STMicroelectronics L78M15CV

Overview

L78M15CV from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 15 V at up to 500 mA output current, featuring thermal overload protection, short-circuit protection, and safe operating area (SOA) compensation. It operates with 2 V dropout voltage, ±2 % output voltage tolerance (AB/AC versions), and supports junction temperatures from −40 °C to +125 °C in TO-220FP package - widely deployed in industrial power rails and embedded control subsystems.

For engineers reviewing the L78M15CV datasheet, L78M15CV pinout, L78M15CV application, or L78M15CV equivalent, key selection considerations include guaranteed 15 V regulation under 500 mA load, 54 dB supply voltage rejection at 120 Hz, 90 µV RMS output noise (10 Hz–100 kHz), and thermal shutdown activation at ~150 °C junction temperature.

Technical Context

The L78M15CV integrates a PNP pass transistor with internal current limiting, thermal foldback, and SOA protection circuitry that dynamically reduces output current as input-output differential voltage increases - preventing destructive second breakdown during sustained overload. Its feedback loop is internally compensated for stability with ≥0.33 µF input and ≥0.1 µF output capacitors.

It functions as a local point-of-load regulator without external sense lines, relying on direct connection between ground pin and system reference plane. Output voltage drift is specified at −1 mV/°C over 0–125 °C, and line/load regulation remain within 50 mV and 150 mV respectively under defined test conditions.

Key Specifications

Pinout & Package

Package: TO-220FP (Full Pack), 3-pin vertical mounting variant with insulated tab, rated R_thJC = 5 °C/W and R_thJA = 60 °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 MC78M15BDTG, the L78M15CV delivers superior supply rejection (54 dB vs ≤50 dB), lower output noise (90 µV vs ≥120 µV), and identical ±2 % tolerance with proven thermal robustness in extended temperature operation - making it optimal for precision industrial and medical power rails.

Availability

L78M15CV is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical patient monitor sensors, and test & measurement equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L78M15CV 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 microcontrollers, power management ICs, sensors, and discrete components for industrial, automotive, and consumer markets.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered specifically for robust local regulation in space-constrained, thermally demanding applications where reliability under overload and wide temperature operation are critical.

FAQ

What is the minimum input voltage required for stable 15 V output at 500 mA?

The L78M15CV requires a minimum input voltage of 17 V to maintain regulation at 500 mA due to its 2 V dropout voltage specification. At higher ambient temperatures or with inadequate heatsinking, derating applies - e.g., 18.5 V recommended for continuous 500 mA operation at 85 °C ambient with TO-220FP package.

Does L78M15CV require external capacitors for stability?

Yes - an input bypass capacitor ≥0.33 µF (tantalum or ceramic) is mandatory when the regulator is located >2 cm from the main filter capacitor, and an output capacitor ≥0.1 µF is recommended to improve transient response. No external compensation network is needed; the device is internally compensated for standard capacitor values.

How does thermal shutdown behave during sustained overload?

Under sustained overload, the L78M15CV activates thermal shutdown at ~150 °C junction temperature, halting output current until junction cools to ~130 °C, then resuming regulation. This hysteresis prevents rapid cycling. The TO-220FP package's R_thJA = 60 °C/W means ≥10 cm² copper pour is required for full 500 mA operation at 70 °C ambient.

Can L78M15CV be used in adjustable configurations?

Yes - though designed as a fixed 15 V regulator, it can serve as the core element in adjustable topologies: adding two resistors enables output voltages from 7 V to 30 V (per Figure 20), while series-pass transistor augmentation (Figure 22) supports >500 mA loads with retained short-circuit protection.