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onsemi MC79M12CT
- Part No.:
- MC79M12CT
- Manufacturer:
- onsemi
- Package:
- TO-220-3
- Datasheet:
-
MC79M12CT.pdf
- Description:
- IC REG LINEAR -12V 500MA TO220AB
- Quantity:
- Payment:
- Shipping:
Inventory:1,726
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Product details
Overview
MC79M12CT from onsemi is a fixed-output, three-terminal negative voltage regulator delivering −12 V at up to 500 mA, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It operates across −40 °C to +125 °C (B-grade), uses TO-220-3 packaging, and requires no external components for basic regulation - commonly deployed in industrial power supplies and analog signal conditioning circuits.
For engineers reviewing the MC79M12CT datasheet, pinout, applications, or equivalent options, key selection considerations include its −12 V output tolerance (±4.0%), dropout voltage (1.1 V), ripple rejection (60 dB at 120 Hz), thermal resistance (θJA = 65 °C/W), and compatibility with standard TO-220 heatsinking layouts.
Technical Context
The MC79M12CT implements a monolithic bipolar linear regulator architecture with built-in protection circuitry: current limiting prevents damage during overload, thermal shutdown activates above +150 °C junction temperature, and safe-area compensation ensures transistor reliability under high-voltage/high-current transients. Its input voltage range extends to −35 V, supporting operation with ≥1.1 V headroom over output.
Designed for stable DC biasing in dual-rail systems, it maintains output regulation across 5 mA–500 mA load currents and exhibits 30 mV typical load regulation. The device's −12 V nominal output is specified at TJ = 25 °C with ±0.5 V variation over full operating temperature and line conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | −12 V nominal, −11.4 V to −12.6 V over full line/load/temperature range - ensures stable negative rail for op-amps and ADCs. |
| Maximum Output Current | 500 mA continuous - sufficient for powering multiple low-power analog stages without external pass devices. |
| Input Voltage Range | −35 V to −14.5 V - supports wide-input industrial supplies while maintaining regulation down to 1.1 V dropout. |
| Ripple Rejection | 60 dB at 120 Hz - suppresses rectified AC noise in unregulated DC inputs before downstream analog circuitry. |
| Thermal Resistance (Junction-to-Ambient) | 65 °C/W (TO-220, free-air) - dictates minimum heatsink requirement for sustained 500 mA operation at +50 °C ambient. |
| Dropout Voltage | 1.1 V at 500 mA - defines minimum input-to-output differential needed to sustain regulation under full load. |
| Operating Junction Temperature | −40 °C to +150 °C - enables deployment in automotive engine compartments and industrial enclosures without derating. |
Pinout & Package
MC79M12CT uses the TO-220-3 (Case 221AB) package: a through-hole, single-gauge thermally enhanced outline with metal tab electrically connected to Pin 2 (Input). The package features standardized mounting hole and lead spacing for mechanical compatibility with common heatsinks and PCB footprints.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Ground | Reference node for output voltage; must be tied to system common ground - not floating or isolated. |
| Pin 2 | Input | Negative input terminal; accepts unregulated −14.5 V to −35 V supply; metal tab is electrically connected here. |
| Pin 3 | Output | Regulated −12 V source; requires 1.0 µF output capacitor for stability and transient response per datasheet. |
Key Features
| Feature | Design Value |
|---|---|
| No external components required | Enables compact, low-BOM designs - only input/output capacitors needed for basic operation. |
| Internal thermal overload protection | Automatically disables output above +150 °C junction temperature, preventing permanent failure during fault conditions. |
| Internal short-circuit current limiting | Clamps output current to safe levels during output shorts, eliminating need for external fusing in most applications. |
| Safe-area compensated output transistor | Guarantees SOA compliance across voltage/current combinations - avoids second breakdown in dynamic loads. |
| Pb-free TO-220 package option | MC79M12CTG variant available for RoHS-compliant assembly without performance trade-offs. |
Applications
| Industrial Power Supply | Analog Signal Conditioning |
|---|---|
|
Use Scenario: Providing stable −12 V rail in programmable logic controller (PLC) I/O modules with shared ground between analog and digital sections. IC Role / Device Role / Timing Role: Negative voltage regulator supplying bias to op-amps, instrumentation amplifiers, and DAC reference circuits. Use Value: Maintains ≤240 mV load regulation across 5–500 mA, ensuring consistent gain and offset performance despite varying sensor channel count. |
Use Scenario: Dual-rail power for audio preamplifier stages in broadcast equipment requiring low-noise, low-drift operation. IC Role / Device Role / Timing Role: Fixed negative supply generator referenced to system ground, paired with MC78M12CT for symmetric ±12 V rails. Use Value: Delivers 75 µV RMS output noise (10 Hz–100 kHz), minimizing audible hiss and preserving SNR in high-fidelity signal paths. |
| Test & Measurement Equipment | Legacy Industrial Control |
|
Use Scenario: Biasing precision ADC front-ends in portable multimeters where battery-derived input voltage varies widely. IC Role / Device Role / Timing Role: Regulated negative reference source for ADC driver stages and reference buffers. Use Value: Achieves 60 dB ripple rejection at 120 Hz, suppressing switching artifacts from onboard DC-DC converters feeding the analog section. |
Use Scenario: Retrofit replacement for aging −12 V regulators in factory automation panels with legacy 24 V DC bus infrastructure. IC Role / Device Role / Timing Role: Drop-in compatible negative regulator supporting long-lifecycle maintenance of discontinued control hardware. Use Value: Matches original TO-220 footprint and electrical specs (±4.0% tolerance, 500 mA rating), enabling direct PCB-level substitution without redesign. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative fixed-voltage regulation applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM337T | −1.25 V to −37 V adjustable output; requires two external resistors; higher dropout (1.5 V); 1.5 A max current. | Used where output voltage flexibility or higher current is needed; less suitable for space-constrained fixed-rail designs. | Select LM337T only when adjustable output or >500 mA capability is required - adds BOM cost and layout complexity. |
| MC7912CT | Same −12 V output, TO-220 package, but obsolete part number (discontinued per onsemi docs); identical electrical specs and pinout. | No functional difference - used historically in legacy designs; MC79M12CT replaces it with updated manufacturing and Pb-free options. | Prefer MC79M12CT for new designs due to active status, guaranteed supply, and RoHS compliance; MC7912CT is not recommended for production. |
Compared with LM337T and MC7912CT, the MC79M12CT offers optimal balance of simplicity (no external resistors), proven ruggedness (safe-area compensation), and lifecycle support - making it the preferred choice for fixed −12 V applications where reliability and long-term availability are critical.
Availability
MC79M12CT is available at Aetrix Electronics and suitable for industrial power supplies, analog signal conditioning, test & measurement equipment, and legacy control system upgrades requiring stable component supply and long-term sourcing assurance.
Supply support for MC79M12CT 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, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.
The MC79M00 series was designed specifically to provide robust, drop-in negative complements to the MC78M00 positive regulators - targeting cost-sensitive, high-reliability industrial and embedded power applications.
FAQ
What is the maximum input voltage rating for MC79M12CT?
The MC79M12CT has a maximum input voltage rating of −35 V DC, as specified in the Absolute Maximum Ratings table. Operation beyond this voltage risks permanent damage. For reliable regulation, the input must remain at least 1.1 V more negative than the −12 V output - i.e., ≤ −13.1 V under full load - even at the peak of input ripple.
Does MC79M12CT require external capacitors, and if so, what values are recommended?
Yes, MC79M12CT requires an input capacitor (0.33 µF) if located remotely from the main filter, and a 1.0 µF output capacitor for stability and improved transient response. These values are specified in the Standard Application schematic on page 1 of the datasheet and are critical to prevent oscillation under dynamic load conditions.
Is MC79M12CT pin-compatible with older MC7912CT regulators?
Yes, MC79M12CT is pin-compatible and functionally identical to the discontinued MC7912CT - same TO-220-3 package, identical pinout (Pin 1: Ground, Pin 2: Input, Pin 3: Output), and matching electrical specifications including −12 V output, 500 mA rating, and thermal protection features.
What is the thermal resistance and heatsinking requirement for MC79M12CT at 500 mA?
MC79M12CT has θJA = 65 °C/W in free-air TO-220 configuration. At 500 mA with 1.1 V dropout (0.55 W dissipation), junction temperature rise is ~36 °C above ambient. To stay within the +150 °C max junction limit at +50 °C ambient, a heatsink reducing θJA to ≤40 °C/W is recommended for continuous full-load operation.
What protection features does MC79M12CT include, and how do they operate?
MC79M12CT integrates three protection functions: (1) internal short-circuit current limiting caps output current to prevent damage during faults; (2) thermal shutdown disables output above +150 °C junction temperature; and (3) safe-area compensation protects the output transistor from second breakdown during high-voltage/high-current transients - all implemented without external components.
MC79M12CT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-220-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Configuration:
- Negative
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- -35V
- Voltage - Output (Min/Fixed):
- -12V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- 1.1V @ 500mA (Typ)
- Current - Output:
- 500mA
- Current - Quiescent (Iq):
- -
- Current - Supply (Max):
- -
- PSRR:
- 60dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220
MC79M12CT FAQ
1.How can I place an order for MC79M12CT through Aetrix?
Please submit a Request for Quotation (RFQ) for MC79M12CT 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 MC79M12CT reliable?
The price and inventory of MC79M12CT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC79M12CT is usually 5 days.
3.What payment methods are accepted for MC79M12CT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC79M12CT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC79M12CT?
MC79M12CT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC79M12CT 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 MC79M12CT?
For technical support, including MC79M12CT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC79M12CT requirements.
6.How does Aetrix verify that MC79M12CT is sourced from the original manufacturer or authorized distributors?
All MC79M12CT 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 MC79M12CT meets industry standards.
7.What is the process for return or replacement of MC79M12CT?
All MC79M12CT units undergo pre-shipment inspection (PSI). If there is an issue with MC79M12CT, 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 MC79M12CT part is unused and in its original packaging.
Return procedure for MC79M12CT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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