KA78T05 Linear Voltage Regulator - Equivalent & Substitute Parts

Part Overview

The KA78T05 is a linear voltage regulator IC manufactured by onsemi, providing a fixed positive 5V output at 3A in a TO-220-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support. The KA78T05 serves applications requiring stable 5V regulation from input sources up to 35V with integrated over-temperature and short-circuit protection.

Key Parameters

Parameter	Value
Manufacturer Part Number	KA78T05
Manufacturer	onsemi
Output Voltage (Fixed)	5V
Output Current	3A
Input Voltage (Max)	35V
Voltage Dropout (Max)	2.5V @ 3A
Package / Case	TO-220-3
Mounting Type	Through Hole
Operating Temperature	0°C ~ 125°C
Protection Features	Over Temperature, Short Circuit
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the KA78T05 is determined by the following critical parameters:

Output Voltage: Must be fixed at 5V
Package / Case: Must be TO-220-3 for mechanical and thermal compatibility
Output Current Capability: Minimum 3A required to match or exceed the original specification
Input Voltage Rating: Must support maximum 35V input
Protection Features: Over-temperature and short-circuit protection required
Mounting Type: Through-hole configuration mandatory

Substitute parts are grouped into two categories:

Category A - Direct Equivalents (3A Output Current): Parts meeting or exceeding the full 3A output specification with identical electrical characteristics.

Category B - Reduced Current Alternatives (1A to 1.5A Output Current): Parts with lower output current ratings suitable for applications with reduced power requirements. These are not direct replacements for 3A-rated designs but serve as alternatives for lower-current applications.

Category C - Lower Current Alternatives (500mA Output Current): Parts with significantly reduced output current, applicable only to low-power designs.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Voltage Dropout (Max)	Package	Operating Temp	Product Status
KA78T05	onsemi	5V	3A	35V	2.5V @ 3A	TO-220-3	0°C ~ 125°C	Obsolete
MC7805ACTG	onsemi	5V	1A	35V	2V @ 1A	TO-220-3	0°C ~ 125°C	Active
MC7805BTG	onsemi	5V	1A	35V	2V @ 1A	TO-220-3	-40°C ~ 125°C	Active
MC7805CTG	onsemi	5V	1A	35V	2V @ 1A	TO-220-3	0°C ~ 125°C	Active
MC78M05ACTG	onsemi	5V	500mA	35V	Not Specified	TO-220-3	0°C ~ 125°C	Obsolete
MC78M05BTG	onsemi	5V	500mA	35V	Not Specified	TO-220-3	-40°C ~ 125°C	Active
MC78M05CTG	onsemi	5V	500mA	35V	Not Specified	TO-220-3	0°C ~ 125°C	Active
NCV7805BTG	onsemi	5V	1A	35V	2V @ 1A	TO-220-3	-40°C ~ 125°C	Obsolete
L7805ABV	STMicroelectronics	5V	1.5A	35V	2V @ 1A	TO-220-3	-40°C ~ 125°C	Active
L7805ACV	STMicroelectronics	5V	1.5A	35V	2V @ 1A	TO-220-3	0°C ~ 125°C	Active
L7805CV	UMW	5V	1.2A	35V	Not Specified	TO-220-3	-40°C ~ 105°C	Active

Engineering Selection Recommendations

For Active Production (Recommended Primary Choices):

The L7805ABV and L7805ACV from STMicroelectronics are the preferred substitutes. Both deliver 1.5A output current in an active product status with full RoHS3 compliance. The L7805ABV supports the extended temperature range of -40°C to 125°C, matching the thermal capabilities of the original KA78T05. The L7805ACV operates from 0°C to 125°C. Both parts maintain the TO-220-3 package and 35V maximum input rating.

For applications requiring only 1A output current, the MC7805BTG from onsemi is an active alternative with extended temperature range (-40°C to 125°C) and RoHS3 compliance. The MC7805CTG provides the same 1A capability with standard temperature range (0°C to 125°C).

For Extended Temperature Applications:

The MC7805BTG and L7805ABV both support -40°C to 125°C operation, suitable for industrial and automotive environments where the standard 0°C to 125°C range is insufficient.

For Lower Current Requirements:

The MC78M05BTG and MC78M05CTG deliver 500mA output in active status with RoHS3 compliance. These are suitable only for applications with reduced power demands and cannot replace the KA78T05 in 3A-rated designs.

Compliance Considerations:

All recommended active substitutes carry RoHS3 compliance and REACH Unaffected status, meeting modern environmental and regulatory requirements. The NCV7805BTG, while obsolete, carries AEC-Q100 automotive qualification if legacy automotive applications require this certification.

Frequently Asked Questions (FAQ)

Q: Can the MC7805BTG directly replace the KA78T05 in a 3A application?

A: No. The MC7805BTG is rated for 1A maximum output current, while the KA78T05 delivers 3A. Using a 1A regulator in a 3A design will cause thermal shutdown and circuit failure. The L7805ABV or L7805ACV are required for 3A applications.

Q: What is the difference between MC7805ACTG, MC7805BTG, and MC7805CTG?

A: All three deliver 1A output at 5V in TO-220-3 packages. The primary differences are operating temperature range and product status. MC7805BTG supports -40°C to 125°C (extended range, active). MC7805CTG supports 0°C to 125°C (standard range, active). MC7805ACTG supports 0°C to 125°C (standard range, active). Temperature range selection depends on the application environment.

Q: Are the L7805 series parts from STMicroelectronics compatible with onsemi designs?

A: Yes. The L7805ABV and L7805ACV are pin-compatible TO-220-3 regulators with identical electrical specifications (5V output, 1.5A current, 35V maximum input). Both manufacturers follow the same industry standard pinout and functional characteristics for this regulator class.

Q: Why is the KA78T05 obsolete?

A: The KA78T05 is classified as obsolete by onsemi. Active alternatives from both onsemi (MC7805 series) and STMicroelectronics (L7805 series) provide equivalent or superior performance with ongoing manufacturing support and modern compliance certifications.

Q: Can I use the MC78M05 series (500mA) as a substitute?

A: Only if your application requires 500mA or less. The MC78M05 series cannot supply 3A and is not a direct replacement for the KA78T05. Verify actual current requirements before selecting a lower-rated alternative.

Q: What is the thermal difference between the KA78T05 and L7805ABV?

A: Both parts are housed in TO-220-3 packages with identical thermal characteristics. The L7805ABV supports extended temperature operation (-40°C to 125°C) compared to the KA78T05 standard range (0°C to 125°C), making it suitable for wider environmental conditions.

Q: Are all substitute parts RoHS3 compliant?

A: All active substitute parts listed (MC7805 series, L7805 series, MC78M05 series) carry RoHS3 compliance. The obsolete parts (KA78T05, MC78M05ACTG, NCV7805BTG) have varying compliance status. Verify compliance requirements for your specific application before final selection.

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