onsemi MC79L18ACP

Overview

MC79L18ACP from ON Semiconductor is a three-terminal, fixed-output, negative-voltage linear regulator delivering −18 V at up to 100 mA. It features internal short-circuit current limiting, thermal overload protection, and requires no external components for basic operation. It is used in low-power analog circuitry, sensor biasing, and dual-rail op-amp supplies where stable negative rail generation is needed.

For engineers reviewing the MC79L18ACP datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (1.7 V at 40 mA), output voltage tolerance (±3.9% at +25°C), thermal shutdown behavior, and TO-92 package compatibility with legacy through-hole designs.

Technical Context

The MC79L18ACP implements a monolithic bipolar linear regulation architecture with built-in foldback current limiting and thermal shutdown circuitry. Its input voltage range supports −20.7 V to −33 V under specified load conditions, and it maintains regulation down to 1.7 V differential between input and output.

It operates across 0°C to +125°C junction temperature range and exhibits 150 µV RMS output noise (10 Hz–100 kHz) and 33–48 dB ripple rejection at 120 Hz. No external compensation capacitors are required for stability in most applications, though input bypassing with ≥0.33 µF is recommended for long trace runs.

Key Specifications

Pinout & Package

MC79L18ACP is supplied in a TO-92 (Case 29) plastic package with straight leads, Pb-free finish, and through-hole mounting. The package has a thermal resistance of 160°C/W (junction-to-ambient) at TA = +25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7918ACZ and MC79M18CP, the MC79L18ACP offers the lowest BOM cost and smallest footprint for ≤100 mA applications, while maintaining identical functional regulation behavior and pin-compatible layout within TO-92 constraints.

Availability

MC79L18ACP is available at Aetrix Electronics and suitable for op-amp biasing, sensor excitation, and industrial I/O module replacement requiring stable component supply, RoHS-compliant packaging, and through-hole manufacturability.

Supply support for MC79L18ACP 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

ON Semiconductor is a global semiconductor manufacturer specializing in power management, analog, sensor, and logic devices for automotive, industrial, and consumer applications.

The MC79L00A Series was designed specifically for cost-sensitive, low-current negative voltage regulation in legacy and space-constrained systems, emphasizing ruggedness, simplicity, and drop-in replaceability.

FAQ

What is the maximum input voltage for MC79L18ACP?

The MC79L18ACP supports a maximum input voltage of −33 V under specified operating conditions. This rating applies when the device is delivering up to 40 mA at +25°C ambient. Exceeding −33 V risks exceeding absolute maximum junction temperature or triggering premature thermal shutdown, especially at elevated ambient temperatures or higher load currents. Always refer to the derating curve in Figure 8 of the datasheet for safe operation across temperature.

Does MC79L18ACP require input or output capacitors?

The MC79L18ACP does not require external capacitors for basic regulation stability, but ON Semiconductor recommends a 0.33 µF input bypass capacitor (tantalum or low-ESR ceramic) placed close to the input pin, especially when connected via long traces to the power supply filter. An optional 0.1 µF output capacitor improves transient response and noise suppression. These values are validated in the standard application circuit (Figure 3) and referenced in the Applications Information section.

What is the output voltage tolerance of MC79L18ACP over temperature and load?

The MC79L18ACP guarantees an output voltage of −17.1 V to −18.9 V across its full operating range: 0°C to +125°C junction temperature and 1.0 mA to 40 mA load current. At +25°C and 40 mA, the typical output is −18.0 V with a min/max spread of −17.3 V to −18.7 V. This ±3.9% tolerance ensures predictable performance in analog circuits where rail accuracy directly impacts gain and offset calibration.

Can MC79L18ACP be used in automotive applications?

The MC79L18ACP (suffix "C") is rated for 0°C to +125°C junction temperature, making it suitable for under-hood or cabin-located non-safety-critical automotive subsystems such as infotainment power rails or sensor interfaces. However, it is not qualified to AEC-Q100 standards. For automotive-grade reliability, ON Semiconductor offers the "AB" variant (e.g., MC79L18ABPG), which undergoes extended temperature testing (−40°C to +125°C) and additional qualification per automotive requirements.

How does thermal shutdown work in MC79L18ACP?

The MC79L18ACP integrates a thermal shutdown circuit that disables the output when the silicon junction temperature reaches approximately +150°C. Once triggered, regulation ceases until the die cools sufficiently-typically by several degrees below the trip point-to allow automatic recovery. This behavior is fully characterized in the Maximum Ratings table and Typical Characteristics (Figure 5), and protects against permanent damage during sustained overload, poor heatsinking, or ambient temperature excursions.