onsemi MC78M15CDT

Overview

MC78M15CDT from onsemi is a 500 mA, 15 V fixed-output linear voltage regulator in DPAK-3 (TO-252) package, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local regulation. It delivers stable 15 V output across 5.0 mA–500 mA load with ±3% initial accuracy (14.4–15.6 V at 25°C), dropout voltage of 2.0 V, and operates from 17.5–30 V input-ideal for industrial power supplies and embedded control rails.

For engineers reviewing the MC78M15CDT datasheet, pinout, applications, or equivalent options, key selection criteria include its 15 V fixed output, 500 mA continuous current capability, DPAK-3 thermal performance (θ_JA = 92°C/W, θ_JC = 5.0°C/W), and automotive-grade alternatives with extended temperature range.

Technical Context

The MC78M15CDT implements a monolithic three-terminal series pass architecture with built-in protection circuitry: thermal overload shutdown triggers at +150°C junction temperature, short-circuit current limit holds peak output at 350 mA (typical), and safe-area compensation dynamically reduces short-circuit current as V_IN–V_OUT increases. It requires no external components for basic operation but benefits from 0.33 µF input bypass capacitance for stability under high-frequency transients.

Its electrical behavior is defined over 0°C to +125°C operating junction range, with line regulation ≤10 mV (17.5–30 V input), load regulation ≤25 mV (5–500 mA), ripple rejection ≥54 dB at 120 Hz, and output noise voltage ≤90 µV_RMS (10 Hz–100 kHz). Quiescent current remains stable at 3.2–6.0 mA across full input and load conditions.

Key Specifications

Pinout & Package

DPAK-3 (TO-252) package with exposed thermal pad (pin 2 connected to GND); compact 6.10 × 6.54 × 2.28 mm footprint optimized for surface-mount power regulation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78M15CDT, MC78M15BDTRKG extends cold-temperature operation without altering thermal or electrical performance, while NCV78M15BDTRKG adds automotive qualification overhead-neither offers pin-to-pin or functional upgrades beyond temperature and certification scope.

Availability

MC78M15CDT is available at Aetrix Electronics and suitable for industrial PLC power rails, medical device analog supplies, and test equipment biasing requiring stable component supply and long-term manufacturability.

Supply support for MC78M15CDT 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 solutions for automotive, industrial, and cloud infrastructure markets.

The MC78Mxx series was designed as a cost-optimized, rugged 500 mA fixed-output linear regulator family for local voltage regulation in space-constrained, thermally demanding environments-emphasizing reliability over programmability.

FAQ

What is the maximum input voltage for MC78M15CDT?

The MC78M15CDT supports a maximum input voltage of 40 V DC under transient conditions, with continuous operation rated up to 35 V DC. Its absolute maximum input rating is 40 V, but sustained operation above 30 V increases thermal stress and reduces safe operating area margin-designs should maintain input within 17.5–30 V for optimal 500 mA output capability and thermal performance.

Does MC78M15CDT require an input bypass capacitor?

Yes, MC78M15CDT requires a minimum 0.33 µF low-ESR input bypass capacitor (e.g., tantalum or ceramic) placed directly across pins 1 and 2. This capacitor stabilizes the regulator under fast load transients and suppresses high-frequency noise from upstream sources; omission risks oscillation or erratic dropout behavior, especially with >10 cm input trace lengths or high-impedance supplies.

What is the thermal resistance of MC78M15CDT in its DPAK-3 package?

The MC78M15CDT in DPAK-3 (Case 369C) has a junction-to-air thermal resistance (θ_JA) of 92°C/W and junction-to-case (θ_JC) of 5.0°C/W. These values assume standard JEDEC 2-layer PCB layout with 1 in² (645 mm²) 2 oz. copper pour connected to pin 2 (GND/tab); actual θ_JA improves with larger copper areas or external heatsinking, enabling full 500 mA output at ambient temperatures up to +50°C.

Can MC78M15CDT be used in automotive applications?

MC78M15CDT is rated for 0°C to +125°C junction temperature and meets Pb-free RoHS requirements, but it is not AEC-Q100 qualified. For non-safety-critical automotive cabin applications with controlled ambient (e.g., infotainment USB hubs), it may function-but onsemi recommends MC78M15BDTRKG (−40°C to +125°C) or NCV78M15BDTRKG (AEC-Q100 qualified) for under-hood or production automotive use where extended temperature and qualification are mandatory.

How does the short-circuit protection work in MC78M15CDT?

MC78M15CDT employs foldback current limiting: during output short-circuit, its internal circuitry reduces output current to ~350 mA (typical) while simultaneously lowering output voltage toward zero. This limits power dissipation in the pass transistor, preventing thermal runaway. Once the short is removed, the device automatically recovers normal 15 V regulation without requiring power-cycle or external reset-enabling robust operation in field-deployed equipment.