onsemi MC78M15CT

Overview

MC78M15CT from onsemi is a 15 V, 500 mA fixed-output positive linear voltage regulator in TO-220 package, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local on-card regulation. It delivers stable 15 V output across 17.5–30 V input range with ±3% initial accuracy and 2.0 V dropout at 350 mA.

For engineers reviewing the MC78M15CT datasheet, pinout, applications, or equivalent options, key selection criteria include output voltage tolerance (±3%), thermal protection behavior, load regulation (≤150 mV), ripple rejection (≥54 dB), and compatibility with standard TO-220 heatsinking solutions.

Technical Context

This three-terminal regulator uses a monolithic silicon design with internal pass transistor compensation to maintain safe operating area under varying load and input conditions. Its thermal shutdown activates at +150°C junction temperature, and short-circuit current limit is fixed at 350 mA typical.

The device operates without external components but benefits from input bypassing (≥0.33 µF) when connected via long traces or driving large capacitive loads. Dropout voltage remains constant at 2.0 V across temperature and load, enabling predictable minimum input requirements in industrial power rails.

Key Specifications

Pinout & Package

MC78M15CT uses the TO-220 package (Case 221AB), with heatsink surface electrically connected to Pin 2 (Ground). The plastic package has thermal resistance θ_JC = 5.0°C/W and θ_JA = 70°C/W in free air.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC7815CT and LM7815CT, MC78M15CT provides optimal balance of 500 mA capability, low quiescent current, and automotive-grade reliability-making it ideal for space-constrained, thermally managed 15 V rails where full 1.5 A is unnecessary.

Availability

MC78M15CT is available at Aetrix Electronics and suitable for industrial control power supplies, automotive body electronics, and test equipment signal conditioning requiring stable component supply and long-term lifecycle support.

Supply support for MC78M15CT 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MC78Mxx series was designed specifically for rugged, local voltage regulation in harsh environments-emphasizing thermal resilience, fault protection, and drop-in compatibility with legacy 78xx regulators.

FAQ

What is the maximum input voltage rating for MC78M15CT?

The MC78M15CT has an absolute maximum input voltage of 35 VDC. Operation above this level risks permanent damage. For reliable 15 V output, input should remain within 17.5–30 V per datasheet specifications to ensure proper regulation and thermal margin. Exceeding 35 V violates maximum ratings and voids reliability guarantees.

Does MC78M15CT require an input bypass capacitor?

Yes, MC78M15CT benefits from a ≥0.33 µF input bypass capacitor placed directly across Pins 1 and 2. This is especially critical when connected via long traces or driving large capacitive loads, as it stabilizes operation by suppressing high-frequency noise and transient response anomalies. Tantalum or ceramic capacitors with low ESR are recommended.

Can MC78M15CT be used in automotive applications?

MC78M15CT is rated for 0°C to +125°C junction temperature and is Pb-free, but it is not AEC-Q100 qualified. For automotive applications requiring qualification, consider NCV78M15BDTRKG (AEC-Q100 Grade 1, −40°C to +125°C) or MC78M15ABDTRKG. MC78M15CT remains suitable for under-hood-adjacent or cabin-mounted non-safety systems where full qualification is not mandated.

What is the thermal resistance of MC78M15CT in TO-220 package?

MC78M15CT in TO-220 (Case 221AB) has θ_JC = 5.0°C/W (junction-to-case) and θ_JA = 70°C/W (junction-to-air, free air). With a properly mounted heatsink (e.g., 20°C/W), total thermal resistance drops to ~25°C/W, enabling 500 mA operation at ambient temperatures up to +70°C without exceeding +150°C junction limit.

How does MC78M15CT handle short-circuit conditions?

MC78M15CT features internal short-circuit current limiting with a typical trip level of 350 mA. When output is shorted, the device limits current to protect itself and upstream circuitry. Combined with thermal shutdown at +150°C, this dual-protection scheme prevents latch-up or destruction during sustained faults. Recovery is automatic once fault is removed and junction temperature falls below shutdown threshold.