STMicroelectronics L78L15ABUTR

Overview

L78L15ABUTR from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 15 V output at up to 100 mA, with ±4% output voltage tolerance (A-grade), thermal overload protection, and short-circuit current limiting. It requires no external components and is used for local on-card regulation in industrial control modules, sensor signal conditioning circuits, and low-power microcontroller power rails.

For engineers reviewing the L78L15ABUTR datasheet, L78L15ABUTR pinout, L78L15ABUTR application, or L78L15ABUTR equivalent, this page provides verified electrical characteristics, package-specific thermal data, real-world load/line regulation behavior, and validated drop-in alternatives for embedded power design.

Technical Context

The L78L15ABUTR employs internal current limiting and thermal shutdown circuitry, enabling robust operation without external protection components. Its architecture integrates a bandgap reference, error amplifier, and pass transistor in a monolithic silicon structure optimized for stability under varying load and input conditions.

It operates across an input voltage range of 17.5 V to 30 V (for 15 V output), maintains ≤150 mV load regulation over 1–100 mA, and achieves 34–39 dB supply voltage rejection at 120 Hz - critical for noise-sensitive analog subsystems powered from unregulated DC rails.

Key Specifications

Pinout & Package

Supplied in SOT-89 package: compact surface-mount outline with exposed die attach pad for enhanced thermal dissipation. Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM78L15ACZ/NOPB and MC78L15ACP, the L78L15ABUTR offers superior temperature range (−40 to +125 °C), tighter output tolerance (±4%), lower thermal resistance in SOT-89 (55 °C/W with 6 cm² copper), and guaranteed 100 mA delivery - making it optimal for modern high-reliability SMT designs.

Availability

L78L15ABUTR is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body control modules, programmable logic controller I/O cards, and medical patient monitor front-ends requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L78L15ABUTR 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, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space- and reliability-constrained embedded systems where simplicity and proven failure-mode immunity are prioritized.

FAQ

What is the minimum input voltage required for stable 15 V output?

The L78L15ABUTR requires a minimum input voltage of 16.7 V to maintain regulation at full 100 mA load, based on its 1.7 V typical dropout voltage. At lighter loads, input can be reduced further - e.g., 16.2 V sustains 15 V output at 50 mA per load regulation curves in DS0424 Rev 30.

Can L78L15ABUTR be used in parallel to increase output current?

No - the L78L15ABUTR lacks built-in current-sharing capability and has no output current balancing features. Parallel connection risks thermal runaway due to mismatched output voltages and is explicitly discouraged in ST's application guidance. Use a single higher-current regulator or external pass transistor instead.

Is a heat sink required for continuous 100 mA operation?

With the SOT-89 package and 6 cm² copper pour acting as heatsink, the L78L15ABUTR achieves R_thJA = 55 °C/W. At 100 mA and 25 °C ambient, power dissipation is ~170 mW, resulting in ~15 °C junction rise - well within safe limits. No external heatsink is needed under these conditions.

Does L78L15ABUTR support reverse-polarity input protection?

No - the L78L15ABUTR has no internal reverse-voltage protection. Applying negative input relative to ground may cause destructive latch-up or junction breakdown. An external series Schottky diode (e.g., 1N5817) is required if reverse polarity exposure is possible in the system.