STMicroelectronics L78M24CDT-TR

Overview

L78M24CDT-TR from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 24 V at up to 0.5 A output current in TO-220FP (IPAK) package. It features thermal overload protection, short-circuit protection, and safe operating area (SOA) compensation. Designed for local on-card regulation in industrial power supplies, motor control logic rails, and embedded system auxiliary supplies, it operates across 0 to 150 °C junction temperature with ±4 % output voltage tolerance (C version).

For engineers reviewing the L78M24CDT-TR datasheet, L78M24CDT-TR pinout, L78M24CDT-TR application, or L78M24CDT-TR equivalent, key selection criteria include dropout voltage (2 V), load regulation (240 mV at 5–200 mA), supply voltage rejection (50 dB at 120 Hz), quiescent current (6 mA), and thermal resistance junction-to-case (5 °C/W).

Technical Context

The L78M24CDT-TR implements a monolithic silicon pass transistor with internal current limiting, thermal shutdown, and SOA protection-enabling robust operation without external protection circuitry. Its architecture relies on a bandgap reference and error amplifier driving the series pass element, with no external feedback required for fixed-output operation.

It supports input voltages up to 40 V DC (for VO = 24 V), delivers stable 24 V output under load currents from 5 mA to 500 mA, and maintains regulation over junction temperatures from 0 to 150 °C. Output noise is 170 µV RMS (10 Hz–100 kHz), and line regulation is specified at 50 mV over VI = 28–38 V at 200 mA load.

Key Specifications

Pinout & Package

Package: TO-220FP (IPAK), 3-pin vertical mounting with insulated tab, RoHS-compliant ECOPACK2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M24CDT and MC78M24CDTG, the L78M24CDT-TR offers superior thermal resilience (150 °C T_J, 5 °C/W R_thJC) and tighter integration into ST's industrial qualification framework-making it optimal for mission-critical, thermally demanding deployments.

Availability

L78M24CDT-TR is available at Aetrix Electronics and suitable for industrial PLC power rails, motor drive auxiliary supplies, medical diagnostic subsystems, and building automation sensor nodes requiring stable component supply across extended temperature and lifecycle requirements.

Supply support for L78M24CDT-TR 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, specializing in automotive, industrial, and power management ICs with strong European manufacturing and qualification infrastructure.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered specifically for ruggedized industrial and automotive auxiliary power applications where thermal resilience, intrinsic protection, and long-term parametric stability are mandatory.

FAQ

What is the minimum input voltage required for L78M24CDT-TR to regulate at full 500 mA load?

The dropout voltage is 2 V at 25 °C, so minimum input is 26 V DC to sustain 24 V output at 500 mA. At elevated junction temperatures, dropout increases slightly-designers should allow ≥27 V margin for worst-case thermal conditions per Figure 8 in DS0425 Rev 24.

Does L78M24CDT-TR require input and output capacitors for stability?

No external capacitors are required for basic stability, but ST recommends a 0.33 µF input bypass (tantalum or ceramic) when the regulator is located >5 cm from the bulk filter, and a 0.1 µF ceramic output capacitor to improve transient response. These values are validated in Figures 17 and 4 of DS0425 Rev 24.

How does the thermal shutdown behavior work during sustained overload?

When junction temperature exceeds ~165 °C, the internal thermal limiter disables the pass transistor until temperature falls by ~15 °C, then automatically resumes regulation. This hiccup-mode recovery prevents latch-up and allows safe operation under intermittent overload-verified in thermal characterization tests on page 16 of DS0425 Rev 24.

Can L78M24CDT-TR be used in adjustable configurations?

Yes-though designed as a fixed 24 V regulator, it can be configured as an adjustable output using external resistors (Figure 19) or constant-current source (Figure 18). Output voltage drift is –1.2 mV/°C, so temperature-compensated designs require additional components like diode-connected transistors per Figure 28 in DS0425 Rev 24.