LM7818ACT Linear Voltage Regulator 18V 1A Equivalent & Substitute Parts

Part Overview

The LM7818ACT is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 18V output at 1A current capacity 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 regulator includes over-temperature and short-circuit protection features suitable for power management applications requiring stable 18V rails.

Substiute Parts

LM7818ACT

onsemiIn Stock: 1226LM7818ACT Datasheet

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MC7818BTG

onsemiIn Stock: 17164MC7818BTG Datasheet

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MC78M18CTG

onsemiIn Stock: 3179MC78M18CTG Datasheet

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MC7818CTG

onsemiIn Stock: 1503MC7818CTG Datasheet

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L7818CV-DG

STMicroelectronicsIn Stock: 65494L7818CV-DG Datasheet

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L78S18CV

STMicroelectronicsIn Stock: 2795L78S18CV Datasheet

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MC78M18BTG

onsemiIn Stock: 5829MC78M18BTG Datasheet

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MC7818ACTG

onsemiIn Stock: 1773MC7818ACTG Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the LM7818ACT are classified based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

• Fixed output voltage of 18V
• TO-220-3 through-hole package
• Positive output configuration
• Over-temperature and short-circuit protection
• Maximum input voltage of 35V

Substitutes are grouped into two categories:

Parametric Equivalents maintain identical or superior electrical specifications including output current (1A), voltage dropout (2V @ 1A typical), and quiescent current performance. These parts are direct functional replacements.

Similar Substitutes provide the same 18V fixed output and TO-220-3 package but with variations in output current capacity (500mA or 2A), quiescent current, or PSRR performance. These parts are suitable when the application can accommodate the specified parameter differences.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: MC7818CTG

MC7818CTG is the preferred substitute for the LM7818ACT. Both parts maintain identical electrical specifications (1A output current, 2V dropout voltage typical, 0°C to 125°C operating range), identical TO-220-3 package, and equivalent protection features. MC7818CTG holds active product status and carries ROHS3 compliance certification, providing long-term availability and regulatory alignment. Quiescent current is improved at 6.5 mA versus 8 mA in the original part.

Secondary Recommendation: MC7818BTG

MC7818BTG provides identical electrical performance to the LM7818ACT with extended operating temperature range (-40°C to 125°C). This part is active and ROHS3 compliant. Selection is appropriate when the application requires cold-temperature operation beyond 0°C.

Alternative for Higher Current Applications: L7818CV-DG or L78S18CV

When the application requires output current exceeding 1A, L7818CV-DG (1.5A) or L78S18CV (2A) provide higher current capacity while maintaining 18V fixed output and TO-220-3 package compatibility. L78S18CV additionally supports extended operating temperature to 150°C and includes over-current protection. Both parts are obsolete but available in inventory.

Not Recommended: MC78M18CTG and MC78M18BTG

These 500mA variants are not suitable as direct substitutes for the LM7818ACT due to reduced output current capacity (500mA versus 1A). Selection is appropriate only when the application current requirement does not exceed 500mA.

Frequently Asked Questions (FAQ)

Q: Can MC7818CTG directly replace LM7818ACT without circuit modification?

A: Yes. MC7818CTG maintains identical electrical specifications, package type (TO-220-3), and pin configuration. No circuit modifications are required. The part is a direct functional replacement.

Q: What is the difference between MC7818BTG and MC7818CTG?

A: Both parts provide 1A output at 18V with identical dropout voltage and protection features. MC7818BTG operates from -40°C to 125°C, while MC7818CTG operates from 0°C to 125°C. MC7818CTG has lower quiescent current (6.5 mA versus 8 mA). Selection depends on minimum operating temperature requirements.

Q: Why is the LM7818ACT obsolete, and what does this mean for my design?

A: Obsolete status indicates the manufacturer has discontinued production. Existing inventory remains available, but long-term supply cannot be guaranteed. Transitioning to active alternatives such as MC7818CTG ensures design continuity and future production support.

Q: Can I use L78S18CV (2A) in place of LM7818ACT (1A)?

A: Yes, from an electrical compatibility perspective. L78S18CV maintains 18V fixed output, TO-220-3 package, and identical protection features. The higher current rating (2A) does not create compatibility issues in circuits designed for 1A. However, verify that your PCB thermal design accommodates the potentially higher power dissipation if the application draws near the 2A limit.

Q: Are all substitute parts ROHS3 compliant?

A: Most active and recently obsolete substitutes carry ROHS3 compliance. The original LM7818ACT does not specify RoHS status. If RoHS compliance is a design requirement, confirm certification status with the selected substitute part before procurement.

Q: What is the significance of PSRR (Power Supply Rejection Ratio) differences between parts?

A: PSRR measures the regulator's ability to reject input voltage ripple. The LM7818ACT specifies 69dB at 120Hz, while most onsemi substitutes specify 57dB. Higher PSRR provides better noise rejection. If your application is sensitive to supply ripple, the LM7818ACT's higher PSRR may be preferable, but 57dB is adequate for most industrial and consumer applications.

Q: Can I substitute MC78M18CTG (500mA) if my circuit only draws 400mA?

A: Yes. The 500mA rating is the maximum output current. If your application draws 400mA, MC78M18CTG will operate within specification. However, verify that the regulator's thermal performance remains acceptable under your specific operating conditions and ambient temperature.