MC78M08ACT Linear Voltage Regulator - Equivalent & Substitute Parts

Part Overview

The MC78M08ACT is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 8V output at 500mA in a TO-220-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and component procurement. The MC78M08ACT delivers regulated 8V output from input voltages up to 35V, with integrated over-temperature and short-circuit protection suitable for through-hole mounting applications.

Substiute Parts

MC78M08ACT

onsemiIn Stock: 793MC78M08ACT Datasheet

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L7808ABV

STMicroelectronicsIn Stock: 18496L7808ABV Datasheet

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L7808ACV

STMicroelectronicsIn Stock: 5301L7808ACV Datasheet

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L7808CV

STMicroelectronicsIn Stock: 205332L7808CV Datasheet

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UA78M08CKCS

Texas InstrumentsIn Stock: 1157UA78M08CKCS Datasheet

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UA78M08CKCSE3

Texas InstrumentsIn Stock: 2093UA78M08CKCSE3 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the MC78M08ACT is determined by the following critical parameters:

• Fixed Output Voltage: 8V (all substitutes maintain this specification)
• Package Type: TO-220-3 through-hole configuration (mechanical and thermal compatibility)
• Output Current Capability: Minimum 500mA (substitutes rated at 500mA or higher)
• Maximum Input Voltage: 35V or higher (electrical compatibility)
• Protection Features: Over-temperature and short-circuit protection (functional safety requirements)

The substitute parts are grouped into two categories based on output current rating:

Category 1 - 500mA Output Current (Direct Current Rating Match)

• UA78M08CKCS (Texas Instruments)
• UA78M08CKCSE3 (Texas Instruments)

Category 2 - 1.5A Output Current (Higher Current Capability)

• L7808ABV (STMicroelectronics)
• L7808ACV (STMicroelectronics)
• L7808CV (STMicroelectronics)

All substitutes maintain the 8V fixed output, TO-220-3 package, and required protection features. Category 2 parts provide increased current headroom for applications requiring higher output current than the original 500mA specification.

Parameter Comparison

Engineering Selection Recommendations

For Direct Current Rating Substitution (500mA Applications)

The UA78M08CKCS and UA78M08CKCSE3 from Texas Instruments provide the closest electrical match to the MC78M08ACT, maintaining identical 500mA output current and 80dB PSRR performance. Both parts are ROHS3 compliant, addressing the RoHS non-compliance status of the original part. The UA78M08CKCSE3 is supplied in tube packaging, while UA78M08CKCS packaging is unspecified. Both operate across the 0°C to 125°C temperature range and include enhanced over-current protection in addition to over-temperature and short-circuit protection.

Note: Maximum input voltage for Texas Instruments parts is 25V, compared to 35V for the MC78M08ACT. Applications requiring input voltages above 25V must use STMicroelectronics substitutes.

For Higher Current Capability (1.5A Applications)

The L7808ABV, L7808ACV, and L7808CV from STMicroelectronics provide 1.5A output current capability while maintaining 8V fixed output and TO-220-3 package compatibility. All three are ROHS3 compliant and support the full 35V maximum input voltage specification. The L7808ABV supports extended operating temperature range (-40°C to 125°C). PSRR performance decreases across this series (62dB for L7808ABV/ACV, 56dB for L7808CV), with L7808CV offering the highest inventory availability (205,300 units).

Compliance Considerations

All substitute parts are ROHS3 compliant, providing regulatory advantage over the RoHS non-compliant MC78M08ACT. All parts maintain REACH unaffected status and EAR99 ECCN classification. Selection should prioritize ROHS3 compliant alternatives for new designs and long-term product support.

Frequently Asked Questions (FAQ)

Q: Can I use a 1.5A rated substitute in place of the 500mA MC78M08ACT?

A: Yes. The L7808 series (L7808ABV, L7808ACV, L7808CV) are direct substitutes with higher current capability. The 1.5A rating provides additional headroom and does not negatively impact 500mA applications. All maintain the 8V fixed output and TO-220-3 package.

Q: What is the difference between UA78M08CKCS and UA78M08CKCSE3?

A: Both parts are electrically identical with 500mA output current, 8V fixed output, and 80dB PSRR. The primary difference is packaging: UA78M08CKCSE3 is supplied in tube packaging, while UA78M08CKCS packaging is unspecified. Both are ROHS3 compliant and obsolete status.

Q: Why do some substitutes have lower maximum input voltage (25V vs 35V)?

A: Texas Instruments UA78M08 series parts are rated for 25V maximum input, while onsemi MC78M08ACT and STMicroelectronics L7808 series support 35V. For applications with input voltages between 25V and 35V, use STMicroelectronics L7808 series substitutes.

Q: Are all substitutes RoHS compliant?

A: Yes. All listed substitute parts are ROHS3 compliant, addressing the RoHS non-compliance of the original MC78M08ACT. This provides regulatory advantage for new designs and updated product certifications.

Q: What is the difference in PSRR between substitute options?

A: The MC78M08ACT and Texas Instruments UA78M08 series maintain 80dB PSRR at 120Hz. STMicroelectronics L7808 series shows reduced PSRR: L7808ABV and L7808ACV at 62dB, and L7808CV at 56dB. For noise-sensitive applications, prioritize Texas Instruments substitutes or L7808ABV/ACV.

Q: Can I use L7808CV in applications requiring -40°C operation?

A: No. L7808CV operates from 0°C to 125°C. For extended low-temperature operation to -40°C, use L7808ABV, which is rated -40°C to 125°C.

Q: Are all substitutes available in the same TO-220-3 package?

A: Yes. All substitute parts use TO-220-3 through-hole package, ensuring mechanical and thermal compatibility with the original MC78M08ACT footprint and mounting requirements.