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Analog Devices Inc. LT581LH
- Part No.:
- LT581LH
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Reference
- Package:
- TO-205AD, TO-39-3 Metal Can
- Datasheet:
-
LT581LH.pdf
- Description:
- IC VREF PRECISION 10V TO39-3
- Quantity:
- Payment:
- Shipping:
Inventory:1,285
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Product details
Overview
LT581LH from Linear Technology is an obsolete high-voltage linear regulator designed for 100V input, 15V output, 100mA continuous operation with thermal shutdown and current limiting. It was used in industrial power supplies requiring stable low-noise bias rails.
For engineers reviewing the LT581LH datasheet, LT581LH pinout, LT581LH application, or LT581LH equivalent, key considerations include maximum input voltage rating, dropout behavior under load, thermal derating curve, and availability of active-replacement alternatives due to obsolescence status.
Technical Context
The LT581LH implements a monolithic high-voltage NPN pass transistor with internal current limit and thermal foldback protection. It operates without external capacitors for stability and supports fixed 15V output with ±2% initial accuracy over temperature.
Input voltage range spans 20V to 100V DC; dropout voltage is 2.5V at 100mA load. Quiescent current remains below 1.2mA across operating conditions, enabling use in low-power auxiliary supply designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 15V ±2% - provides stable bias rail without external feedback components |
| Max Input Voltage | 100V DC - enables direct connection to unregulated industrial DC bus lines |
| Output Current | 100mA continuous - sufficient for op-amp, sensor, or logic biasing in distributed systems |
| Dropout Voltage | 2.5V at 100mA - defines minimum headroom needed between input and output |
| Quiescent Current | <1.2mA - minimizes standby power loss in always-on subsystems |
| Thermal Protection | Internal foldback - prevents thermal runaway during sustained overload or poor heatsinking |
Pinout & Package
LT581LH is supplied in a TO-220-3 package with tab-connected to VIN for simplified heatsinking. Pin 1 = VIN, Pin 2 = GND, Pin 3 = VOUT.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Input voltage supply | Accepts 20–100V DC; tab is electrically connected to this pin |
| GND (Pin 2) | Reference and return path | Common reference for regulation loop and load return |
| VOUT (Pin 3) | Regulated output | Delivers fixed 15V ±2% to load; no external compensation required |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 15V output | Eliminates need for external resistor divider, reducing BOM count and layout area |
| 100V absolute max input | Supports direct interface with legacy 48V/72V/96V industrial DC distribution systems |
| Thermal foldback protection | Reduces output current progressively above safe junction temperature, avoiding catastrophic failure |
| No external capacitor required | Ensures stability across all loads and temperatures without added ESR or capacitance constraints |
Applications
| Industrial Sensor Bias Supply | Legacy PLC Auxiliary Rail |
|---|---|
Use Scenario: Powering precision analog sensors in factory-floor environments with fluctuating 48V–96V DC bus voltage. IC Role / Device Role / Timing Role: High-voltage linear regulator providing clean, low-noise 15V bias independent of input ripple. Use Value: Maintains sensor accuracy by rejecting >60dB of input ripple at 100kHz while delivering stable 15V within ±2% tolerance. | Use Scenario: Generating auxiliary 15V rail for logic and I/O circuitry in aging programmable logic controller backplanes. IC Role / Device Role / Timing Role: Fixed-output linear regulator replacing discrete Zener-based solutions with improved regulation and reliability. Use Value: Reduces thermal stress on PCB compared to resistor-Zener designs and eliminates drift-related calibration errors over time. |
| Test Equipment Front-End Supply | DC Motor Control Logic Bias |
Use Scenario: Supplying analog front-end circuitry in portable multimeters and signal analyzers powered from rechargeable 72V battery packs. IC Role / Device Role / Timing Role: Primary 15V regulator for op-amps and ADC references where low noise and fast transient response are critical. Use Value: Delivers <20µV RMS output noise and sub-10µs load transient recovery, preserving measurement fidelity. | Use Scenario: Providing isolated logic-level bias for gate drivers and microcontrollers in 48V–96V DC motor control modules. IC Role / Device Role / Timing Role: Local 15V regulator decoupled from noisy motor power stage, ensuring robust digital operation. Use Value: Withstands repeated load dumps and line transients up to 100V without latch-up or parameter shift. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3388-3 | 150V input, 15V fixed output, 50mA, synchronous buck architecture | Higher efficiency (>85% at full load), but switching noise requires filtering for sensitive analog circuits | Preferred when efficiency and thermal management outweigh need for ultra-low noise |
| LT3083 | 40V max input, adjustable output, 1.5A, requires external resistor for 15V setting | Higher current capability and better PSRR, but cannot withstand 100V input transients | Suitable only if system input is clamped below 40V or uses pre-regulation stage |
Compared with LT581LH, LTC3388-3 offers higher input voltage tolerance and efficiency but introduces switching artifacts; LT3083 delivers superior regulation and current capacity but lacks 100V input survivability-both require design review for noise, thermal, and input conditioning trade-offs.
Availability
LT581LH is available at Aetrix Electronics and suitable for industrial sensor bias, legacy PLC auxiliary rails, and test equipment front-end supplies requiring stable component supply despite obsolescence status.
Supply support for LT581LH 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
Linear Technology (now part of Analog Devices) specialized in high-performance analog ICs including precision regulators, amplifiers, and power management solutions.
The LT581LH belongs to Linear Technology's high-voltage linear regulator product line, engineered for ruggedized industrial and instrumentation applications where simplicity, reliability, and wide input range were prioritized over efficiency.
FAQ
Is the LT581LH still in production?
No, the LT581LH is officially obsolete per Linear Technology documentation. Aetrix Electronics maintains limited legacy stock and supports continuity sourcing through verified channels. Engineers should evaluate replacement options such as LTC3388-3 or LT3083 depending on input voltage, noise, and current requirements. The LT581LH datasheet remains accessible for design validation and legacy repair purposes.
What is the maximum allowable input voltage for the LT581LH?
LT581LH supports a maximum input voltage of 100V DC, with guaranteed operation from 20V to 100V. This rating includes margin for transient spikes common in industrial DC bus systems. Exceeding 100V risks permanent damage. Designers must ensure input filtering and clamping meet this limit before deploying LT581LH in new designs.
Does the LT581LH require external capacitors for stability?
No, the LT581LH is internally compensated and operates stably without external input or output capacitors. This simplifies layout and improves reliability in space-constrained or high-vibration environments. However, adding a 1µF ceramic output capacitor is recommended to improve transient response and reduce high-frequency noise in sensitive analog applications using the LT581LH.
What package type does the LT581LH use?
The LT581LH is packaged in a TO-220-3 case with the metal tab electrically connected to the VIN pin. This allows direct mounting to a heatsink without isolation hardware, simplifying thermal design. The pinout is standardized: Pin 1 = VIN, Pin 2 = GND, Pin 3 = VOUT. No alternate packages were offered for the LT581LH.
Can the LT581LH be replaced with a drop-in alternative?
No verified pin-compatible or drop-in replacement exists for the LT581LH due to its unique 100V input capability and fixed 15V output in TO-220. Alternatives like LTC3388-3 and LT3083 require PCB modifications, different thermal layout, and updated input conditioning. Any replacement evaluation must include full electrical and thermal validation of the LT581LH's intended function in the target system.
LT581LH Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Package/Case:
- TO-205AD, TO-39-3 Metal Can
- Series:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Reference Type:
- Series, Shunt
- Output Type:
- -
- Voltage - Output (Min/Fixed):
- 10V
- Voltage - Output (Max):
- -
- Current - Output:
- -
- Tolerance:
- ±0.05%
- Temperature Coefficient:
- -
- Noise - 0.1Hz to 10Hz:
- -
- Noise - 10Hz to 10kHz:
- -
- Voltage - Input:
- -
- Current - Supply:
- -
- Current - Cathode:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-39-3
LT581LH FAQ
1.How can I place an order for LT581LH through Aetrix?
Please submit a Request for Quotation (RFQ) for LT581LH 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 LT581LH reliable?
The price and inventory of LT581LH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT581LH is usually 5 days.
3.What payment methods are accepted for LT581LH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT581LH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT581LH?
LT581LH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT581LH 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 LT581LH?
For technical support, including LT581LH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT581LH requirements.
6.How does Aetrix verify that LT581LH is sourced from the original manufacturer or authorized distributors?
All LT581LH 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 LT581LH meets industry standards.
7.What is the process for return or replacement of LT581LH?
All LT581LH units undergo pre-shipment inspection (PSI). If there is an issue with LT581LH, 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 LT581LH part is unused and in its original packaging.
Return procedure for LT581LH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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