LM78M08CT Equivalent & Substitute Parts

Part Overview

The LM78M08CT is a linear voltage regulator IC from 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 production continuity. The LM78M08CT serves applications requiring stable 8V regulation with thermal and short-circuit protection in through-hole mounting configurations.

Substiute Parts

LM78M08CT

onsemiIn Stock: 1000LM78M08CT Datasheet

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L7808ABV

STMicroelectronicsIn Stock: 18496L7808ABV Datasheet

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L7808ACV

STMicroelectronicsIn Stock: 5301L7808ACV Datasheet

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L7808ACV-DG

STMicroelectronicsIn Stock: 1639L7808ACV-DG Datasheet

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L7808CV

STMicroelectronicsIn Stock: 205332L7808CV Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the LM78M08CT is determined by the following critical parameters:

• Output Voltage: Must be fixed at 8V
• Package / Case: Must be TO-220-3 (through-hole compatible)
• Output Configuration: Must be positive fixed output
• Protection Features: Must include over-temperature and short-circuit protection
• Input Voltage Rating: Must support maximum 35V input
• Mounting Type: Must be through-hole

The substitute parts listed below meet these core requirements. Output current capability may exceed the original specification (1.5A vs. 500mA), which is acceptable as higher current ratings provide design margin without affecting voltage regulation performance. Variations in quiescent current, PSRR, and operating temperature ranges are secondary parameters that do not prevent functional substitution when the primary criteria are met.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: L7808ACV-DG

The L7808ACV-DG from STMicroelectronics is the preferred substitute for the LM78M08CT. This part is currently in active product status, ensuring long-term availability and supply chain stability. It meets all critical electrical parameters, maintains TO-220-3 package compatibility, and carries ROHS3 compliance certification. With 1590 units in stock, this part provides immediate procurement availability.

Secondary Recommendations: L7808ABV, L7808ACV, L7808CV

All four STMicroelectronics L7808 variants are functionally equivalent to the LM78M08CT for applications requiring 8V fixed output regulation. These parts share identical output voltage, input voltage rating, package configuration, and protection features. The primary distinction is product status: L7808ACV-DG remains active, while L7808ABV, L7808ACV, and L7808CV are obsolete. For new designs or long-term production, L7808ACV-DG is preferred. For legacy system maintenance where existing inventory exists, any of these variants may be selected based on availability and cost considerations.

All substitute parts exceed the original 500mA output current specification at 1.5A, providing design margin without performance degradation. PSRR values in the substitute parts are lower than the original (56–62dB vs. 80dB), which is acceptable for standard voltage regulation applications where ripple rejection is not a critical design constraint.

Frequently Asked Questions (FAQ)

Q: Can I use L7808ACV-DG as a direct replacement for LM78M08CT?

A: Yes. The L7808ACV-DG provides identical 8V fixed output voltage, supports the same 35V maximum input voltage, uses the same TO-220-3 package, and includes equivalent over-temperature and short-circuit protection. The higher 1.5A output current rating does not affect compatibility and provides additional design margin.

Q: What is the difference between L7808ABV, L7808ACV, and L7808ACV-DG?

A: All three parts are STMicroelectronics L7808 variants with identical electrical specifications for 8V output regulation. The primary differences are product status (L7808ACV-DG is active; the others are obsolete) and operating temperature range (L7808ABV supports -40°C to 125°C; L7808ACV and L7808ACV-DG support 0°C to 125°C). For new designs, L7808ACV-DG is recommended due to active status.

Q: Why do the substitute parts have higher output current (1.5A) than the original (500mA)?

A: Higher current ratings indicate improved thermal design and manufacturing capability in the substitute parts. This does not affect voltage regulation performance and provides additional design margin for applications that may require higher transient currents or future design modifications.

Q: Are all substitute parts RoHS compliant?

A: Yes. All listed STMicroelectronics L7808 variants carry ROHS3 compliance certification, meeting environmental and material restriction requirements for modern electronics manufacturing.

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

A: Only the L7808ABV supports the extended -40°C to 125°C operating temperature range. The L7808ACV, L7808ACV-DG, and L7808CV are rated for 0°C to 125°C operation. Select L7808ABV if your application requires sub-zero temperature operation.

Q: What is the difference in PSRR between the original and substitute parts?

A: The LM78M08CT has 80dB PSRR at 120Hz, while the L7808 variants range from 56dB to 62dB. PSRR (Power Supply Rejection Ratio) measures ripple attenuation. The lower PSRR in substitutes is acceptable for standard voltage regulation applications where input ripple is within normal operating ranges.