STMicroelectronics L78M15ACDT

Overview

L78M15ACDT from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a precise +15 V output at up to 500 mA, featuring ±2 % output voltage tolerance, thermal overload protection, and short-circuit current limiting. It operates across an extended temperature range (0 to 125 °C) and requires only input/output bypass capacitors for stable operation in local on-card power regulation.

For engineers reviewing the L78M15ACDT datasheet, L78M15ACDT pinout, L78M15ACDT application, or L78M15ACDT equivalent, this device serves as a drop-in replacement for legacy 78xx-series regulators in industrial control logic supplies, sensor interface rails, and embedded microcontroller auxiliary power domains where fixed 15 V with high DC accuracy and robust fault protection are required.

Technical Context

The L78M15ACDT implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and safe-area protection-ensuring survivability under sustained overload or junction overheating. Its design eliminates need for external compensation in standard configurations.

It maintains regulation with a minimum 2 V dropout voltage at 25 °C and delivers 15 V ±2 % over load currents from 5 mA to 350 mA and input voltages from 17.5 V to 30 V, while exhibiting 54 dB supply voltage rejection at 120 Hz and 90 µV RMS output noise (10 Hz–100 kHz).

Key Specifications

Pinout & Package

Supplied in DPAK (TO-252) surface-mount package with exposed thermal pad for enhanced heat dissipation; R_thJA = 100 °C/W, R_thJC = 8 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M15CDT/NOPB and MC78M15CDTG, the L78M15ACDT provides tighter output accuracy (±2 % vs. ±4 %), superior supply ripple rejection (54 dB vs. ≤50 dB), and integrated safe-area protection-making it the preferred choice for analog-intensive and thermally constrained designs.

Availability

L78M15ACDT is available at Aetrix Electronics and suitable for industrial PLC I/O modules, medical sensor signal conditioners, and test equipment auxiliary power supplies requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for L78M15ACDT 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The L78Mxx series belongs to ST's precision linear regulator product line, engineered specifically for reliable local DC-DC conversion in space-constrained industrial and medical systems where simplicity, fault resilience, and parametric consistency are prioritized over switching efficiency.

FAQ

What is the minimum input voltage required for the L78M15ACDT to maintain regulation?

The L78M15ACDT requires a minimum input-to-output differential of 2 V at 25 °C to sustain regulation, meaning the lowest valid input voltage is 17 V. At higher junction temperatures or full load, the dropout voltage increases slightly; design margins should include ≥2.2 V headroom for reliable operation across temperature and load extremes.

Can the L78M15ACDT be used in parallel to increase output current?

No-parallel operation is not supported. The L78M15ACDT lacks current-sharing circuitry or matched output impedance; attempting parallel connection risks thermal runaway and uneven current distribution. For >500 mA, use a single higher-current regulator (e.g., L7815CV) or switch-mode solution.

Is an input bypass capacitor mandatory for stable operation?

Yes. A minimum 0.33 µF low-ESR capacitor (tantalum, ceramic, or film) must be placed directly across the input pin and ground, with shortest possible leads. This prevents high-frequency oscillation and ensures stability under fast load transients, especially when input traces exceed 5 cm or connect to noisy bulk supplies.

Does the L78M15ACDT require a heatsink in DPAK package at 500 mA?

At 500 mA with 10 V input-to-output differential (25 V input), power dissipation is ~5 W. With R_thJA = 100 °C/W, junction temperature rise would exceed 500 °C-far beyond rating. A heatsink or copper pour ≥4 cm² is mandatory; for continuous 500 mA, thermal design must achieve ≤100 °C junction rise, typically requiring ≥25 cm² of 2-oz copper or external heatsink.