onsemi MC78M08BDTG

Overview

MC78M08BDTG from onsemi is a 500 mA, fixed +8.0 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 regulation. It delivers stable output across −40°C to +125°C ambient, with ±3% output voltage tolerance at 25°C and dropout voltage of 2.0 V - ideal for industrial power rails and automotive subsystems requiring robust, low-component-count DC/DC conversion.

For engineers reviewing the MC78M08BDTG datasheet, pinout, applications, or equivalent options, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation guidance, and two confirmed alternative parts with documented functional and application-level differences.

Technical Context

The MC78M08BDTG implements a monolithic series pass transistor architecture with integrated protection circuitry: thermal overload detection triggers shutdown before junction temperature exceeds +150°C, while short-circuit current limiting caps peak output at 350 mA under fault conditions. Safe-area compensation dynamically reduces short-circuit current as input-output differential increases, preventing secondary breakdown.

It operates without external components for basic regulation but requires an input bypass capacitor (≥0.33 µF) when connected via long traces or driving large capacitive loads. Ripple rejection reaches 56 dB at 120 Hz (100 mA load), and output noise is 52 µV_RMS (10 Hz–100 kHz), making it suitable for analog-sensitive subsystems where switching noise must be avoided.

Key Specifications

Pinout & Package

DPAK-3 (TO-252) surface-mount package with exposed thermal pad (pin 2 connected to GND). Heatsink surface is electrically tied to pin 2 (GND), enabling direct PCB copper pour for thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed positive voltage regulation applications.

Compared with MC78M08CDTRKG, the MC78M08BDTG trades ±2% accuracy for guaranteed −40°C operation - critical for cold-climate deployment. Versus NCV78M08BDTRKG, it lacks AEC-Q100 certification and automotive change control, making it suitable for industrial and medical applications where qualification overhead is unnecessary.

Availability

MC78M08BDTG is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLCs, medical sensor interfaces, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MC78M08BDTG 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 infrastructure markets.

The MC78M00 series was designed as a rugged, drop-in replacement for legacy 78xx regulators - optimized for local on-board regulation in harsh environments where thermal resilience, fault tolerance, and minimal external components are essential.

FAQ

What is the maximum input voltage rating for the MC78M08BDTG?

The MC78M08BDTG has an absolute maximum input voltage of 40 Vdc (for 20–24 V-rated versions) per its datasheet. However, for reliable operation at full 500 mA load, input should remain ≤23 Vdc to stay within safe power dissipation limits and avoid triggering thermal shutdown. Exceeding 35 Vdc risks permanent damage even under no-load conditions.

Does the MC78M08BDTG require an input bypass capacitor?

Yes - the MC78M08BDTG requires a minimum 0.33 µF input bypass capacitor (tantalum, ceramic, or film) placed directly across pins 1 and 2. This stabilizes operation under high-frequency noise or long trace inductance, preventing oscillation. Without it, the MC78M08BDTG may exhibit instability or increased output ripple, especially when fed from switch-mode supplies.

Can the MC78M08BDTG be used in parallel to increase output current?

No - the MC78M08BDTG is not designed for parallel operation. Its output voltage tolerance (±3%) and lack of current-sharing features mean paralleling units will cause unequal current distribution, thermal runaway, and premature failure. For >500 mA, use a single higher-current regulator or implement external current boosting with a PNP transistor as documented in the datasheet.

What is the thermal resistance (θ_JA) of the MC78M08BDTG in standard PCB layout?

The MC78M08BDTG in DPAK-3 package has a typical junction-to-air thermal resistance (θ_JA) of 92°C/W with no PCB copper heatsinking. With a 1-inch² 2-oz copper pad connected to pin 2 (GND), θ_JA improves to ~50°C/W. Full thermal performance data is shown in Figure 2 of the datasheet, correlating copper area to achievable power dissipation at ambient temperatures.

Is the MC78M08BDTG pin-compatible with older TO-220 versions like MC78M08BTG?

No - the MC78M08BDTG uses DPAK-3 (TO-252) packaging with 3 leads in a surface-mount configuration, while MC78M08BTG uses TO-220 with 3 through-hole leads and different mechanical dimensions. Though both share identical pin numbering (1=IN, 2=GND, 3=OUT), their footprints, thermal paths, and mounting methods are incompatible without PCB redesign.