onsemi MC78M18CDTG

Overview

MC78M18CDTG from onsemi is a fixed-output 18 V, 500 mA positive linear voltage regulator in DPAK-3 package, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local regulation. It delivers stable output under load currents up to 500 mA with dropout voltage of 2.0 V and ±5% output voltage tolerance over temperature and line/load variations.

For engineers reviewing the MC78M18CDTG datasheet, pinout, applications, or equivalent options, key selection criteria include input voltage range (21–33 V), thermal resistance (θ_JA = 92°C/W, θ_JC = 5.0°C/W), ripple rejection (53 dB at 120 Hz), output noise (100 µV_RMS), and automotive-grade alternatives with AEC-Q100 qualification.

Technical Context

The MC78M18CDTG implements a monolithic series-pass regulator architecture with built-in protection circuitry: thermal overload shutdown activates at +150°C junction temperature, short-circuit current limit holds peak output at 350 mA, and safe-area compensation dynamically reduces short-circuit current as pass transistor V_CE increases. It requires no external components for basic operation.

Designed for local on-card regulation, it operates across an input range of 21–33 V DC to maintain 18 V ±5% output under 5–500 mA load, with line regulation ≤10 mV and load regulation ≤30 mV (5–500 mA). Quiescent current remains stable at 3.2–6.5 mA across operating conditions.

Key Specifications

Pinout & Package

DPAK-3 (Case 369C) surface-mount package with exposed thermal pad connected to Pin 2 (GND); footprint optimized for PCB copper area heat spreading per Figure 2 in datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78M18CDTG, NCV78M18BDTRKG adds automotive qualification and wider temperature range at identical performance, while MC78M18CTG trades surface-mount efficiency for mechanical robustness and easier thermal management via TO-220 heatsinking.

Availability

MC78M18CDTG is available at Aetrix Electronics and suitable for industrial power supplies, test equipment front-ends, and programmable logic controller I/O modules requiring stable component supply with RoHS-compliant packaging and consistent parametric performance.

Supply support for MC78M18CDTG 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 specializing in energy-efficient silicon solutions for automotive, industrial, cloud, and IoT applications.

The MC78Mxx series was designed as a cost-optimized, rugged fixed-output linear regulator family for local voltage regulation in space-constrained industrial and automotive subsystems, emphasizing reliability over programmability.

FAQ

What is the maximum input voltage rating for MC78M18CDTG?

The MC78M18CDTG has an absolute maximum input voltage rating of 40 V DC, though its recommended operating input range is 21–33 V DC to maintain 18 V output regulation across full load and temperature. Exceeding 40 V risks permanent damage even with thermal protection active.

Does MC78M18CDTG require an input bypass capacitor?

Yes, MC78M18CDTG requires a minimum 0.33 µF tantalum or low-ESR ceramic capacitor placed directly across Pins 1 and 2 (input-to-ground) to ensure stability, especially with long input traces or high-frequency noise. Omission may cause oscillation or poor transient response.

What is the thermal resistance and power dissipation limit of MC78M18CDTG in DPAK-3 package?

MC78M18CDTG in DPAK-3 has θ_JA = 92°C/W and θ_JC = 5.0°C/W. With a maximum junction temperature of +150°C and 25°C ambient, its usable power dissipation is limited to ~1.36 W without PCB copper heatsinking - scaling to ~5 W with adequate 2 oz. copper area per Figure 2.

Can MC78M18CDTG be used in automotive applications?

MC78M18CDTG is rated for 0°C to +125°C operation and is not AEC-Q100 qualified. For automotive use, select NCV78M18BDTRKG instead - it shares identical electrical specs but adds AEC-Q100 qualification, −40°C to +125°C range, and PPAP capability required for vehicle systems.

How does MC78M18CDTG handle short-circuit conditions?

MC78M18CDTG limits short-circuit output current to approximately 350 mA and activates thermal shutdown if junction temperature exceeds +150°C. Its safe-area compensation further reduces current as input-output differential increases, preventing second breakdown during sustained shorts.