KA78T15 Linear Voltage Regulator - Equivalent & Substitute Parts

Part Overview

The KA78T15 is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 15V output at 3A maximum current in a TO-220-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The KA78T15 serves applications requiring stable 15V regulation with moderate to high current delivery in through-hole mounting configurations.

Key Parameters

Parameter	Value
Manufacturer Part Number	KA78T15
Manufacturer	onsemi
Output Voltage (Fixed)	15V
Maximum Output Current	3A
Maximum Input Voltage	40V
Voltage Dropout (Max)	2.5V @ 3A
Package / Case	TO-220-3
Mounting Type	Through Hole
Operating Temperature Range	0°C ~ 125°C
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the KA78T15 is determined by the following critical parameters:

Output Voltage: Must be fixed at 15V
Output Configuration: Must be positive
Package Type: TO-220-3 or compatible TO-220 variants
Mounting Type: Through hole
Output Current Capability: Minimum 1A; 3A preferred for direct replacement
Maximum Input Voltage: Minimum 35V acceptable
Protection Features: Over temperature and short circuit protection required
Operating Temperature Range: 0°C minimum to 125°C maximum

Substitute parts are grouped into two categories based on current output capability:

Category A - Full Current Replacement (3A Output): No active parts in the substitute list meet the full 3A specification of the KA78T15.

Category B - Reduced Current Substitutes (1A to 1.5A Output): Multiple onsemi and third-party alternatives provide 1A to 1.5A output, suitable for applications where the full 3A capacity is not required.

Category C - Reduced Current Substitutes (500mA Output): Lower-current alternatives available for minimal power delivery requirements.

Parameter Comparison

Part Number	Manufacturer	Output Current	Max Input Voltage	Output Voltage	Dropout Voltage	Operating Temp Range	Product Status	Package
KA78T15	onsemi	3A	40V	15V	2.5V @ 3A	0°C ~ 125°C	Obsolete	TO-220-3
MC7815ABTG	onsemi	1A	35V	15V	2V @ 1A	-40°C ~ 125°C	Active	TO-220-3
MC7815ACTG	onsemi	1A	35V	15V	2V @ 1A	0°C ~ 125°C	Active	TO-220-3
MC7815BTG	onsemi	1A	35V	15V	2V @ 1A	-40°C ~ 125°C	Active	TO-220-3
MC7815CTG	onsemi	1A	35V	15V	2V @ 1A	0°C ~ 125°C	Active	TO-220-3
MC78M15ABTG	onsemi	500mA	35V	15V	Not specified	-40°C ~ 125°C	Obsolete	TO-220-3
MC78M15CTG	onsemi	500mA	35V	15V	Not specified	0°C ~ 125°C	Active	TO-220-3
NCV7815BTG	onsemi	1A	35V	15V	2V @ 1A	-40°C ~ 125°C	Obsolete	TO-220-3
AS7815AT-E1	Diodes Incorporated	1A	32V	15V	2V @ 1A	-40°C ~ 125°C	Active	TO-220-3
L7815ABV	STMicroelectronics	1.5A	35V	15V	2V @ 1A	-40°C ~ 125°C	Active	TO-220-3
L7815ACV	STMicroelectronics	1.5A	35V	15V	2V @ 1A	0°C ~ 125°C	Active	TO-220-3

Engineering Selection Recommendations

For Direct Functional Replacement (Highest Current Capability)

No substitute part in the active product list provides the full 3A output current of the KA78T15. The closest alternatives are the STMicroelectronics L7815ABV and L7815ACV, each rated for 1.5A output. These parts are active products with ROHS3 compliance and support the full operating temperature range of the original device.

For Standard 1A Applications

Multiple active alternatives exist from onsemi and Diodes Incorporated:

MC7815ACTG (onsemi, 0°C ~ 125°C operating range)
MC7815CTG (onsemi, 0°C ~ 125°C operating range)
AS7815AT-E1 (Diodes Incorporated, -40°C ~ 125°C operating range)

All three are ROHS3 compliant and actively manufactured.

For Extended Temperature Range (-40°C)

If the application requires operation below 0°C, select from:

MC7815ABTG (onsemi, 1A)
MC7815BTG (onsemi, 1A)
AS7815AT-E1 (Diodes Incorporated, 1A)
L7815ABV (STMicroelectronics, 1.5A)

For Reduced Current Requirements (500mA)

MC78M15CTG (onsemi) is the recommended active product for applications requiring only 500mA output, with 0°C ~ 125°C operating range and ROHS3 compliance.

Automotive Grade Consideration

NCV7815BTG is an automotive-qualified part (AEC-Q100) but is obsolete. No active automotive-grade substitute is listed in the provided data.

Frequently Asked Questions (FAQ)

Q: Can I use a 1A-rated part as a direct replacement for the KA78T15 (3A)?

A: No. The KA78T15 is rated for 3A maximum output current. Using a 1A-rated substitute will limit the available current to 1A. This is acceptable only if your application circuit draws 1A or less. Exceeding the rated current will trigger thermal shutdown protection.

Q: What is the difference between MC7815ACTG and MC7815CTG?

A: Both are 1A regulators with identical electrical specifications. The primary difference is the operating temperature range: MC7815ACTG operates 0°C ~ 125°C, while MC7815CTG also operates 0°C ~ 125°C. Both are active products with equivalent availability and ROHS3 compliance.

Q: Why does the KA78T15 have a 40V maximum input while substitutes are rated 35V?

A: The KA78T15 is an obsolete part with a higher input voltage rating. All active substitutes are rated for 35V maximum input. If your application requires 40V input capability, verify that your actual input voltage does not exceed 35V before selecting a substitute.

Q: Is the TO-220-3 package compatible with TO-220 variants?

A: TO-220-3 and TO-220 are mechanically and electrically compatible for three-terminal linear regulators. All substitute parts listed use TO-220-3 or TO-220 packaging and are pin-compatible with the KA78T15.

Q: Can I use L7815ABV instead of KA78T15 for higher current capability?

A: L7815ABV provides 1.5A output, which is still below the KA78T15's 3A rating. However, it is the highest-current active substitute available. If your application requires more than 1.5A, alternative voltage regulation topologies (switching regulators) should be considered.

Q: What does ROHS3 compliance mean for my application?

A: ROHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements, restricting lead and other hazardous materials. All active substitutes listed are ROHS3 compliant, making them suitable for commercial and industrial applications subject to environmental regulations.

Q: Should I choose a part with -40°C to 125°C range or 0°C to 125°C range?

A: Select based on your application's minimum operating temperature. If your circuit operates only above 0°C, either range is acceptable. If operation below 0°C is required, select parts with -40°C minimum rating such as MC7815ABTG, MC7815BTG, AS7815AT-E1, or L7815ABV.

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