STMicroelectronics L78M24CDT

Overview

L78M24CDT from STMicroelectronics is a fixed-output, three-terminal positive linear voltage regulator delivering 24 V at up to 500 mA, featuring ±2 % output voltage tolerance, thermal overload protection, short-circuit current limiting, and safe operating area (SOA) protection. It operates across an extended temperature range (0 °C to +125 °C) and requires only two external bypass capacitors for stable operation in industrial power supply rails.

For engineers reviewing the L78M24CDT datasheet, L78M24CDT pinout, L78M24CDT application, or L78M24CDT equivalent, key selection criteria include dropout voltage (2 V), load regulation (240 mV max at 5–200 mA), supply voltage rejection (50 dB at 120 Hz), output noise (170 µV RMS), and DPAK package thermal resistance (R_thJA = 100 °C/W).

Technical Context

The L78M24CDT implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and SOA compensation-ensuring robustness under sustained overload or short-circuit conditions. Its fixed 24 V output eliminates need for external feedback networks, simplifying local point-of-load regulation.

Designed for use with input voltages from 27 V to 38 V, it maintains regulation over full load (5–350 mA) and junction temperature (0–125 °C), with line regulation of ≤30 mV and load regulation of ≤240 mV under specified test conditions. Output voltage drift is –1.2 mV/°C at 5 mA load.

Key Specifications

Pinout & Package

The L78M24CDT is housed in a surface-mount DPAK (TO-252) package with exposed thermal pad, optimized for PCB heat dissipation without additional heatsink in moderate-power applications.

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 provides tighter output tolerance (±2 %), superior thermal robustness (R_thJA = 100 °C/W), and integrated SOA protection - making it the preferred choice for industrial systems requiring long-term reliability under variable load and ambient conditions.

Availability

L78M24CDT is available at Aetrix Electronics and suitable for industrial automation, motor control, and building management systems requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for L78M24CDT 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 quality certification.

The L78Mxx series belongs to ST's legacy linear regulator product line, designed specifically for ruggedized industrial point-of-load regulation where simplicity, reliability, and thermal resilience are prioritized over efficiency.

FAQ

What is the minimum input voltage required for the L78M24CDT to maintain regulation?

The L78M24CDT requires a minimum input-to-output differential voltage of 2 V (dropout voltage) to sustain regulation. With a nominal 24 V output, this means VI must be ≥26 V under typical conditions. The datasheet specifies guaranteed operation from 27 V to 38 V, accounting for line and load variation.

Can the L78M24CDT be used in parallel to increase output current?

No - the L78M24CDT lacks built-in current-sharing capability and has no output offset trimming. Parallel connection risks thermal imbalance and current hogging due to inherent output voltage tolerances (±2 %). For >500 mA, use a single higher-current regulator or switch-mode solution.

Is a heatsink required for continuous 500 mA operation?

At 500 mA with 27 V input (3 V dropout), power dissipation is ~1.5 W. With R_thJA = 100 °C/W and 25 °C ambient, junction temperature rises ~175 °C - exceeding the 125 °C limit. A minimal copper pour (≥4 cm²) or small heatsink is mandatory for full-load operation.

Does the L78M24CDT support adjustable output voltage configurations?

Yes - though designed as a fixed 24 V regulator, it can be configured as an adjustable regulator using external resistors per Figure 18 in the datasheet. Output range is 7.0 V to 20 V, but VI–VO must remain ≥2.0 V; it cannot generate 24 V in adjustable mode.