STMicroelectronics L78S24CV

Overview

L78S24CV from STMicroelectronics is a three-terminal fixed-output positive linear voltage regulator delivering 24 V at up to 2 A, featuring internal current limiting, thermal shutdown, and safe operating area (SOA) protection. It operates with a minimum input voltage of 27 V (for 1 A load) and supports local on-card regulation in industrial power supplies, motor drive auxiliary rails, and telecom line cards.

For engineers reviewing the L78S24CV datasheet, L78S24CV pinout, L78S24CV application, or L78S24CV equivalent, key selection criteria include dropout voltage behavior at 2 A, thermal resistance (5 °C/W junction-to-case), output noise (170 µV RMS), and short-circuit peak current capability (3 A).

Technical Context

The L78S24CV implements a monolithic series pass transistor architecture with built-in foldback current limiting and thermal foldback. Its SOA protection dynamically restricts power dissipation during overload conditions by reducing output current as junction temperature rises beyond 125 °C.

It requires no external compensation for stability but benefits from an output capacitor (≥10 µF aluminum or ≥1 µF tantalum) to improve transient response. Input voltage must exceed 27 V for full 1 A operation and 33 V for 500 mA under typical test conditions (T_J = 25 °C).

Key Specifications

Pinout & Package

Supplied in TO-220 package (single-gauge variant, 3-lead vertical mount), with metal tab electrically connected to Pin 2 (Ground). Requires mechanical mounting to heatsink via tab for thermal management at >500 mA loads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7824CT and MC7824CD2TR4G, the L78S24CV trades marginal noise and accuracy for superior thermal survivability and integrated SOA protection-critical for unattended industrial deployments where field-replaceability is costly.

Availability

L78S24CV is available at Aetrix Electronics and suitable for industrial PLC power rails, telecom line card bias, motor drive auxiliary supplies, and test equipment power modules requiring stable component supply with long-term lifecycle assurance.

Supply support for L78S24CV 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 broad manufacturing scale and AEC-Q100/IEC 60730 compliance capabilities.

The L78S series belongs to ST's legacy linear regulator product line, designed specifically for ruggedized fixed-voltage local regulation in harsh environments where reliability trumps ultra-low quiescent current or switching efficiency.

FAQ

What is the minimum input voltage required for full 2 A output from the L78S24CV?

The L78S24CV does not guarantee 2 A output across its full operating range. At 2 A, the dropout voltage reaches ~9 V (per Figure 8), requiring ≥33 V input at 25 °C. For reliable 2 A delivery, use ≥35 V input with a heatsink maintaining T_J ≤ 125 °C. Derate linearly above 25 °C ambient.

Can the L78S24CV be used in adjustable configurations?

Yes - the L78S24CV can be configured as an adjustable regulator using external resistors (Figure 20), though its internal reference is fixed at 24 V. To achieve lower voltages, connect a Zener diode between ground and the ADJ pin; for higher outputs, use a resistor divider from output to ADJ. Stability must be verified per application circuit guidelines.

Is an input capacitor mandatory for L78S24CV operation?

An input capacitor is not mandatory for basic regulation but is strongly recommended: a 0.33 µF ceramic capacitor placed within 1 cm of Pins 1 and 2 suppresses high-frequency noise and prevents oscillation during fast line transients. Larger bulk capacitance (≥100 µF) is required if the input source has >1 Ω impedance or is located >10 cm away.

Does the L78S24CV require a heatsink for 1 A continuous operation?

Yes - at 1 A with 33 V input, power dissipation is ~9 W. With R_thJA = 50 °C/W and 25 °C ambient, junction temperature would reach ~275 °C without heatsinking - far exceeding the 150 °C limit. A heatsink with R_thSA ≤ 10 °C/W (combined with thermal compound and proper mounting) is required to maintain T_J ≤ 125 °C.