onsemi MC78M05BDT

Overview

MC78M05BDT from onsemi is a 5.0 V, 500 mA fixed-output linear voltage regulator in DPAK-3 (TO-252) package with ±2% output accuracy, thermal shutdown, internal short-circuit current limiting, and safe-area compensation for rugged local on-card regulation. It operates across −40°C to +125°C and delivers stable 5 V power for microcontroller peripherals, sensor interfaces, and industrial control logic.

For engineers reviewing the MC78M05BDT datasheet, pinout, applications, or equivalent options, this page provides verified electrical specs, thermal performance data, PCB layout guidance for DPAK-3 copper area, and validated automotive-grade alternatives compatible with AEC-Q100 requirements.

Technical Context

The MC78M05BDT implements a monolithic three-terminal series pass regulator architecture with built-in thermal overload protection and foldback current limiting. Its internal safe-area compensation dynamically reduces short-circuit current as input-to-output differential increases, preventing secondary breakdown of the pass transistor under fault conditions.

Designed for local regulation, it requires no external components for basic operation but benefits from ≥0.33 µF input bypass capacitance when connected via long traces or driving large capacitive loads. Dropout voltage remains ≤2.0 V at 500 mA, enabling use with 7–35 V unregulated inputs while maintaining regulation.

Key Specifications

Pinout & Package

DPAK-3 (TO-252) plastic surface-mount package with exposed thermal pad (Pin 2), 6.10 mm × 6.54 mm footprint, and 2.29 mm lead pitch. Heatsink surface electrically connected to Pin 2 (Ground).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78M05CDTRKG, the MC78M05BDT offers extended −40°C startup capability critical for outdoor or automotive applications; versus NCV78M05BDTRKG, it lacks formal AEC-Q100 certification but shares identical silicon and thermal performance - making it suitable for pre-qualification prototyping or non-safety automotive subsystems.

Availability

MC78M05BDT is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical instrumentation requiring stable component supply, long-term lifecycle support, and Pb-free compliance.

Supply support for MC78M05BDT 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, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MC78M00 series was designed as a rugged, drop-in replacement for legacy 78xx regulators - delivering enhanced thermal protection, tighter tolerances, and extended temperature operation for mission-critical embedded systems.

FAQ

What is the maximum input voltage rating for the MC78M05BDT?

The MC78M05BDT has an absolute maximum input voltage of 40 V DC under transient conditions, but its recommended operating range is 7.0 V to 35 V DC. Exceeding 35 V continuously risks exceeding safe power dissipation limits, especially at high ambient temperatures or without sufficient PCB copper area for heat spreading. Always verify thermal design using the DPAK-3 θ_JA = 92°C/W (free air) and θ_JC = 5.0°C/W values from the datasheet.

Does the MC78M05BDT require an input bypass capacitor?

Yes, the MC78M05BDT requires a minimum 0.33 µF input bypass capacitor placed directly across Pins 1 and 2, with shortest possible leads. This capacitor stabilizes operation under high-frequency noise, long trace inductance, or large output load capacitance. Tantalum, ceramic, or low-ESR polymer capacitors are preferred; electrolytic types may be used if ESR is ≤1 Ω. Omitting this capacitor can cause oscillation or regulation failure.

What is the thermal resistance and how does it affect MC78M05BDT performance?

The MC78M05BDT in DPAK-3 has θ_JA = 92°C/W (free air) and θ_JC = 5.0°C/W. This means junction temperature rises 92°C per watt dissipated without PCB copper, but only 5°C per watt from junction to case - so effective heatsinking via the exposed pad is essential. For example, at 500 mA and 12 V input (7 V dropout), power dissipation is 3.5 W; with 100 mm² copper, θ_JA drops to ~50°C/W, keeping T_J within 125°C limit at 50°C ambient.

Can the MC78M05BDT be used in automotive applications?

Yes, the MC78M05BDT is rated for −40°C to +125°C junction temperature and is widely used in non-safety automotive subsystems such as infotainment power rails, lighting controls, and HVAC modules. While it is not AEC-Q100 qualified itself, its electrical and thermal specs match those of the automotive-grade NCV78M05BDTRKG - making it suitable for prototyping, aftermarket modules, or Tier-2 applications where formal qualification is not mandated.

How does the MC78M05BDT handle short-circuit conditions?

The MC78M05BDT features internal foldback current limiting that reduces short-circuit current to ≤350 mA when input voltage is 35 V, plus thermal shutdown that disables output above +150°C junction temperature. During sustained short-circuit, the device cycles between current limit and thermal shutdown to prevent destruction. Recovery is automatic once fault clears and junction temperature falls below thermal trip threshold - no manual reset required.