onsemi MC78L18ABP

Overview

MC78L18ABP 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 dropout voltage of 1.7 V at 25°C. It operates across −40°C to +125°C junction temperature and requires no external components for basic regulation in low-power industrial control, sensor interfaces, and legacy analog subsystems.

For engineers reviewing the MC78L18ABP datasheet, pinout, applications, or equivalent options, key selection criteria include input voltage range (21.4–33 V), load regulation (≤170 mV over 1–100 mA), ripple rejection (33–48 dB at 120 Hz), and thermal resistance (200°C/W in TO-92) - all critical for stable 18 V biasing in space-constrained embedded designs.

Technical Context

The MC78L18ABP uses a monolithic silicon design with built-in protection circuitry: thermal overload protection shuts down the device above ~150°C junction temperature, and internal current limiting caps output at ~150 mA typical. Its architecture relies on a PNP pass transistor with feedback-controlled reference and error amplifier, delivering fixed output without external resistors.

It functions as a three-terminal series regulator where input voltage must exceed output by ≥1.7 V (dropout) under full load; line regulation is specified at ≤325 mV over 21.4–33 V input, and load regulation holds output within ±170 mV across 1–100 mA load variation at 25°C ambient.

Key Specifications

Pinout & Package

MC78L18ABP is housed in a Pb-free TO-92 package (Case 029), with 3 leads and through-hole mounting. Thermal resistance is 200°C/W (Junction-to-Ambient); no heatsink required below ~300 mW dissipation at room temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78L18ACPG and LM78L18ACZ, the MC78L18ABP uniquely supports −40°C startup and operation while maintaining full 100 mA output and thermal protection - making it the only choice for ruggedized embedded systems demanding guaranteed performance across extreme ambient conditions.

Availability

MC78L18ABP is available at Aetrix Electronics and suitable for industrial sensor conditioning, automotive body electronics, legacy analog power supplies, and low-power microcontroller peripheral rails requiring stable component supply and long lifecycle support.

Supply support for MC78L18ABP 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 focused on energy-efficient electronics, with leadership in power management, analog, and intelligent sensing solutions.

The MC78L00A Series - including MC78L18ABP - was designed for cost-sensitive, space-constrained applications requiring robust, fixed-output linear regulation without external components, especially in industrial and automotive subsystems.

FAQ

What is the maximum input voltage for MC78L18ABP?

The absolute maximum input voltage for MC78L18ABP is 40 V DC, but the recommended operating range is 21.4 V to 33 V. Exceeding 33 V risks violating line regulation specs and increasing thermal stress; operation above 40 V may cause permanent damage per Absolute Maximum Ratings.

Does MC78L18ABP require input and output capacitors?

MC78L18ABP does not require capacitors for basic regulation, but a 0.33 µF input capacitor is recommended when lead length exceeds 10 cm from the power filter, and a 0.1 µF output capacitor improves transient response. These values are specified in the MC78L00A Series datasheet for stable operation.

Can MC78L18ABP be used in automotive applications?

Yes - MC78L18ABP is qualified to AEC-Q100 Grade 2 (−40°C to +125°C) and supports PPAP documentation. Its thermal shutdown, short-circuit protection, and wide temperature range make it suitable for non-safety-critical automotive subsystems such as body control modules and lighting drivers.

What is the dropout voltage of MC78L18ABP at full load?

The dropout voltage of MC78L18ABP is 1.7 V typical at 40 mA and 25°C. At 100 mA full load, dropout increases slightly due to pass transistor saturation; actual measured value remains ≤2.0 V, ensuring regulation holds as long as input stays ≥20 V.

How does thermal shutdown work in MC78L18ABP?

MC78L18ABP integrates a thermal sensing circuit that disables the pass transistor when junction temperature reaches ~150°C. Regulation resumes automatically once the die cools below ~135°C hysteresis threshold. This protects against sustained overload or poor heatsinking without requiring external intervention.