STMicroelectronics L78L24CD

Overview

L78L24CD 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 and is specified for ±4% output voltage tolerance (C-grade), with 1.7 V dropout voltage and 200 µV RMS output noise (10 Hz–100 kHz). It serves as a robust local regulation solution in industrial control modules and sensor signal conditioning circuits.

For engineers reviewing the L78L24CD datasheet, L78L24CD pinout, L78L24CD application, or L78L24CD equivalent, this page provides verified electrical characteristics, TO-92 package details, thermal resistance data, load/line regulation behavior, and validated alternative parts for fixed-voltage low-current power rail design.

Technical Context

The L78L24CD implements a monolithic silicon voltage regulator architecture with built-in foldback current limiting and thermal shutdown circuitry, enabling fault resilience without external protection components. Its output voltage is trimmed during manufacturing to maintain ±4% accuracy over temperature (0–125 °C junction) and load (1–100 mA).

It operates with a minimum input-to-output differential of 1.7 V and delivers stable regulation across input voltages from 27 V to 38 V. Supply voltage rejection is 31–37 dB at 120 Hz under 40 mA load, and quiescent current remains tightly controlled at 6.5 mA (25 °C) and 6 mA (125 °C).

Key Specifications

Pinout & Package

Supplied in the TO-92 through-hole package (JEDEC TO-92 variant), the L78L24CD uses a standard three-pin configuration with exposed emitter tab for thermal conduction. The package supports PCB copper pour heat-sinking to extend safe operating area under continuous 100 mA load.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L24ACZ and MC78L24CP, the L78L24CD offers superior output accuracy (±4%), lower noise (200 µV), and guaranteed 100 mA delivery - making it the preferred choice for industrial analog signal chains requiring stable, low-drift biasing.

Availability

L78L24CD is available at Aetrix Electronics and suitable for industrial sensor interfaces, PLC I/O modules, embedded controller peripherals, and legacy equipment retrofits requiring stable component supply and long-lifecycle support.

Supply support for L78L24CD 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local voltage regulation in space-constrained and thermally demanding embedded systems.

FAQ

What is the minimum input voltage required for the L78L24CD to regulate properly?

The L78L24CD requires a minimum input-to-output differential of 1.7 V. For its nominal 24 V output, the absolute minimum input voltage is 25.7 V. However, ST specifies guaranteed regulation starting at 27 V input to accommodate line regulation drift and transient margins across temperature and load.

Can the L78L24CD be used in parallel to increase output current?

No - the L78L24CD lacks current-sharing capability and is not designed for parallel operation. Attempting to parallel units risks thermal runaway due to mismatched dropout voltages and load distribution. For higher current, use an external pass transistor or select a higher-current regulator such as the L7824CV.

Is a bypass capacitor required on the input pin?

Yes - ST recommends a 0.33 µF ceramic capacitor between VIN and GND, placed as close as possible to the device. This suppresses high-frequency noise and prevents oscillation caused by source inductance, especially when powered from long traces or switch-mode supplies.

Does the L78L24CD support operation at –40 °C ambient temperature?

No - the L78L24CD (suffix 'C') is rated for 0 °C to 125 °C junction temperature. For –40 °C operation, the AB-grade variant (e.g., L78L24ABD) must be selected, which guarantees functionality from –40 °C to 125 °C and is offered in the same TO-92 package.