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Texas Instruments LM108AFKB
- Part No.:
- LM108AFKB
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 14-CDIP (0.300", 7.62mm)
- Datasheet:
-
LM108AFKB.pdf
- Description:
- IC OPAMP GP 1 CIRCUIT 14CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:178
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Product details
Overview
LM1086AFKB from Texas Instruments (formerly National Semiconductor) is a 1.5A low dropout positive voltage regulator in TO-220 package, delivering fixed 3.3V output with 1.5V typical dropout at full load, ±1.5% output voltage accuracy over temperature, and integrated thermal shutdown and current limiting. It serves as a post-regulator for switching supplies and microprocessor core supply in industrial control systems.
For engineers reviewing the LM1086AFKB datasheet, LM1086AFKB pinout, LM1086AFKB application, or LM1086AFKB equivalent, key selection criteria include dropout voltage at 1.5A, load regulation ≤7 mV across 0–1.5A, ripple rejection ≥72 dB at 120 Hz, and compatibility with standard LM317 PCB footprints.
Technical Context
The LM1086AFKB uses a quasi-LDO NPN pass transistor architecture-distinct from PNP LDOs-enabling lower quiescent current while maintaining 1.5V max dropout at 1.5A. Its bandgap reference is zener-trimmed for stability, and internal protection includes foldback current limiting and thermal shutdown triggered at 150°C junction temperature.
It operates with input voltages from 4.75V to 18V and requires ≥10 µF tantalum or ≥50 µF aluminum output capacitance for stability. The fixed 3.3V version integrates precision feedback resistors, eliminating external components required by the adjustable variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 3.300 V ±1.5% (guaranteed over 0–1.5A load and −40°C to +125°C) |
| Maximum Dropout Voltage | 1.5 V at 1.5A load (enables operation with only 4.8V input for 3.3V output) |
| Load Regulation | ≤7 mV (0–1.5A load change at VIN = 5V; ensures stable rail under dynamic CPU loads) |
| Line Regulation | ≤1.0 mV (4.75–18V input range; minimizes output drift during input ripple or sag) |
| Ripple Rejection | ≥72 dB at 120 Hz (with 25 µF tantalum output cap; suppresses switching supply noise) |
| Thermal Shutdown Threshold | 150°C junction temperature (protects against sustained overload or inadequate heatsinking) |
| Quiescent Current | 5–10 mA (low no-load consumption ideal for always-on subsystems) |
Pinout & Package
LM1086AFKB is housed in a 3-lead TO-220 package (NS Drawing T03B), with the tab electrically connected to the output pin and serving as the primary thermal path. Mounting requires insulating hardware if the heatsink is grounded.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Input) | VIN | Unregulated DC input; must be ≥4.75V and ≤18V; requires local 10 µF input capacitor |
| 2 (Output) | VOUT | Regulated 3.3V output; connects to tab for thermal conduction; requires ≥10 µF tantalum output capacitor |
| 3 (Ground) | GND | Reference return for internal circuitry and feedback; must be low-impedance connection to system ground plane |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 3.3V Output | Eliminates external resistor network-reduces BOM count and layout sensitivity vs. adjustable regulators |
| 1.5A Continuous Output Current | Supports high-current digital loads including FPGA I/O banks and ARM Cortex-A series cores |
| Thermal Shutdown + Current Limit | Self-protecting under short-circuit or overtemperature; recovers automatically after fault removal |
| LM317 Pin-Compatible Footprint | Enables drop-in replacement in legacy designs without PCB rework or layout revision |
| Low ESR Capacitor Tolerance | Stable with solid tantalum or aluminum electrolytic caps-avoids costly polymer or ceramic-only solutions |
Applications
| SCSI-2 Active Terminator | Microprocessor Core Supply |
|---|---|
Use Scenario: Termination of differential SCSI-2 bus signals in server backplanes and storage enclosures. IC Role / Device Role / Timing Role: Provides precise 3.3V bias voltage to active termination resistors, ensuring signal integrity at 10 MB/s data rates. Use Value: Tight ±1.5% output tolerance maintains termination impedance within spec, preventing reflections and data corruption. |
Use Scenario: Powering ARM9/ARM11 processor cores requiring clean, stable 3.3V I/O rails. IC Role / Device Role / Timing Role: Low-noise linear post-regulator following a buck converter, reducing switching ripple on sensitive logic interfaces. Use Value: 72 dB ripple rejection suppresses 120 Hz artifacts from upstream converters, preventing timing jitter in synchronous peripherals. |
| Battery Charger Control | Post-Regulation for Switching Supplies |
Use Scenario: Constant-voltage stage in Li-ion battery charging circuits for portable medical devices. IC Role / Device Role / Timing Role: Precision 3.3V reference source for charger IC feedback loop, enabling accurate cell voltage cutoff. Use Value: 0.1% typical load regulation ensures <±5 mV output shift across full charge cycle current range (0–1.5A). |
Use Scenario: Final-stage regulation in telecom power modules where intermediate 5V/12V rails feed point-of-load converters. IC Role / Device Role / Timing Role: Clean, low-dropout buffer that rejects noise from upstream DC/DC stages before powering analog sensors or ADCs. Use Value: 1.5V dropout allows operation from 4.8V inputs-maximizing efficiency when upstream converter output sags under transient load. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar low-dropout linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM1086CT-3.3 | Same silicon, identical electrical specs; differs only in temperature grade (0°C to +125°C vs. −40°C to +125°C for LM1086AFKB) | Not rated for extended industrial or automotive ambient ranges; unsuitable for cold-start environments | Select LM1086AFKB for designs requiring operation below 0°C or full industrial temperature compliance. |
| TLV1117-33CDCY | Lower 800 mA output current; 1.2V dropout at 800 mA; different pinout (SOT-223); no LM317 footprint compatibility | Cannot replace LM1086AFKB without PCB redesign; insufficient for 1.5A microprocessor I/O rails | Consider only for space-constrained, lower-current applications where TO-220 mounting is impractical. |
Compared with LM1086CT-3.3, LM1086AFKB provides guaranteed operation down to −40°C-critical for outdoor industrial controllers-while TLV1117-33CDCY trades current capability and package compatibility for smaller footprint, making it a non-interchangeable alternative rather than a drop-in replacement.
Availability
LM1086AFKB is available at Aetrix Electronics and suitable for industrial control systems, embedded computing platforms, and telecom power management requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.
Supply support for LM1086AFKB 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
Texas Instruments acquired National Semiconductor in 2011 and maintains full technical and manufacturing continuity for legacy analog power products like the LM1086 series.
The LM1086AFKB belongs to TI's industrial-grade linear regulator portfolio, designed specifically for high-reliability post-regulation, noise-sensitive analog subsystems, and legacy-compatible upgrades in cost-optimized power architectures.
FAQ
What is the maximum input voltage rating for LM1086AFKB?
The LM1086AFKB has an absolute maximum input-to-output voltage differential of 27V. Since its output is fixed at 3.3V, the maximum allowable input voltage is 30.3V. However, the recommended operating range is 4.75V to 18V to ensure thermal safety and maintain specified load regulation performance across temperature.
Does LM1086AFKB require an external capacitor on the adjust pin?
No-LM1086AFKB is the fixed 3.3V version and does not have an adjust pin. Only the LM1086-ADJ variants include an adjust terminal requiring optional bypass capacitors for enhanced ripple rejection. The LM1086AFKB integrates internal feedback resistors and operates with just input and output capacitors.
Can LM1086AFKB be used without a heatsink?
LM1086AFKB can operate without an external heatsink only at light loads (<300 mA) and low input-output differentials (<2V) in still-air conditions. At full 1.5A load with 5V input, power dissipation reaches ~2.55W; TO-220 θJA ≈ 50°C/W means junction temperature would exceed 125°C without heatsinking. A minimum 10 cm² copper pour or small clip-on heatsink is strongly recommended.
Is LM1086AFKB pin-compatible with the LM317?
Yes-LM1086AFKB uses the same 3-pin TO-220 pinout (VIN–VOUT–GND) as the LM317, enabling direct PCB footprint replacement. However, unlike the LM317, LM1086AFKB delivers fixed 3.3V output and cannot be adjusted; no external resistors are needed or supported.
What is the minimum load current required for regulation in LM1086AFKB?
The LM1086AFKB does not require a minimum load current to maintain regulation. Unlike some older regulators, its internal circuitry remains stable down to zero load. This eliminates the need for bleed resistors and reduces standby power loss in always-on applications.
LM108AFKB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-CDIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Amplifier Type:
- General Purpose
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- -
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- -
- Current - Input Bias:
- 3 nA
- Voltage - Input Offset:
- -
- Current - Supply:
- -
- Current - Output / Channel:
- -
- Voltage - Supply Span (Min):
- 40 V
- Voltage - Supply Span (Max):
- 40 V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 14-CDIP
LM108AFKB FAQ
1.How can I place an order for LM108AFKB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM108AFKB 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 LM108AFKB reliable?
The price and inventory of LM108AFKB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM108AFKB is usually 5 days.
3.What payment methods are accepted for LM108AFKB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM108AFKB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM108AFKB?
LM108AFKB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM108AFKB 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 LM108AFKB?
For technical support, including LM108AFKB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM108AFKB requirements.
6.How does Aetrix verify that LM108AFKB is sourced from the original manufacturer or authorized distributors?
All LM108AFKB 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 LM108AFKB meets industry standards.
7.What is the process for return or replacement of LM108AFKB?
All LM108AFKB units undergo pre-shipment inspection (PSI). If there is an issue with LM108AFKB, 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 LM108AFKB part is unused and in its original packaging.
Return procedure for LM108AFKB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM108AFKB Tags
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LM358DT
STMicroelectronics
-
LM358DR
Texas Instruments
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LM2904DR
Texas Instruments
-
LM358ADR
Texas Instruments
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LM2904DGKR
Texas Instruments
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LM324DR
Texas Instruments
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MCP6006T-E/OT
Microchip Technology
-
MCP6006UT-E/OT
Microchip Technology
-
LM324PWR
Texas Instruments
-
LM2902PWR
Texas Instruments
-
LM2902DR
Texas Instruments
-
LM358P
Texas Instruments
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