STMicroelectronics L78L24ACD

Overview

L78L24ACD from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 24 V output at up to 100 mA, featuring internal current limiting, thermal overload protection, and short-circuit protection. It requires no external components, operates with a 1.7 V dropout voltage, and maintains ±4% output tolerance over 0–125 °C junction temperature.

For engineers reviewing the L78L24ACD datasheet, L78L24ACD pinout, L78L24ACD application, or L78L24ACD equivalent, this device is selected for local on-card regulation in industrial control modules, low-power sensor interfaces, and legacy analog subsystems where simplicity, reliability, and noise-sensitive DC supply stability are critical.

Technical Context

The L78L24ACD implements a monolithic silicon-based linear regulation architecture with built-in foldback current limiting and thermal shutdown circuitry. Its design eliminates need for external compensation or support capacitors beyond minimum input/output bypassing (0.33 µF / 0.1 µF).

It functions as a fixed-output series pass regulator with a typical quiescent current of 6.5 mA at 25 °C and 6 mA at 125 °C, and delivers 24 V ±4% across load currents from 1 mA to 100 mA and input voltages from 27 V to 38 V.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin plastic transistor-style housing), with standardized pinout: Pin 1 = VOUT, Pin 2 = GND, Pin 3 = VIN. The package supports through-hole mounting and moderate power dissipation when used with minimal PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L24ACZ and MC78L24ACP, the L78L24ACD offers superior noise performance (200 µV vs. ≥250 µV) and tighter line/load regulation, making it optimal for analog-intensive 24 V subsystems where signal integrity outweighs minor quiescent current differences.

Availability

L78L24ACD is available at Aetrix Electronics and suitable for industrial sensor interfaces, legacy PLC I/O modules, low-power analog front-ends, and embedded control subsystems requiring stable component supply with long-lifecycle assurance.

Supply support for L78L24ACD 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, specializing in power management, analog, and microcontroller technologies for industrial, automotive, and consumer markets.

The L78L series was designed specifically for cost-sensitive, space-constrained applications needing simple, robust, fixed-output linear regulation - targeting local on-card power in legacy and new-design industrial electronics.

FAQ

What is the minimum input voltage required for L78L24ACD to maintain regulation?

The L78L24ACD requires a minimum input voltage of 27 V to sustain 24 V output under full 100 mA load, based on its 1.7 V dropout specification. At lighter loads (e.g., 40 mA), regulation holds down to 26.7 V per datasheet Table 21. Input below 27 V risks output collapse, especially at elevated temperature.

Can L78L24ACD be used without input or output capacitors?

No - the datasheet mandates a minimum 0.33 µF input capacitor (ceramic or tantalum) and 0.1 µF output capacitor (ceramic) for stability across all operating conditions. Omitting either risks oscillation, poor transient response, or thermal shutdown during load steps.

Is L78L24ACD compatible with lead-free reflow soldering processes?

Yes - the TO-92 package of L78L24ACD is rated for standard lead-free reflow profiles (JEDEC J-STD-020), with peak temperature up to 260 °C for 30 seconds. The device meets RoHS and REACH compliance requirements as documented in ST's official packaging specifications.

How does thermal performance differ between TO-92 and SO-8 packages for L78L24ACD?

The TO-92 version has R_thJA = 200 °C/W (no heatsink), limiting continuous 100 mA operation to ambient <25 °C unless PCB copper is added. The SO-8 variant (L78L24ACD-TR) achieves R_thJA = 55 °C/W with 6 cm² copper, enabling full-load operation up to 70 °C ambient - a key distinction for thermally constrained layouts.