STMicroelectronics L78L24ACZ-AP

Overview

L78L24ACZ-AP 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 for basic operation and is specified for 0–125 °C junction temperature with ±4% output voltage tolerance (A grade). It serves as a robust local regulation solution in industrial control power rails.

For engineers reviewing the L78L24ACZ-AP datasheet, L78L24ACZ-AP pinout, L78L24ACZ-AP application, or L78L24ACZ-AP equivalent, this device is evaluated for low-noise, thermally stable 24 V supply generation in space-constrained embedded systems where dropout voltage (1.7 V), quiescent current (6.5 mA at 25 °C), and supply voltage rejection (31–37 dB at 120 Hz) are critical selection criteria.

Technical Context

The L78L24ACZ-AP employs monolithic bipolar technology with built-in foldback current limiting and thermal shutdown circuitry, enabling self-protection under sustained overload or ambient temperature extremes. Its architecture eliminates need for external compensation or bypass capacitors beyond minimum input/output decoupling (0.33 µF / 0.1 µF).

It operates across an input voltage range of 27–38 V for regulated 24 V output, with line regulation of ≤300 mV and load regulation of ≤100 mV over 1–40 mA output current at 25 °C. Output noise is 200 µV RMS (10 Hz–100 kHz), and dropout voltage remains stable at 1.7 V independent of load within specification.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, straight lead configuration), with leads identified as Input (Pin 1), Ground (Pin 2), and Output (Pin 3) per Figure 2 of DS0424 Rev 30. The package uses epoxy molding compound and is 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 LM78L24ACZ/NOPB and MC78L24ACP, the L78L24ACZ-AP offers superior output accuracy (±4% vs ±5%), lower noise (200 µV vs ≥300 µV), and guaranteed 100 mA operation across 0–125 °C - making it optimal for industrial and automotive environments demanding long-term stability.

Availability

L78L24ACZ-AP is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical instrumentation requiring stable component supply, long lifecycle support, and consistent parametric performance across production batches.

Supply support for L78L24ACZ-AP 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 silicon solutions for automotive, industrial, and power management applications.

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

FAQ

What is the minimum input voltage required for regulation at full 100 mA load?

The L78L24ACZ-AP requires a minimum input voltage of 25.7 V to maintain 24 V output at 100 mA, calculated from its 1.7 V dropout voltage specification. Below this, output voltage drops linearly with input; operation below 27 V input is not recommended for guaranteed regulation across temperature.

Can this regulator be used with an input voltage higher than 38 V?

No - the absolute maximum input voltage is 40 V for VO = 18–24 V devices (per Table 1), but continuous operation above 38 V violates the recommended operating condition and risks thermal runaway or premature failure due to excessive power dissipation in the TO-92 package.

Is a heat sink required for 100 mA operation at 25 °C ambient?

At 25 °C ambient and 100 mA output, power dissipation is (33 V − 24 V) × 0.1 A = 0.9 W. With TO-92 R_thJA = 200 °C/W, junction temperature rise would be ~180 °C - exceeding the 125 °C limit. A minimum copper pour (≥6 cm²) is mandatory; discrete heat sinking is strongly advised for sustained 100 mA use.

Does the L78L24ACZ-AP require input/output capacitors, and what values are validated?

Yes - ST specifies 0.33 µF ceramic at the input and 0.1 µF ceramic at the output, placed as close as possible to the respective pins. These values ensure stability across all operating conditions; larger values improve ripple rejection but do not affect regulation integrity per datasheet test circuits.