MC7818AECT Equivalent & Substitute Parts

Part Overview

The MC7818AECT is a linear voltage regulator IC from 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 MC7818AECT delivers regulated 18V output from input voltages up to 35V with integrated over-temperature and short-circuit protection.

Key Parameters

Parameter	Value
Manufacturer Part Number	MC7818AECT
Manufacturer	onsemi
Category	Power Management (PMIC)
Output Voltage (Fixed)	18V
Output Current	1A
Input Voltage (Max)	35V
Voltage Dropout (Max)	2V @ 1A (Typ)
Quiescent Current	6 mA
PSRR	57dB (120Hz)
Protection Features	Over Temperature, Short Circuit
Operating Temperature Range	0°C ~ 125°C
Package / Case	TO-220-3
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the MC7818AECT are grouped based on the following critical parameters that determine functional compatibility:

Primary Substitution Criteria:

Output voltage: 18V fixed
Output configuration: Positive
Package type: TO-220-3 through-hole
Mounting type: Through hole
Protection features: Over temperature and short circuit protection

Secondary Compatibility Factors:

Output current capacity (1A nominal, with higher-capacity variants acceptable for drop-in replacement)
Input voltage rating (35V maximum)
Voltage dropout characteristics
Operating temperature range (0°C ~ 125°C minimum)

Substitute parts are classified into two categories: parametric equivalents (matching all critical specifications) and similar variants (higher current capacity or extended temperature range, suitable for direct replacement in most applications).

Parameter Comparison

Part Number	Manufacturer	Output Current	Input Voltage (Max)	Voltage Dropout (Max)	Quiescent Current	PSRR	Operating Temperature	Product Status	Package
MC7818AECT	onsemi	1A	35V	2V @ 1A (Typ)	6 mA	57dB (120Hz)	0°C ~ 125°C	Obsolete	TO-220-3
MC7818CTG	onsemi	1A	35V	2V @ 1A (Typ)	6.5 mA	57dB (120Hz)	0°C ~ 125°C	Active	TO-220-3
MC7818BTG	onsemi	1A	35V	2V @ 1A (Typ)	8 mA	57dB (120Hz)	-40°C ~ 125°C	Active	TO-220-3
MC7818ACTG	onsemi	1A	35V	2V @ 1A (Typ)	6 mA	57dB (120Hz)	0°C ~ 125°C	Obsolete	TO-220-3
MC78M18CTG	onsemi	500mA	35V	—	—	70dB (120Hz)	0°C ~ 125°C	Obsolete	TO-220-3
MC78M18BTG	onsemi	500mA	35V	—	—	70dB (120Hz)	-40°C ~ 125°C	Obsolete	TO-220-3
L7818CV-DG	STMicroelectronics	1.5A	35V	2V @ 1A (Typ)	8 mA	53dB (120Hz)	0°C ~ 125°C	Obsolete	TO-220-3
L78S18CV	STMicroelectronics	2A	35V	—	8 mA	43dB (120Hz)	0°C ~ 150°C	Obsolete	TO-220-3

Engineering Selection Recommendations

Preferred Active Substitute: MC7818CTG (onsemi) is the primary recommended substitute. It is currently in active production status, maintains identical electrical specifications to the MC7818AECT, and provides RoHS3 compliance. The quiescent current difference of 0.5 mA is negligible for most applications.

Extended Temperature Range Alternative: MC7818BTG (onsemi) is suitable when operating temperature range must extend to -40°C. This part is active and RoHS3 compliant, with quiescent current of 8 mA and identical output current and voltage specifications.

Higher Current Capacity Options: L7818CV-DG (STMicroelectronics, 1.5A) and L78S18CV (STMicroelectronics, 2A) provide increased output current capacity while maintaining 18V fixed output and TO-220-3 packaging. These are suitable for applications requiring higher current delivery. L78S18CV additionally supports extended operating temperature to 150°C.

Reduced Current Variants: MC78M18CTG and MC78M18BTG provide 500mA output current. These are suitable only for applications with reduced current requirements and should not be used as direct replacements for 1A-rated designs.

Frequently Asked Questions (FAQ)

Q: Can MC7818CTG directly replace MC7818AECT? A: Yes. MC7818CTG is a parametric equivalent with identical output voltage (18V), output current (1A), input voltage rating (35V), and package (TO-220-3). The primary difference is product status: MC7818CTG is active while MC7818AECT is obsolete. Quiescent current differs by 0.5 mA, which is not significant for most applications.

Q: What is the difference between MC7818BTG and MC7818CTG? A: Both are 1A, 18V regulators in TO-220-3 packages from onsemi. MC7818BTG extends the operating temperature range to -40°C (versus 0°C for MC7818CTG) and has slightly higher quiescent current (8 mA versus 6.5 mA). Select MC7818BTG only if low-temperature operation below 0°C is required.

Q: Can I use L78S18CV (2A) instead of MC7818AECT (1A)? A: Yes, for most applications. L78S18CV provides higher current capacity (2A versus 1A) and extended temperature range (0°C ~ 150°C), making it suitable as a drop-in replacement. However, it is manufactured by STMicroelectronics rather than onsemi. Verify supply chain availability and any design-specific manufacturer preferences before substitution.

Q: Why should I avoid MC78M18CTG and MC78M18BTG? A: These parts provide only 500mA output current, which is insufficient for applications designed for 1A. Use these only if your circuit requires reduced current capacity. They are not suitable as direct replacements for the MC7818AECT.

Q: Are all substitute parts RoHS3 compliant? A: MC7818CTG and MC7818BTG are explicitly RoHS3 compliant. STMicroelectronics parts (L7818CV-DG and L78S18CV) are also RoHS3 compliant. All parts are REACH unaffected and classified as EAR99 for export control purposes.

Q: What is the significance of the TO-220-3 package? A: TO-220-3 is a through-hole package with three leads (input, ground, output). All listed substitutes use this identical package, ensuring mechanical and electrical compatibility with existing PCB layouts without modification.

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