onsemi MC78M18CDTRK

Overview

MC78M18CDTRK from onsemi is a 500 mA, fixed +18 V positive linear voltage regulator in DPAK-3 (TO-252) package, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local on-card regulation. It delivers stable output under load currents up to 500 mA with ≤18.9 V variation across input range (21–33 V) and operating temperature (0°C to +125°C), commonly used in industrial power supplies and embedded control subsystems.

For engineers reviewing the MC78M18CDTRK datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (2.0 V typ), ripple rejection (53 dB min at 120 Hz), output noise (100 µV rms), load regulation (360 mV max), and thermal performance in surface-mount PCB layouts requiring minimal heatsinking.

Technical Context

The MC78M18CDTRK implements a monolithic three-terminal series pass regulator architecture with built-in protection circuitry: thermal overload shutdown activates at ~150°C junction temperature, and short-circuit current limit holds peak output at 350 mA (typ) when VI = 35 V. Its internal safe-area compensation dynamically reduces short-circuit current as V_IN−V_OUT increases, preventing second breakdown of the pass transistor.

Designed for fixed-output operation without external components, it operates with input voltages from 21 V to 33 V (for 18 V output), maintains ±0.3 mV/°C average temperature coefficient, and achieves 700 mA peak output current capability at TJ = 25°C - exceeding its rated 500 mA continuous output due to internal current boosting design.

Key Specifications

Pinout & Package

DPAK-3 (TO-252) surface-mount package with exposed thermal pad (pin 2 connected to GND). Pin 1 is Input, Pin 2 is Ground (and thermal tab), Pin 3 is Output. Requires minimum 2.0 oz. copper area ≥25 mm² per side for 500 mA operation at TA = 50°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M18CDT/NOPB, MC78M18CDTRK offers 8 dB higher ripple rejection and tighter load regulation; versus NCV78M18BDTRKG, it trades automotive qualification for lower cost and simplified procurement in non-automotive applications.

Availability

MC78M18CDTRK is available at Aetrix Electronics and suitable for industrial power supplies, programmable logic controller (PLC) I/O cards, and test & measurement equipment requiring stable component supply with consistent lead times and volume pricing.

Supply support for MC78M18CDTRK 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 power management, analog, and sensing technologies for automotive, industrial, and cloud power applications.

The MC78Mxx series was designed as a half-current derivative of the classic 78xx family, targeting space-constrained PCBs needing reliable, low-cost, fixed-output regulation without external components - especially in industrial control and instrumentation.

FAQ

What is the maximum input voltage for the MC78M18CDTRK?

The MC78M18CDTRK supports a maximum input voltage of 35 V DC, as specified in the Absolute Maximum Ratings table. Operation above this level risks permanent damage. For reliable 18 V output, the recommended input range is 21 V to 33 V - ensuring sufficient headroom while staying within safe dissipation limits under full 500 mA load.

Does the MC78M18CDTRK require an input bypass capacitor?

Yes, the MC78M18CDTRK requires a minimum 0.33 µF low-ESR capacitor (e.g., tantalum or ceramic) placed directly across pins 1 (Input) and 2 (GND). This stabilizes the regulator under fast load transients and suppresses high-frequency noise from upstream sources. Without it, oscillation or voltage overshoot may occur, especially with long input traces or switching supply inputs.

Can the MC78M18CDTRK be used in automotive applications?

The MC78M18CDTRK is rated for 0°C to +125°C junction temperature and is not AEC-Q100 qualified. For automotive applications requiring qualification, use the NCV78M18BDTRKG variant instead. The MC78M18CDTRK may be deployed in non-safety-critical, cabin-mounted industrial or aftermarket devices where extended temperature validation is not mandated.

What is the thermal resistance of the MC78M18CDTRK in DPAK-3 package?

The MC78M18CDTRK in DPAK-3 (Case 369C) has a junction-to-case thermal resistance (θ_JC) of 5.0°C/W and a junction-to-air thermal resistance (θ_JA) of 92°C/W in free air. With a 25 mm² 2.0 oz. copper pad on one side, θ_JA improves to ~50°C/W - enabling 500 mA continuous operation at ambient temperatures up to 50°C without additional heatsinking.

How does the MC78M18CDTRK handle short-circuit conditions?

The MC78M18CDTRK limits short-circuit output current to 350 mA (typical) when input voltage is 35 V, and activates thermal shutdown if junction temperature exceeds ~150°C. Its safe-area compensation reduces this current as V_IN−V_OUT increases, preventing destructive second breakdown. Recovery is automatic once fault clears and temperature drops below shutdown threshold.