LM78T12CT Linear Voltage Regulator Equivalent & Substitute Parts

Part Overview

The LM78T12CT is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 12V output at 3A maximum current. This through-hole TO-220-3 package component is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The LM78T12CT serves as a positive fixed voltage regulator suitable for power management applications requiring stable 12V regulation with integrated over-temperature and short-circuit protection.

Key Parameters

Parameter	LM78T12CT
Manufacturer	onsemi
Output Voltage (Fixed)	12V
Output Current	3A
Input Voltage (Max)	35V
Voltage Dropout (Max)	2.5V @ 3A
Quiescent Current	6 mA
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 of the LM78T12CT is determined by the following critical parameters:

Fixed output voltage of 12V
TO-220-3 package and through-hole mounting compatibility
Positive output configuration
Over-temperature and short-circuit protection features
Maximum input voltage rating of 32V or higher
Operating temperature range compatibility

Substitute parts are grouped based on output current capability. The LM78T12CT delivers 3A maximum output current. Substitute parts with lower current ratings (1A, 1.2A, 1.5A) are functionally compatible for applications requiring less than their rated current. Parts with equal or higher current ratings provide direct substitution without derating.

Parameter Comparison

Parameter	LM78T12CT	AS7812AT-E1	L7812ABV	L7812ACV	L7812CV	L7812CV-DG
Manufacturer	onsemi	Diodes Incorporated	STMicroelectronics	STMicroelectronics	UMW	STMicroelectronics
Output Voltage	12V	12V	12V	12V	12V	12V
Output Current	3A	1A	1.5A	1.5A	1.2A	1.5A
Input Voltage (Max)	35V	32V	35V	35V	35V	35V
Voltage Dropout (Max)	2.5V @ 3A	2V @ 1A (Typ)	2V @ 1A (Typ)	2V @ 1A (Typ)	Not specified	2V @ 1A (Typ)
Quiescent Current	6 mA	6 mA	6 mA	6 mA	6 mA	8 mA
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3
Operating Temperature	0°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	0°C ~ 125°C	-40°C ~ 105°C	0°C ~ 125°C
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

All substitute parts listed are active products with ROHS3 compliance, ensuring regulatory alignment for new designs. The LM78T12CT is obsolete; therefore, selection of an active substitute is mandatory for production continuity.

For applications requiring the full 3A output current of the LM78T12CT, no direct equivalent with identical current rating is available among the listed substitutes. In such cases, external current boosting circuitry or selection of a higher-capacity regulator from alternative product lines is required.

For applications operating within 1A to 1.5A output current range, L7812CV-DG (STMicroelectronics, 1.5A) and L7812ABV (STMicroelectronics, 1.5A) provide the closest electrical match with maximum input voltage of 35V and operating temperature range of 0°C to 125°C.

AS7812AT-E1 (Diodes Incorporated, 1A) is suitable for lower-current applications but has a reduced maximum input voltage of 32V, requiring verification against circuit input voltage specifications.

L7812CV (UMW, 1.2A) operates at a reduced maximum temperature of 105°C, limiting use in applications requiring the full 0°C to 125°C range.

All substitute parts maintain TO-220-3 through-hole packaging, ensuring mechanical compatibility with existing PCB layouts.

Frequently Asked Questions (FAQ)

Q: Can I use a substitute part with lower output current rating than the LM78T12CT?

A: Yes, if your application draws less current than the substitute part's rating. For example, if your circuit requires 1.5A maximum, L7812ABV or L7812CV-DG are suitable. However, if your circuit requires the full 3A, no listed substitute is directly compatible without external current boosting.

Q: Are all substitute parts pin-compatible with the LM78T12CT?

A: Yes. All listed substitutes use the TO-220-3 package with identical pin configuration: input, ground, and output. Direct PCB replacement is possible without layout modification.

Q: What is the difference between L7812ABV and L7812ACV?

A: Both are STMicroelectronics parts with identical electrical specifications (12V, 1.5A, 35V max input). The primary difference is operating temperature range: L7812ABV operates from -40°C to 125°C, while L7812ACV operates from 0°C to 125°C. Select based on your minimum operating temperature requirement.

Q: Why does L7812CV-DG have 8 mA quiescent current instead of 6 mA?

A: Quiescent current variation within this range is typical across different manufacturers and process nodes. This 2 mA difference has negligible impact on most applications and does not affect functional compatibility.

Q: Is AS7812AT-E1 suitable for my 35V input application?

A: AS7812AT-E1 has a maximum input voltage rating of 32V. If your circuit input exceeds 32V, this part is not suitable. Verify your actual input voltage specification before selection.

Q: Can I use these substitutes in applications requiring -40°C operation?

A: Only AS7812AT-E1 and L7812ABV are rated for -40°C minimum temperature. L7812ACV, L7812CV-DG, and L7812CV have higher minimum temperature ratings and are not suitable for -40°C operation.

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