limit (~160°C), preventing permanent damage during overload or poor heatsinking. |
| Short-circuit current limiting | Clamps output current to ~150 mA during output-to-ground fault, enabling safe recovery without external fusing. |
| Floating operation support | Allows regulator to operate with output referenced above ground (e.g., in high-side current sources or negative-rail generators), expanding topology flexibility. |
| Safe-area compensated pass transistor | Prevents second breakdown in the internal NPN pass device under simultaneous high voltage and current stress, improving reliability in transient conditions. |
| Low adjustment pin current drift | ΔIADJ ≤ 5 μA over full VI−VO and load range, minimizing output voltage error caused by resistor-divider current mismatch. |
Applications
| Industrial Sensor Bias Supply | Embedded Microcontroller Core Rail |
|---|---|
|
Use Scenario: Powering analog front-end sensors (e.g., pressure transducers, RTDs) in factory automation modules where clean, stable 3.3 V or 5 V is required from a noisy 12 V DC bus. IC Role / Device Role / Timing Role: Adjustable linear regulator providing low-noise, ripple-free bias voltage; functions as primary post-regulator after bulk DC/DC conversion. Use Value: Delivers 0.003% RMS output noise and 66 dB ripple rejection - critical for sub-12-bit ADC accuracy and offset stability over temperature. |
Use Scenario: Generating 1.8 V or 3.3 V core voltage for ARM Cortex-M0+ MCUs in battery-powered edge nodes with limited PCB area and no active cooling. IC Role / Device Role / Timing Role: Low-current adjustable LDO replacement; regulates from intermediate 5 V rail with minimal external components. Use Value: 100 mA output capacity and SOIC package allow direct integration into space-constrained layouts while maintaining ±2% output accuracy over 0–125°C. |
| Programmable Current Source | Lab Bench Power Module |
|
Use Scenario: Building a digitally controlled constant-current source for LED characterization or photodiode biasing using a DAC-driven voltage at the ADJ pin. IC Role / Device Role / Timing Role: Precision current regulator configured in floating mode; output current determined by IOUT ≈ 1.25 V / RSET. Use Value: 50–100 μA ADJ pin current and <0.5% VREF tolerance enable ±1% current setting accuracy without calibration. |
Use Scenario: Modular benchtop power supply channel with user-adjustable 1.2–30 V output and current limit indication, built into educational or service lab equipment. IC Role / Device Role / Timing Role: Main adjustable regulator IC in discrete linear supply architecture; paired with potentiometer, metering, and series pass transistor. Use Value: 40 V max input-output differential and thermal protection allow safe operation across full voltage range without manual derating or thermal monitoring. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM317LDR2G | TO-220-3 package, 1.5 A output rating, higher thermal mass; same electrical specs but different pinout (Input–Output–Adj). | Used where higher current (>100 mA) or through-hole mounting is required; not drop-in compatible due to package and pinout mismatch. | Select LM317LDR2G only when >100 mA output or TO-220 mechanical fit is mandatory; requires PCB redesign. |
| TLV1117-33CDR | Fixed 3.3 V output, SOT-223 package, 800 mA rating, lower dropout (1.2 V), no ADJ pin; lacks adjustability and floating capability. | Suitable for cost-sensitive, fixed-voltage applications with tight space constraints; cannot replace LM317LMX in variable-output or floating topologies. | Choose TLV1117-33CDR only for fixed 3.3 V use cases where adjustability and floating operation are unnecessary. |
Compared with LM317LDR2G and TLV1117-33CDR, the LM317LMX uniquely balances SOIC footprint, 100 mA capability, full 1.2–37 V adjustability, and floating operation - making it optimal for compact, programmable, low-to-moderate power linear regulation where layout flexibility and topology choice matter.
Availability
LM317LMX is available at Aetrix Electronics and suitable for industrial sensor bias supplies, embedded microcontroller core rails, and programmable current sources requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LM317LMX 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
ON Semiconductor (formerly Fairchild Semiconductor) is a global semiconductor manufacturer specializing in power management, analog, and logic solutions for automotive, industrial, and cloud infrastructure markets.
The LM317LMX belongs to ON Semiconductor's legacy linear regulator product line, designed for robust, low-cost, and easy-to-use adjustable voltage regulation in non-critical power applications where simplicity and reliability outweigh ultra-low dropout or switching efficiency.
FAQ
What is the maximum input-output voltage differential supported by the LM317LMX?
The LM317LMX supports a maximum input-output voltage differential of 40 V, as specified in its Absolute Maximum Ratings. This allows the LM317LMX to operate safely in floating configurations or with high-input rails up to 37 V + 40 V = 77 V referenced to ground - provided power dissipation remains within limits and thermal design accommodates the resulting heat.
Can the LM317LMX be used in a floating configuration to generate a negative output voltage?
No - the LM317LMX is a positive adjustable regulator and cannot produce negative output voltages. However, it can be used in a floating configuration (e.g., with its input and output referenced above ground) to create a positive voltage relative to a non-ground reference, such as in high-side current sources or isolated bias supplies. For true negative regulation, a complementary device like LM337LMX is required.
What is the purpose of the NC pins (5 and 8) on the LM317LMX 8-SOIC package?
Pins 5 and 8 on the LM317LMX are no-connect (NC) terminals - they are not bonded to any internal circuitry and serve no electrical function. These pins must remain unconnected on the PCB layout to prevent unintended coupling, noise injection, or potential latch-up. Their presence is purely for mechanical symmetry and package standardization, not functional routing.
How does the LM317LMX handle thermal overload, and what happens when it triggers?
The LM317LMX incorporates internal thermal shutdown that activates when the junction temperature exceeds approximately 160°C. When triggered, the LM317LMX disables its output pass transistor, dropping output voltage to near zero until die temperature falls below the hysteresis threshold (~140°C). This protects the LM317LMX from permanent damage during sustained overload or inadequate heatsinking, and recovery is automatic upon cooling.
Is the LM317LMX pin-compatible with the LM317LZ in TO-92 packaging?
No - the LM317LMX (8-SOIC) and LM317LZ (TO-92) have fundamentally different pinouts and package footprints. The TO-92 version uses a 3-pin arrangement (Adj–Output–Input), while the LM317LMX uses an 8-pin SOIC with Output on pins 1/2/3/6/7, Adj on pin 4, and NC on pins 5/8. They are functionally equivalent but not mechanically or electrically interchangeable without PCB redesign.
LM317LMX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
LM317LMX FAQ
1.How can I place an order for LM317LMX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM317LMX 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 LM317LMX reliable?
The price and inventory of LM317LMX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM317LMX is usually 5 days.
3.What payment methods are accepted for LM317LMX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM317LMX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM317LMX?
LM317LMX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM317LMX 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 LM317LMX?
For technical support, including LM317LMX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM317LMX requirements.
6.How does Aetrix verify that LM317LMX is sourced from the original manufacturer or authorized distributors?
All LM317LMX 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 LM317LMX meets industry standards.
7.What is the process for return or replacement of LM317LMX?
All LM317LMX units undergo pre-shipment inspection (PSI). If there is an issue with LM317LMX, 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 LM317LMX part is unused and in its original packaging.
Return procedure for LM317LMX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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