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onsemi MC78M12BT
- Part No.:
- MC78M12BT
- Manufacturer:
- onsemi
- Package:
- TO-220-3
- Datasheet:
-
MC78M12BT.pdf
- Description:
- IC REG LINEAR 12V 500MA TO220AB
- Quantity:
- Payment:
- Shipping:
Inventory:4,801
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Product details
Overview
MC78M12BT from onsemi is a 500 mA, 12 V fixed-output linear voltage regulator in TO-220 package, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation for rugged local on-card regulation. It delivers stable 12 V output across −40°C to +125°C junction temperature with ±4% output voltage tolerance (11.5–12.5 V at 25°C) and supports peak output current up to 700 mA in industrial power supply applications.
For engineers reviewing the MC78M12BT datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage (2.0 V typical), ripple rejection (55 dB at 100 mA/120 Hz), load regulation (240 mV over 5–500 mA), thermal resistance (JC = 5.0°C/W), and automotive-grade AEC-Q100 qualification via NCV variants.
Technical Context
The MC78M12BT implements a monolithic three-terminal series pass regulator architecture with built-in protection circuitry: thermal overload shutdown activates at +150°C junction temperature, and internal current limiting caps output at ~350 mA under short-circuit conditions. Safe-area compensation dynamically 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 uses a PNP pass transistor with ground-referenced feedback, enabling simple integration into low-noise analog subsystems and embedded control rails where precision and reliability outweigh efficiency concerns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 12 V nominal; 11.4–12.6 V over full line/load/temperature range - ensures compatibility with 12 V logic and analog circuits requiring tight DC rail stability. |
| Max Output Current | 500 mA continuous with adequate heatsinking - supports mid-power microcontroller boards, sensor interfaces, and industrial I/O modules. |
| Dropout Voltage | 2.0 V typical at 25°C - mandates minimum 14 V input for regulated 12 V output, constraining use in low-headroom battery systems. |
| Ripple Rejection | 55 dB at 120 Hz, 100 mA load - suppresses AC line noise from unregulated supplies, critical for analog signal chains and ADC references. |
| Thermal Resistance JC | 5.0°C/W - enables direct heatsink mounting to Pin 2 (GND) for thermal management in enclosed enclosures or high-ambient environments. |
| Operating Temperature | −40°C to +125°C junction - certified for automotive under-hood and industrial control cabinet deployments. |
| Short-Circuit Limit | 350 mA typical at 35 V input - provides self-protection during fault conditions without external current-sense circuitry. |
Pinout & Package
MC78M12BT uses the TO-220 (Case 221AB) package with heatsink surface electrically connected to Pin 2 (Ground). The plastic body has standardized mechanical dimensions (A = 14.48–15.75 mm, B = 9.66–10.28 mm) and is Pb-free (RoHS compliant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Input | Unregulated DC input terminal; must be bypassed with ≥0.33 µF capacitor near device to prevent oscillation under dynamic load. |
| 2 | Ground | Reference node and thermal path; heatsink surface is internally tied to this pin - requires low-thermal-resistance mounting for >2 W dissipation. |
| 3 | Output | Regulated 12 V output; capable of sourcing up to 500 mA continuously; output capacitance not required but improves transient response. |
Key Features
| Feature | Design Value |
|---|---|
| No external components required | Enables drop-in replacement in legacy 78xx designs without adding compensation networks or feedback resistors. |
| Internal thermal shutdown | Automatically disables output above +150°C junction temperature, preventing permanent damage during sustained overload or poor heatsinking. |
| Short-circuit current limiting | Clamps output to ~350 mA during hard shorts, eliminating need for fuse or external current-limiting transistor in most applications. |
| Safe-area compensated pass transistor | Reduces short-circuit current as VI–VO increases, protecting the die during high-differential-voltage faults (e.g., 35 V input short). |
| Pb-free TO-220 package | Complies with RoHS Directive 2011/65/EU; compatible with standard through-hole reflow and wave solder processes. |
Applications
| Industrial PLC Power Rails | Automotive Body Control Modules |
|---|---|
|
Use Scenario: Providing clean 12 V supply to microcontrollers, CAN transceivers, and analog sensors inside programmable logic controllers housed in metal cabinets with ambient temperatures up to 70°C. IC Role / Device Role / Timing Role: Local point-of-load regulator converting 24 VDC system bus to stable 12 V for logic and interface ICs. Use Value: Internal thermal protection prevents latch-up during cabinet overheating; 5.0°C/W JC enables compact heatsink integration within constrained chassis space. |
Use Scenario: Powering door module ECUs in vehicles where input voltage varies from 9 V (cranking) to 16 V (load dump), with operation required down to −40°C. IC Role / Device Role / Timing Role: Primary 12 V regulator for MCU, LIN transceiver, and window motor driver ICs in non-safety-critical body electronics. Use Value: −40°C to +125°C rating matches automotive under-dash requirements; NCV78M12BDTRKG variant offers AEC-Q100 qualification for production deployment. |
| Legacy Equipment Retrofit | Test & Measurement Instrumentation |
|
Use Scenario: Replacing obsolete 78M12 regulators in aging medical analyzers and factory calibration tools where PCB layout cannot be modified. IC Role / Device Role / Timing Role: Pin-compatible upgrade delivering identical 12 V output with improved thermal robustness and Pb-free compliance. Use Value: Same TO-220 footprint and pinout as original 78M12; eliminates redesign risk while extending product lifecycle and meeting modern environmental standards. |
Use Scenario: Generating low-noise 12 V bias for op-amp front-ends, reference buffers, and ADC drivers in benchtop multimeters and oscilloscope auxiliary supplies. IC Role / Device Role / Timing Role: Low-ripple DC source for analog signal conditioning stages sensitive to power supply noise. Use Value: 55 dB ripple rejection at 120 Hz suppresses mains-borne noise; 75 µV RMS output noise (10 Hz–100 kHz) preserves signal integrity in µV-level measurements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fixed-output linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC78M12CDTRKG | Same 12 V output and TO-220 pinout, but rated for 0°C to +125°C (not −40°C); ±4% tolerance; no automotive qualification. | Suitable for commercial/industrial equipment operating above freezing; not approved for automotive under-hood use. | Select when cost sensitivity outweighs extended temperature range; verify ambient does not fall below 0°C. |
| NCV78M12BDTRKG | Identical electrical specs and −40°C to +125°C rating, but in DPAK-3 surface-mount package (Case 369C); same Pb-free marking. | Required for automated SMT assembly lines; lacks TO-220 heatsink tab - needs PCB copper pour or external heatsink for >1.5 W dissipation. | Choose for new SMT designs prioritizing board space and reflow compatibility; avoid if mechanical heatsink mounting is mandatory. |
Compared with MC78M12BT, MC78M12CDTRKG trades extended cold-temperature capability for lower cost in commercial applications, while NCV78M12BDTRKG replaces through-hole mounting with surface-mount flexibility at the expense of thermal performance without PCB-level thermal design.
Availability
MC78M12BT is available at Aetrix Electronics and suitable for industrial PLC power rails, automotive body control modules, legacy equipment retrofit, and test & measurement instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MC78M12BT 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 MC78Mxx series was designed as a rugged, drop-in replacement for legacy 78xx regulators, targeting cost-sensitive, high-reliability applications where simplicity, thermal resilience, and long-term availability outweigh switching efficiency demands.
FAQ
What is the maximum input voltage rating for the MC78M12BT?
The MC78M12BT supports a maximum input voltage of 35 Vdc under normal operating conditions, as specified in its Absolute Maximum Ratings table. Exceeding this voltage risks permanent damage, especially during transient events like load dump in automotive systems. For reliable operation, maintain input within 14.5–27 Vdc per its electrical characteristics - sufficient headroom above the 12 V output while staying well below the 35 V limit.
Does the MC78M12BT require an input bypass capacitor?
Yes, the MC78M12BT requires an input bypass capacitor - typically ≥0.33 µF tantalum or low-ESR ceramic - mounted directly across Pins 1 (Input) and 2 (Ground) with minimal lead length. This stabilizes the regulator under fast load transients and prevents oscillation when connected via long traces or high-impedance sources, as explicitly recommended in the Applications Information section of the datasheet.
Can the MC78M12BT be used in automotive applications?
The MC78M12BT itself is rated for −40°C to +125°C junction temperature and meets industrial reliability requirements, but it is not AEC-Q100 qualified. For production automotive use, onsemi offers the NCV78M12BDTRKG variant - identical in electrical performance and temperature range, with formal AEC-Q100 qualification and PPAP capability - making it the approved choice for body control modules and other non-safety-critical vehicle systems.
How does thermal management work on the MC78M12BT?
The MC78M12BT's TO-220 package features a metal tab (heatsink surface) electrically connected to Pin 2 (Ground), enabling direct attachment to an external heatsink. Its junction-to-case thermal resistance is 5.0°C/W, so with a 10°C/W heatsink and 25°C ambient, it can dissipate ~4.2 W continuously. Without heatsinking, power dissipation is limited by ambient temperature and PCB copper area, as shown in Figure 3 of the datasheet.
What is the output voltage tolerance of the MC78M12BT at room temperature?
At TJ = 25°C, the MC78M12BT exhibits an output voltage tolerance of ±4% - specifically 11.50 V to 12.50 V - per the "MC78M12B/MC78M12C/NCV78M12B" row in the Electrical Characteristics table. This tolerance widens slightly across temperature and load, reaching ±5% (11.4–12.6 V) over full operating conditions, consistent with standard 78Mxx-series specifications.
MC78M12BT 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:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220
MC78M12BT FAQ
1.How can I place an order for MC78M12BT through Aetrix?
Please submit a Request for Quotation (RFQ) for MC78M12BT 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 MC78M12BT reliable?
The price and inventory of MC78M12BT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC78M12BT is usually 5 days.
3.What payment methods are accepted for MC78M12BT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC78M12BT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC78M12BT?
MC78M12BT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC78M12BT 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 MC78M12BT?
For technical support, including MC78M12BT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC78M12BT requirements.
6.How does Aetrix verify that MC78M12BT is sourced from the original manufacturer or authorized distributors?
All MC78M12BT 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 MC78M12BT meets industry standards.
7.What is the process for return or replacement of MC78M12BT?
All MC78M12BT units undergo pre-shipment inspection (PSI). If there is an issue with MC78M12BT, 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 MC78M12BT part is unused and in its original packaging.
Return procedure for MC78M12BT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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