LM7818CT Linear Voltage Regulator - Equivalent & Substitute Parts

Part Overview

The LM7818CT is a linear voltage regulator IC manufactured by onsemi, delivering a fixed positive 18V output at 1A in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The LM7818CT provides over-temperature and short-circuit protection, suitable for applications requiring regulated 18V power delivery with moderate current demands.

Substiute Parts

LM7818CT

onsemiIn Stock: 2076LM7818CT Datasheet

Current PartRFQ

MC7818CTG

onsemiIn Stock: 1503MC7818CTG Datasheet

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MC78M18CTG

onsemiIn Stock: 3179MC78M18CTG Datasheet

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MC7818BTG

onsemiIn Stock: 17164MC7818BTG Datasheet

Parametric EquivalentRFQ

L78S18CV

STMicroelectronicsIn Stock: 2795L78S18CV Datasheet

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MC7818ACTG

onsemiIn Stock: 1773MC7818ACTG Datasheet

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MC78M18BTG

onsemiIn Stock: 5829MC78M18BTG Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the LM7818CT is determined by the following critical parameters:

• Output Voltage: Must be fixed at 18V
• Output Current Capability: Minimum 1A required for direct replacement
• Input Voltage Rating: Maximum 35V or higher
• Package Type: TO-220-3 through-hole configuration
• Protection Features: Over-temperature and short-circuit protection required
• Operating Temperature Range: Must support -40°C ~ 125°C or equivalent

Substitute parts are grouped into two categories:

Direct Equivalents (1A Output): Parts meeting all electrical and thermal specifications with 1A output capability, suitable for direct pin-compatible replacement.

Parametric Equivalents (Higher Current): Parts with 2A output capability that exceed the 1A requirement, providing design flexibility for applications with potential current growth or margin requirements.

Reduced Current Alternatives (500mA Output): Parts with 500mA output, suitable only for applications where current demand does not exceed 500mA.

Parameter Comparison

Engineering Selection Recommendations

Preferred Direct Replacement: MC7818BTG is the optimal substitute for the LM7818CT. Both parts are manufactured by onsemi, share identical electrical specifications (18V output, 1A current, 2V dropout voltage, 8 mA quiescent current), support the full -40°C ~ 125°C operating temperature range, and are housed in TO-220-3 packages. MC7818BTG carries Active product status and RoHS3 compliance, ensuring long-term availability and regulatory alignment.

Alternative Direct Replacement: MC7818CTG provides equivalent functionality with Active product status and RoHS3 compliance. This part operates over 0°C ~ 125°C, which is suitable for applications not requiring the full -40°C lower temperature limit. Quiescent current is slightly lower at 6.5 mA.

Higher Current Option: L78S18CV from STMicroelectronics delivers 2A output capability, exceeding the 1A requirement. This part is suitable for designs requiring additional current margin or future scalability. Operating temperature extends to 150°C. Note that this part is obsolete and carries lower PSRR (43dB) compared to the main part.

Reduced Current Alternatives: MC78M18CTG and MC78M18BTG are 500mA variants. These parts are suitable only for applications where load current does not exceed 500mA. Both are obsolete; MC78M18BTG supports the full -40°C ~ 125°C temperature range.

Frequently Asked Questions (FAQ)

Q: Can MC7818CTG directly replace LM7818CT?

A: Yes. Both parts deliver 18V at 1A with identical dropout voltage specifications and TO-220-3 packaging. MC7818CTG is Active and RoHS3 compliant. The operating temperature range is 0°C ~ 125°C versus -40°C ~ 125°C for the original; verify your application's minimum operating temperature requirement.

Q: Is MC7818BTG a suitable substitute?

A: Yes. MC7818BTG is the closest match to LM7818CT, with identical electrical performance and the same -40°C ~ 125°C operating range. It is Active and RoHS3 compliant, making it the preferred long-term replacement.

Q: Can I use L78S18CV as a replacement?

A: L78S18CV is pin-compatible and delivers the required 18V output. However, it provides 2A output versus the 1A requirement, and PSRR is lower at 43dB. This part is obsolete. Use only if your application benefits from the higher current capability.

Q: What is the difference between MC7818 and MC78M18 variants?

A: The MC7818 series delivers 1A output, while MC78M18 delivers 500mA. The "M" designation indicates the reduced current rating. Select MC7818 variants for 1A applications and MC78M18 only if your load current does not exceed 500mA.

Q: Are all substitute parts RoHS compliant?

A: MC7818BTG and MC7818CTG are RoHS3 compliant. L78S18CV, MC78M18CTG, and MC78M18BTG are RoHS3 compliant. The original LM7818CT does not specify RoHS status. Verify compliance requirements for your application.

Q: What is the significance of the operating temperature range difference?

A: LM7818CT and MC7818BTG support -40°C ~ 125°C. MC7818CTG and MC7818ACTG support 0°C ~ 125°C. If your application operates below 0°C, select MC7818BTG or MC78M18BTG. For standard industrial applications (0°C and above), MC7818CTG is acceptable.

Q: Can I substitute a 500mA part in a 1A application?

A: No. MC78M18CTG and MC78M18BTG are rated for 500mA maximum output. Using these in a 1A application will cause the regulator to exceed its current rating, resulting in thermal shutdown or device failure. Use only in applications confirmed to draw 500mA or less.