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onsemi MC78M20CT
- Part No.:
- MC78M20CT
- Manufacturer:
- onsemi
- Package:
- TO-220-3
- Datasheet:
-
MC78M20CT.pdf
- Description:
- IC REG LINEAR 20V 500MA TO220AB
- Quantity:
- Payment:
- Shipping:
Inventory:1,707
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Product details
Overview
MC78M20CT from onsemi is a fixed-output, 500 mA positive voltage regulator in TO-220 package, delivering a nominal 20 V output with ±4% tolerance (19.2–20.8 V at 25°C), 2.0 V dropout voltage, and internal thermal shutdown and short-circuit protection. It operates across −40°C to +125°C and is used for local on-card regulation in industrial power supplies and embedded control systems requiring stable mid-voltage rails.
For engineers reviewing the MC78M20CT datasheet, pinout, applications, or equivalent options, key selection criteria include output accuracy under load variation (±1.0 V over 5–350 mA), ripple rejection (52 dB at 120 Hz), peak current capability (700 mA), and thermal resistance (JC = 5.0°C/W) - all critical for heat-limited PCB layouts and automotive-grade reliability validation.
Technical Context
The MC78M20CT implements a monolithic series pass transistor architecture with safe-area compensation, enabling robust operation under transient overload and thermal stress. Its internal current limiting activates at ~350 mA during short-circuit conditions, while thermal shutdown engages at TJ ≥ +150°C.
Designed for fixed-voltage regulation without external components, it requires only input/output bypass capacitors for stability. Input voltage range is 23–35 V DC, supporting common 24 V industrial bus inputs with sufficient headroom for line transients and ripple.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 20 V nominal (19.2–20.8 V at 25°C); ensures stable mid-rail supply for analog front-ends and logic interfaces. |
| Max Output Current | 500 mA continuous (700 mA peak); supports moderate-power sensors, op-amps, and microcontroller peripherals. |
| Dropout Voltage | 2.0 V typical at 350 mA; enables operation with 24 V input down to 22 V under full load without regulation loss. |
| Ripple Rejection | 52 dB at 120 Hz (24 V input, 100 mA load); suppresses rectified AC noise in unregulated DC supplies. |
| Thermal Resistance JC | 5.0°C/W; allows direct heatsink mounting to Pin 2 (GND) for >7 W dissipation at ambient ≤50°C. |
| Operating Temp Range | −40°C to +125°C junction; qualified for under-hood automotive and industrial control environments. |
| Short-Circuit Limit | 350 mA typical; protects upstream circuitry during sustained output faults without latch-up. |
Pinout & Package
MC78M20CT uses the TO-220 (Case 221AB) package with heatsink surface electrically connected to Pin 2 (GND). The plastic body provides isolation, and mechanical mounting via the tab ensures low thermal impedance to external heatsinks.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Input | Unregulated DC input (23–35 V); must be bypassed with ≥0.33 µF capacitor near device for high-frequency stability. |
| Pin 2 | Ground | Common reference and thermal path; heatsink surface is internally tied to this pin - mandatory for thermal management. |
| Pin 3 | Output | Regulated 20 V output; requires ≥0.1 µF ceramic capacitor for transient response and EMI suppression. |
Key Features
| Feature | Design Value |
|---|---|
| No external components required | Self-contained regulation with integrated pass transistor, bias network, and protection - reduces BOM count and layout area. |
| Internal thermal overload protection | Automatic shutdown at TJ ≥ +150°C prevents permanent damage during sustained overloads or poor heatsinking. |
| Internal short-circuit current limiting | Clamps output current to ~350 mA during fault, limiting power dissipation and avoiding catastrophic failure. |
| Safe-area compensated pass transistor | Reduces short-circuit current as VI–VO increases, preventing second breakdown during high-differential-voltage faults. |
| Pb-free TO-220 package | RoHS-compliant plastic package (Case 221AB) with G-marking; suitable for automotive and industrial reflow assembly. |
Applications
| Industrial Power Supply | Automotive Body Control Module |
|---|---|
Use Scenario: Local regulation of 24 V vehicle battery-derived rail to power MCU I/O, CAN transceivers, and sensor interfaces. IC Role / Device Role / Timing Role: Fixed 20 V linear regulator providing clean, isolated supply independent of battery voltage fluctuations. Use Value: Maintains 20 V ±1.0 V over 5–350 mA load range and −40°C to +125°C, meeting AEC-Q100 temperature requirements without external compensation. |
Use Scenario: On-board 20 V rail generation for HVAC actuators, window lift drivers, and lighting controllers in BCM designs. IC Role / Device Role / Timing Role: Primary voltage regulator supplying motor driver ICs and analog signal conditioning circuits. Use Value: Withstands 35 V load dump transients when paired with input TVS, and delivers 500 mA with <200 mV load regulation up to 200 mA. |
| Test Equipment Power Rail | Programmable Logic Controller (PLC) I/O Module |
Use Scenario: Stable 20 V supply for precision DACs, ADC references, and op-amp biasing in benchtop instrumentation. IC Role / Device Role / Timing Role: Low-noise local regulator minimizing supply-induced errors in measurement circuits. Use Value: Output noise of 110 µV RMS (10 Hz–100 kHz) and 52 dB ripple rejection ensure <0.05% measurement error contribution. |
Use Scenario: Dedicated 20 V rail for isolated digital I/O drivers and relay coil supplies in modular PLC backplanes. IC Role / Device Role / Timing Role: Point-of-load regulator decoupling field-side power from main 24 V bus. Use Value: Thermal shutdown and short-circuit protection enable fault-tolerant operation in harsh factory environments with minimal supervision. |
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 |
|---|---|---|---|
| MC78M20CDTG | DPAK-3 (Case 369C) package; lower thermal resistance to air (92°C/W vs. 70°C/W), no integral heatsink tab. | Better suited for compact SMT layouts with limited board space; requires PCB copper pour for thermal management. | Select MC78M20CDTG for automated assembly and space-constrained designs where heatsink mounting is impractical. |
| NCV78M20BDTRKG | Automotive-grade variant with −40°C to +125°C operation, AEC-Q100 qualification, and PPAP support. | Required for safety-critical automotive subsystems; includes enhanced ESD robustness (2 kV HBM) and lot traceability. | Choose NCV78M20BDTRKG when compliance with automotive quality and lifecycle requirements is mandatory. |
Compared with MC78M20CT, the DPAK alternative offers surface-mount flexibility but reduced thermal performance, while the NCV variant adds automotive qualification at the cost of higher unit price and longer lead times - both require PCB redesign and cannot be drop-in replacements.
Availability
MC78M20CT is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, and test equipment requiring stable component supply with consistent parametric performance and long-term manufacturability.
Supply support for MC78M20CT 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 solutions for automotive, industrial, and cloud infrastructure markets.
The MC78Mxx series was designed as a rugged, drop-in replacement for legacy 78xx regulators - optimized for local on-card regulation with enhanced thermal protection and extended temperature operation.
FAQ
What is the maximum input voltage rating for MC78M20CT?
The MC78M20CT has an absolute maximum input voltage of 40 V DC, as specified in the Maximum Ratings table. However, for reliable operation within specifications, the recommended input range is 23–35 V DC - ensuring adequate headroom above the 20 V output while maintaining acceptable power dissipation and thermal margin.
Does MC78M20CT require external capacitors for stable operation?
Yes, MC78M20CT requires an input bypass capacitor (≥0.33 µF tantalum or low-ESR ceramic) placed directly across Pins 1 and 2, and an output capacitor (≥0.1 µF ceramic) across Pins 2 and 3. These capacitors prevent oscillation under dynamic load changes and suppress high-frequency noise, as confirmed by onsemi's application guidelines.
Can MC78M20CT be used in automotive applications?
The standard MC78M20CT is rated for −40°C to +125°C operation and meets industrial reliability standards, but it is not AEC-Q100 qualified. For automotive use, the NCV78M20BDTRKG variant - explicitly qualified to AEC-Q100 Grade 1 and PPAP-capable - should be selected instead of MC78M20CT.
What is the thermal resistance from junction to case (θJC) for MC78M20CT?
The MC78M20CT has a junction-to-case thermal resistance (θJC) of 5.0°C/W, measured from the silicon die to the metal tab (Pin 2). This value assumes proper mechanical contact between the TO-220 tab and an external heatsink, and is critical for calculating maximum allowable power dissipation at a given ambient temperature.
How does MC78M20CT behave during output short-circuit conditions?
Under output short-circuit, MC78M20CT limits current to approximately 350 mA (typical) and activates thermal shutdown if junction temperature exceeds +150°C. This dual-protection scheme prevents device destruction and allows automatic recovery once the fault is removed and temperature falls below the hysteresis threshold.
MC78M20CT 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):
- 40V
- Voltage - Output (Min/Fixed):
- 20V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- -
- Current - Output:
- 500mA
- Current - Quiescent (Iq):
- -
- Current - Supply (Max):
- -
- PSRR:
- 70dB (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
MC78M20CT FAQ
1.How can I place an order for MC78M20CT through Aetrix?
Please submit a Request for Quotation (RFQ) for MC78M20CT 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 MC78M20CT reliable?
The price and inventory of MC78M20CT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC78M20CT is usually 5 days.
3.What payment methods are accepted for MC78M20CT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC78M20CT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC78M20CT?
MC78M20CT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC78M20CT 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 MC78M20CT?
For technical support, including MC78M20CT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC78M20CT requirements.
6.How does Aetrix verify that MC78M20CT is sourced from the original manufacturer or authorized distributors?
All MC78M20CT 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 MC78M20CT meets industry standards.
7.What is the process for return or replacement of MC78M20CT?
All MC78M20CT units undergo pre-shipment inspection (PSI). If there is an issue with MC78M20CT, 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 MC78M20CT part is unused and in its original packaging.
Return procedure for MC78M20CT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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