STMicroelectronics L78L15ACUTR

Overview

L78L15ACUTR 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, short-circuit protection, and no external components required. It operates across an input voltage range of 17.5–30 V 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 L78L15ACUTR datasheet, L78L15ACUTR pinout, L78L15ACUTR application, or L78L15ACUTR equivalent, this device serves as a drop-in replacement for Zener-diode/resistor regulators-offering lower quiescent current (6.5 mA typ.), improved line/load regulation (250 mV/75 mV max), and higher supply voltage rejection (34–39 dB) in compact TO-92 and SOT-89 packages.

Technical Context

The L78L15ACUTR implements 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 design optimized for stability with minimal external capacitance (0.33 µF input, 0.1 µF output).

It functions as a fixed-output series regulator with a dropout voltage of 1.7 V at 40 mA, supporting operation over junction temperatures from 0 °C to 125 °C. The device maintains output accuracy under varying load (1–100 mA) and input voltage conditions (17.5–30 V), with noise performance specified at 90 µV RMS (10 Hz–100 kHz).

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, vertical mounting), with lead material compliant to RoHS and ECOPACK2 standards. Thermal resistance junction-to-ambient is 200 °C/W (no heatsink), reduced significantly with copper pour on PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L15ACZ and TL750L15CD, the L78L15ACUTR offers superior thermal robustness and tighter tolerance than the former, while providing higher current capability and integrated protection absent in the latter-making it optimal for industrial environments demanding reliability without added circuitry.

Availability

L78L15ACUTR is available at Aetrix Electronics and suitable for industrial sensor interfaces, microcontroller power rails, legacy analog instrumentation, and low-power RS-485 transceiver biasing requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L78L15ACUTR 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 automotive, industrial, and power management ICs with emphasis on reliability and ecological compliance.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in industrial control, instrumentation, and embedded systems where simplicity, protection, and long-term availability are prioritized.

FAQ

What is the maximum allowable input voltage for L78L15ACUTR?

The absolute maximum DC input voltage is 35 V for VO = 12–15 V configurations, per Table 1 of DS0424 Rev 30. Operation above 30 V is not recommended for sustained use, as it exceeds the recommended operating range (17.5–30 V) and increases thermal stress beyond design intent.

Can L78L15ACUTR be used with ceramic output capacitors?

Yes-ST specifies stable operation with ≥0.1 µF ceramic (X7R or better) output capacitors, as confirmed in all test circuits (Figures 3, 13–16). Unlike older 78xx variants, the L78L series does not require ESR-based damping and benefits from low-ESR ceramics for improved transient response.

Does L78L15ACUTR support operation at –40 °C?

No-the 'C' suffix denotes commercial temperature grade (0 to 125 °C junction), not extended industrial grade. For –40 °C operation, the L78L15AB variant (–40 to 125 °C) must be selected; the AC version is not characterized or guaranteed below 0 °C.

How does thermal performance differ between TO-92 and SOT-89 packages?

Per Table 2, TO-92 has R_thJA = 200 °C/W (no heatsink), while SOT-89 achieves 55 °C/W with 6 cm² copper pour. At 100 mA and 30 V input, TO-92 dissipates ~1.5 W and rises ~300 °C above ambient-exceeding safe limits-whereas SOT-89 stays within thermal shutdown threshold with proper PCB layout.