onsemi MC78M09CTG

Overview

MC78M09CTG from onsemi is a 500 mA, fixed +9.0 V positive voltage regulator in TO-220 package with internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It delivers stable output under varying line (11.5–23 V input) and load (5–350 mA) conditions and is designed for local on-card regulation in industrial power supplies and embedded control systems.

For engineers reviewing the MC78M09CTG datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed ±5% output voltage accuracy at 25°C, 2.0 V dropout voltage, 56 dB ripple rejection at 120 Hz, 500 mA continuous output current capability, and operation across 0°C to +125°C junction temperature range.

Technical Context

The MC78M09CTG implements a monolithic three-terminal linear regulator architecture with an internal pass transistor featuring safe-area compensation to prevent secondary breakdown during overload. Its protection circuitry includes thermal shutdown triggered above +150°C junction temperature and foldback current limiting that reduces short-circuit current as input-to-output differential increases.

It operates without external components for basic regulation but requires input bypassing (≥0.33 µF) when connected via long traces or driving large capacitive loads. The device is not adjustable - output voltage is factory-trimmed and fixed at 9.0 V, with no feedback pin or external resistor network support.

Key Specifications

Pinout & Package

MC78M09CTG uses the TO-220 (Case 221AB) package with three leads and an electrically connected metal tab (Pin 2). The heatsink surface is internally tied to Pin 2 (Ground), requiring isolation if mounted to a conductive chassis.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78M09CDTRKG, MC78M09CTG offers easier mechanical heatsinking and higher creepage/clearance; compared with LM7809CT, it provides tighter tolerance, lower I_Q, and certified Pb-free construction - making it preferable for new industrial and automotive-adjacent designs.

Availability

MC78M09CTG is available at Aetrix Electronics and suitable for industrial power supplies, embedded control systems, and test equipment requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for MC78M09CTG 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 silicon and SiC solutions for automotive, industrial, cloud, and IoT applications.

The MC78Mxx series was designed as a robust, drop-in replacement for legacy 78xx regulators - optimized for local regulation in harsh environments with integrated protection and extended temperature operation.

FAQ

What is the maximum input voltage rating for MC78M09CTG?

The MC78M09CTG has an absolute maximum input voltage of 35 V DC. Operation above this level risks permanent damage. For reliable regulation at 9.0 V output, the recommended input range is 11.5 V to 23 V - ensuring sufficient headroom for the 2.0 V dropout while maintaining thermal safety under full 500 mA load.

Does MC78M09CTG require an input bypass capacitor?

Yes, MC78M09CTG requires an input bypass capacitor - typically ≥0.33 µF tantalum or ceramic - placed directly across Pins 1 and 2. This stabilizes the regulator under dynamic load changes and suppresses high-frequency noise from upstream sources. Omission may cause oscillation or poor transient response, especially with long input traces.

Can MC78M09CTG be used in automotive applications?

MC78M09CTG itself is rated for 0°C to +125°C junction temperature and is not AEC-Q100 qualified. For automotive use, select the NCV78M09BDTRKG variant - which shares identical electrical specs but includes PPAP documentation, extended −40°C to +125°C operation, and automotive-specific process controls verified per AEC-Q100.

What is the thermal resistance of MC78M09CTG in TO-220 package?

In TO-220 (Case 221AB), MC78M09CTG has θ_JC = 5.0°C/W (junction-to-case) and θ_JA = 70°C/W (junction-to-air, no heatsink). With a 20°C/W heatsink, total θ_JA drops to ~25°C/W - enabling 500 mA continuous operation at up to +75°C ambient when properly mounted with thermal compound and isolated hardware.

How does MC78M09CTG behave under short-circuit conditions?

Under output short-circuit, MC78M09CTG activates its internal foldback current limiter, reducing output current to ~350 mA typical (at 35 V input). Simultaneously, thermal shutdown engages if junction temperature exceeds +150°C. Once fault clears and temperature drops, the device automatically recovers - no latch or reset required.