onsemi MC7818CT

Overview

MC7818CT from onsemi is a fixed-output, 18 V, 1.0 A positive linear voltage regulator in TO-220 package with internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It delivers stable 18 V output across 5 mA–1.0 A load range with ≤2.0 V dropout at full load, supporting local regulation in industrial power supplies, motor control logic, and embedded system rails.

For engineers reviewing the MC7818CT datasheet, pinout, applications, or equivalent options, this page provides verified specifications, thermal performance data, real-world stability guidance (including input/output capacitor requirements), and validated alternative parts for design continuity and supply chain resilience.

Technical Context

The MC7818CT implements a monolithic series-pass transistor architecture with built-in protection circuitry: thermal overload detection triggers shutdown above +150°C junction temperature, while short-circuit current limiting holds peak output at 0.2 A under 35 V input. Safe-area compensation dynamically reduces short-circuit current as pass transistor V_CE increases, preventing second breakdown.

It operates with a minimum input-to-output differential of 2.0 V at 1.0 A and maintains ±1.5% output voltage tolerance over temperature (−40°C to +125°C) and line/load variations. Ripple rejection is 53–57 dB at 120 Hz, and output noise is 10 µV/V RMS (10 Hz–100 kHz), confirming suitability for analog-sensitive subsystems requiring low-noise DC rails.

Key Specifications

Pinout & Package

MC7818CT uses the industry-standard TO-220 package (Case 221AB), with the metal tab electrically connected to Pin 2 (Ground). The package requires mechanical mounting to a heatsink for operation above ~350 mW dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7818CT, MC7818CT offers superior ripple rejection and lower quiescent current, improving noise performance and standby efficiency; versus NCV7818CT, it trades automotive qualification for lower cost and broader commercial availability, making it optimal for industrial and test equipment where AEC-Q100 is unnecessary.

Availability

MC7818CT is available at Aetrix Electronics and suitable for industrial power supplies, motor control logic rails, and embedded system auxiliary rails requiring stable component supply, long-term BOM continuity, and traceable sourcing.

Supply support for MC7818CT 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 is a global semiconductor supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.

The MC7800 series was designed as a rugged, drop-in fixed-voltage regulator family for local board-level regulation - prioritizing reliability, integrated protection, and ease of use in harsh environments.

FAQ

What is the minimum input voltage required for MC7818CT to maintain regulation at 1.0 A?

The MC7818CT requires a minimum input voltage of 20.0 V DC to sustain 18.0 V output at 1.0 A load, based on its maximum 2.0 V dropout specification at TJ = 25°C. At elevated temperatures or higher loads, design margin should increase input to ≥21 V to ensure regulation across all operating conditions. Input ripple must also be accounted for - the valley of the ripple waveform must remain ≥20.0 V.

Does MC7818CT require input and output capacitors, and what values are recommended?

Yes - MC7818CT requires a minimum 0.33 µF input capacitor (tantalum, ceramic, or low-ESR film) placed directly across Pins 1 and 2 to suppress high-frequency noise and prevent oscillation. An output capacitor (≥0.1 µF, preferably 1–10 µF aluminum or tantalum) is not mandatory for stability but significantly improves transient response. Values below 0.1 µF may cause instability under dynamic load steps.

How does thermal shutdown work in MC7818CT, and can it be manually reset?

MC7818CT features fully autonomous thermal shutdown: when junction temperature reaches +150°C, internal circuitry disables the pass transistor until TJ falls below ~135°C, at which point regulation resumes automatically. No external reset signal or power cycle is needed. This behavior is intrinsic to the silicon design and cannot be disabled or externally controlled.

What is the short-circuit current limit of MC7818CT, and how does it behave under sustained fault?

Under short-circuit conditions at VIN = 35 V, MC7818CT limits output current to approximately 0.2 A. This limit is not fixed - it decreases as input voltage rises due to safe-area compensation, protecting the pass transistor from second breakdown. During sustained short, the device alternates between current limiting and thermal shutdown, resulting in pulsed output rather than continuous conduction.

Is MC7818CT compatible with lead-free soldering processes?

Yes - MC7818CT is Pb-free and RoHS-compliant, qualified for standard lead-free reflow profiles (JEDEC J-STD-020D). Its TO-220 package withstands peak temperatures up to 260°C for 30 seconds. Thermal mass requires careful profiling to avoid overheating the die during soldering; preheating and controlled ramp rates are recommended to prevent internal stress.