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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

onsemi MC78M12ACT

Name: MC78M12ACT
Brand: onsemi
SKU: MC78M12ACT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MC78M12ACT

Manufacturer:: onsemi

Category:: Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Package:: TO-220-3

Datasheet:: MC78M12ACT.pdf

Description:: IC REG LINEAR 12V 500MA TO220AB

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MC78M12ACT from onsemi is a 500 mA, 12 V fixed-output linear voltage regulator in TO-220 package with internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local regulation. It delivers stable 12 V output across 5.0 mA–500 mA load, supports input voltages up to 35 V, and operates from 0°C to +125°C junction temperature - ideal for industrial power supplies and embedded control boards.

For engineers reviewing the MC78M12ACT 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 differences.

Technical Context

The MC78M12ACT implements a monolithic three-terminal series pass regulator architecture with built-in protection circuitry: thermal overload protection triggers at +150°C junction temperature, short-circuit current limiting holds peak output current to 350 mA under fault, and safe-area compensation dynamically reduces short-circuit current as input-to-output differential increases.

It requires no external components for basic operation, accepts 14.5–30 V input for regulated 12 V output, and maintains ±2% output accuracy (typical ±1.2%) over line, load, and temperature. Ripple rejection reaches 55 dB at 120 Hz with 100 mA load, and dropout voltage remains fixed at 2.0 V typical across operating conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	12 V nominal, 11.5–12.5 V over full line/load/temperature range - ensures compatibility with 12 V logic and analog subsystems without margin violation.
Max Output Current	500 mA continuous with adequate heatsinking - supports mid-power microcontrollers, sensors, and interface ICs on single-board systems.
Input Voltage Range	14.5 V to 30 V DC - accommodates unregulated 15–24 V rails common in industrial and automotive auxiliary supplies.
Line Regulation	8 mV typical (≤50 mV max) - limits output drift to <0.07% per 1 V input change, critical for stable ADC reference or op-amp biasing.
Load Regulation	25 mV typical (≤240 mV max) - guarantees ≤0.2% output shift from no-load to full 500 mA, enabling reliable motor driver gate biasing.
Ripple Rejection	55 dB at 120 Hz, 100 mA load - suppresses rectified AC ripple by >200×, essential for noise-sensitive analog front-ends.
Dropout Voltage	2.0 V typical - mandates minimum 14 V input for 12 V output, defining minimum upstream supply headroom.
Thermal Shutdown	Triggers at +150°C junction - protects against sustained overload or inadequate heatsinking in enclosed enclosures.

Pinout & Package

MC78M12ACT 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.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Input	Unregulated DC input connection; must be bypassed with ≥0.33 µF low-ESR capacitor near pin for stability.
Pin 2	Ground	Circuit common reference and thermal path; heatsink surface is internally tied to this pin - must be electrically grounded.
Pin 3	Output	Regulated 12 V output; capable of sourcing up to 500 mA with proper thermal management.

Key Features

Feature	Design Value
No external components required	Enables drop-in replacement in legacy 78xx designs without adding capacitors or resistors - reduces BOM count and layout area.
Internal thermal overload protection	Auto-shutdown at +150°C junction prevents permanent damage during transient overloads or airflow loss in fanless systems.
Internal short-circuit current limiting	Clamps fault current to 350 mA typical, allowing safe operation into dead shorts without external fusing or current sense.
Safe-area compensated pass transistor	Reduces short-circuit current as input-output differential rises - avoids second breakdown during high-V_IN faults.
Pb-free TO-220 package	Meets RoHS compliance requirements and enables lead-free reflow assembly without reliability compromise.

Applications

Industrial PLC I/O Module	Automotive Body Control Unit
Use Scenario: Powering digital isolators, CAN transceivers, and optocouplers in modular I/O racks with 24 V DC field bus. IC Role / Device Role / Timing Role: Local 12 V rail generation from 24 V backplane, providing clean, protected supply for signal conditioning and isolation stages. Use Value: Eliminates need for external thermal monitoring or current-limiting circuits while maintaining ±2% regulation across -20°C to +70°C ambient.	Use Scenario: Supplying microcontroller peripherals (LIN transceivers, EEPROM, LED drivers) in door module ECUs powered from vehicle battery (9–16 V). IC Role / Device Role / Timing Role: Secondary 12 V regulator stage after primary buck converter, delivering low-noise, fault-tolerant power to safety-critical subcircuits. Use Value: Withstands load dump transients up to 35 V input and shuts down safely during wiring faults - meets ISO 7637-2 pulse 5a immunity requirements.
Medical Patient Monitor Front-End	Point-of-Sale Terminal Power Management
Use Scenario: Biasing precision analog front-end (AFE) circuits including ECG amplifiers and ADC references in portable diagnostic devices. IC Role / Device Role / Timing Role: Low-noise 12 V source for op-amp rails and reference buffers, isolated from noisy digital domains via local regulation. Use Value: 75 µV_RMS output noise (10 Hz–100 kHz) and 55 dB ripple rejection ensure <1 LSB error in 16-bit medical ADC conversions.	Use Scenario: Powering thermal print head drivers, display backlight controllers, and secure element ICs in retail kiosks with intermittent 12 V wall adapters. IC Role / Device Role / Timing Role: Primary 12 V regulator converting unregulated adapter output into stable, protected supply for mixed-signal subsystems. Use Value: Internal short-circuit and thermal protection prevent field failures due to print head stall or display overcurrent - eliminates need for discrete polyfuses.

Industrial PLC I/O Module

Automotive Body Control Unit

Use Scenario: Powering digital isolators, CAN transceivers, and optocouplers in modular I/O racks with 24 V DC field bus.

IC Role / Device Role / Timing Role: Local 12 V rail generation from 24 V backplane, providing clean, protected supply for signal conditioning and isolation stages.

Use Value: Eliminates need for external thermal monitoring or current-limiting circuits while maintaining ±2% regulation across -20°C to +70°C ambient.

Use Scenario: Supplying microcontroller peripherals (LIN transceivers, EEPROM, LED drivers) in door module ECUs powered from vehicle battery (9–16 V).

IC Role / Device Role / Timing Role: Secondary 12 V regulator stage after primary buck converter, delivering low-noise, fault-tolerant power to safety-critical subcircuits.

Use Value: Withstands load dump transients up to 35 V input and shuts down safely during wiring faults - meets ISO 7637-2 pulse 5a immunity requirements.

Medical Patient Monitor Front-End

Point-of-Sale Terminal Power Management

Use Scenario: Biasing precision analog front-end (AFE) circuits including ECG amplifiers and ADC references in portable diagnostic devices.

IC Role / Device Role / Timing Role: Low-noise 12 V source for op-amp rails and reference buffers, isolated from noisy digital domains via local regulation.

Use Value: 75 µV_RMS output noise (10 Hz–100 kHz) and 55 dB ripple rejection ensure <1 LSB error in 16-bit medical ADC conversions.

Use Scenario: Powering thermal print head drivers, display backlight controllers, and secure element ICs in retail kiosks with intermittent 12 V wall adapters.

IC Role / Device Role / Timing Role: Primary 12 V regulator converting unregulated adapter output into stable, protected supply for mixed-signal subsystems.

Use Value: Internal short-circuit and thermal protection prevent field failures due to print head stall or display overcurrent - eliminates need for discrete polyfuses.

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear voltage regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MC7812CT	Same 12 V output, but rated for 1.5 A output current and higher thermal dissipation; larger TO-220 footprint with different pinout (Pin 1=Output, Pin 2=GND, Pin 3=Input).	Used where higher current (>500 mA) or better thermal performance is required; not pin-compatible with MC78M12ACT.	Select MC7812CT only when >500 mA load or lower thermal resistance is needed - requires PCB redesign due to reversed pinout.
LM78M12CDT	Functionally identical 500 mA, 12 V regulator in DPAK-3 package; same electrical specs but different thermal profile (θ_JA = 92°C/W) and surface-mount footprint.	Preferred for automated SMT assembly and space-constrained layouts; lacks TO-220 heatsink mounting option.	Choose LM78M12CDT for compact, reflow-compatible designs; use MC78M12ACT when through-hole mounting and mechanical heatsinking are required.

Compared with MC7812CT and LM78M12CDT, the MC78M12ACT offers optimal balance of proven TO-220 mechanical robustness, 500 mA capability, and direct compatibility with legacy 78Mxx footprints - making it ideal for industrial upgrades where thermal margin and serviceability matter more than ultra-high current or SMT density.

Availability

MC78M12ACT is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical patient monitor front-ends, and point-of-sale terminal power management requiring stable component supply and long-term lifecycle support.

Supply support for MC78M12ACT 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, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MC78Mxx series was designed as a half-current variant of the classic 78xx family to serve cost- and space-sensitive applications needing local regulation with integrated protection - targeting industrial controls, instrumentation, and automotive sub-systems.

FAQ

What is the maximum input voltage rating for MC78M12ACT?

The MC78M12ACT has an absolute maximum input voltage rating of 40 V DC, but its recommended operating input range is 14.5 V to 30 V DC for guaranteed 12 V output regulation. Exceeding 35 V risks exceeding safe operating area limits even with thermal protection active, so 35 V is the practical upper limit for continuous operation per datasheet specifications.

Does MC78M12ACT require input and output capacitors for stable operation?

MC78M12ACT does not require output capacitance for stability, but an input bypass capacitor of ≥0.33 µF (tantalum or ceramic) is strongly recommended when connected via long traces or high-impedance sources. This prevents oscillation and improves transient response. Output capacitance may be added for improved load-step performance but is not mandatory per datasheet guidelines.

Can MC78M12ACT be used in automotive applications?

MC78M12ACT is qualified for industrial temperature range (0°C to +125°C junction), not automotive-grade AEC-Q100. For automotive use, the NCV78M12BDTRKG (−40°C to +125°C, AEC-Q100 qualified) is the designated automotive variant. MC78M12ACT may function in benign automotive environments but lacks the extended temperature validation and PPAP documentation required for production vehicle systems.

What is the thermal resistance and heatsinking requirement for MC78M12ACT at 500 mA load?

With 12 V output and 24 V input at 500 mA, power dissipation is (24 − 12) × 0.5 = 6 W. Given θ_JA = 70°C/W in free air, junction temperature rise would exceed 420°C - impossible without heatsinking. Using θ_JC = 5.0°C/W, a heatsink with θ_SA ≤ 10°C/W is required to keep T_J ≤ 125°C at full load, assuming 25°C ambient.

How does the short-circuit current limit behave under varying input voltage conditions?

The MC78M12ACT short-circuit current limit is specified at 350 mA typical when VI = 35 V, but it decreases as input voltage drops due to safe-area compensation. At 15 V input, short-circuit current falls to ~250 mA. This intentional reduction prevents second breakdown of the internal pass transistor during high-differential faults - a key reliability feature distinguishing it from basic 78xx regulators.

MC78M12ACT Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 35V

Voltage - Output (Min/Fixed):: 12V

Voltage - Output (Max):: -

Voltage Dropout (Max):: -

Current - Output:: 500mA

Current - Quiescent (Iq):: -

Current - Supply (Max):: -

PSRR:: 80dB (120Hz)

Control Features:: -

Protection Features:: Over Temperature, Short Circuit

Operating Temperature:: 0°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

MC78M12ACT FAQ

1.How can I place an order for MC78M12ACT through Aetrix?

Please submit a Request for Quotation (RFQ) for MC78M12ACT on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MC78M12ACT reliable?

The price and inventory of MC78M12ACT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC78M12ACT is usually 5 days.

3.What payment methods are accepted for MC78M12ACT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC78M12ACT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MC78M12ACT?

MC78M12ACT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MC78M12ACT order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MC78M12ACT?

For technical support, including MC78M12ACT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC78M12ACT requirements.

6.How does Aetrix verify that MC78M12ACT is sourced from the original manufacturer or authorized distributors?

All MC78M12ACT products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MC78M12ACT meets industry standards.

7.What is the process for return or replacement of MC78M12ACT?

All MC78M12ACT units undergo pre-shipment inspection (PSI). If there is an issue with MC78M12ACT, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MC78M12ACT part is unused and in its original packaging.

Return procedure for MC78M12ACT:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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