onsemi MC78L18ACPRA

Overview

MC78L18ACPRA from onsemi is a 100 mA, fixed +18 V positive linear voltage regulator in TO-92 package with internal short-circuit current limiting, thermal shutdown, and no external components required. It delivers stable output under 1.0–100 mA load across 0°C to +125°C junction temperature, used in low-power industrial control, sensor signal conditioning, and embedded microcontroller power rails.

For engineers reviewing the MC78L18ACPRA datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (1.7 V typ), line regulation (≤325 mV), load regulation (≤170 mV), thermal resistance (200°C/W), and Pb-free TO-92 packaging for cost-sensitive, space-constrained designs.

Technical Context

The MC78L18ACPRA implements a monolithic series-pass transistor regulator architecture with built-in thermal overload protection and foldback current limiting. Its internal reference and error amplifier maintain output regulation without external feedback components.

Designed for fixed-output operation, it requires only input and output bypass capacitors (0.33 µF and 0.1 µF) for stability and transient response-no compensation network needed. Input voltage must exceed 21.4 V to ensure regulation at full load and ambient extremes.

Key Specifications

Pinout & Package

MC78L18ACPRA uses the industry-standard TO-92 plastic package (Case 029), with leads bent for tape-and-reel handling. Thermal performance relies on PCB copper area; no heatsink pad or exposed tab.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78L18ACPG and LM78L18ACZ, the MC78L18ACPRA offers optimized tape-and-reel delivery for automated SMT lines, lowest quiescent current in its family, and tighter line regulation-making it preferred for high-reliability, volume-manufactured industrial controls.

Availability

MC78L18ACPRA is available at Aetrix Electronics and suitable for industrial sensor power supplies, microcontroller core rails, and low-power analog front-ends requiring stable component supply, RoHS compliance, and TO-92 through-hole compatibility.

Supply support for MC78L18ACPRA 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MC78L00A Series-including MC78L18ACPRA-is designed for cost-sensitive, low-current fixed-voltage regulation in space-constrained industrial and consumer electronics where simplicity, reliability, and thermal robustness are essential.

FAQ

What is the maximum input voltage rating for MC78L18ACPRA?

The MC78L18ACPRA has an absolute maximum input voltage of 40 Vdc for 24 V output variants. However, for reliable operation at full load and temperature, the recommended maximum continuous input is 33 Vdc per the electrical characteristics table-exceeding this risks thermal overload or reduced lifetime.

Does MC78L18ACPRA require external capacitors to operate?

Yes, MC78L18ACPRA requires a 0.33 µF input bypass capacitor (placed close to pins 3 and 2) and recommends a 0.1 µF output capacitor (across pins 1 and 2). These stabilize operation under dynamic loads and suppress high-frequency noise-omitting them may cause oscillation or poor transient response.

Can MC78L18ACPRA be used in automotive applications?

No-MC78L18ACPRA is rated for 0°C to +125°C junction temperature and lacks AEC-Q100 qualification. For automotive use, select the NCV78L18ABPG variant (−40°C to +125°C, PPAP-capable, AEC-Q100 qualified), which shares identical regulation specs but meets automotive reliability standards.

What is the thermal resistance (R_JA) of MC78L18ACPRA in its TO-92 package?

The MC78L18ACPRA has a thermal resistance of 200°C/W (Junction-to-Ambient) in the TO-92 package (Case 029) with no heatsink. This value assumes standard PCB mounting; adding copper pour reduces R_JA, but the datasheet does not specify a θ_JC due to plastic package limitations.

How does MC78L18ACPRA handle short-circuit conditions?

MC78L18ACPRA features internal foldback current limiting that reduces output current during a short, combined with thermal shutdown that disables the output if junction temperature exceeds ~150°C. Both protections are fully integrated-no external components are needed to survive sustained shorts.