LM340T-12 Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The LM340T-12 is a positive fixed linear voltage regulator IC manufactured by Texas Instruments, rated for 12V output at 1.5A in a TO-220-3 package. This device is classified as Last Time Buy, indicating discontinued production. The LM340T-12 provides regulated 12V power from input sources up to 35V with integrated over-temperature and short-circuit protection. Due to its Last Time Buy status, equivalent substitute parts from active manufacturers are necessary for new designs and ongoing production requirements.

Key Parameters

Parameter	LM340T-12
Output Voltage (Fixed)	12V
Output Current	1.5A
Input Voltage (Max)	35V
Voltage Dropout (Max)	2V @ 1A
Quiescent Current	8 mA
PSRR	80dB (120Hz)
Protection Features	Over Temperature, Short Circuit
Operating Temperature Range	0°C ~ 125°C
Package	TO-220-3
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the LM340T-12 is determined by the following critical parameters:

Output Voltage: Must be fixed at 12V
Output Current Capability: Minimum 1.5A for direct replacement; 500mA variants are functional alternatives for lower-current applications
Package Type: TO-220-3 form factor for mechanical and thermal compatibility
Input Voltage Rating: Maximum 35V
Protection Features: Over-temperature and short-circuit protection required
Compliance: ROHS3 compliance and REACH unaffected status

Substitute parts are grouped into two categories:

Direct Equivalents (1.5A Output): Parts with identical 1.5A current rating and 12V output
Functional Alternatives (500mA Output): Parts with reduced current capacity suitable for lower-power applications

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Input Voltage (Max)	Dropout Voltage	Quiescent Current	PSRR	Operating Temp	Product Status
LM340T-12	Texas Instruments	12V	1.5A	35V	2V @ 1A	8 mA	80dB (120Hz)	0°C ~ 125°C	Last Time Buy
LM340T-12/NOPB	Texas Instruments	12V	1.5A	35V	2V @ 1A	8 mA	80dB (120Hz)	0°C ~ 125°C	Active
L7812ABV	STMicroelectronics	12V	1.5A	35V	2V @ 1A (Typ)	6 mA	60dB (120Hz)	-40°C ~ 125°C	Active
L78M12CV	STMicroelectronics	12V	500mA	35V	—	6 mA	55dB (120Hz)	0°C ~ 125°C	Active
MC7812ACTG	onsemi	12V	1A	35V	2V @ 1A (Typ)	6 mA	60dB (1kHz)	0°C ~ 125°C	Active
MC7812BTG	onsemi	12V	1A	35V	2V @ 1A (Typ)	8 mA	60dB (1kHz)	-40°C ~ 125°C	Active
MC7812CTG	onsemi	12V	1A	35V	2V @ 1A (Typ)	6.5 mA	60dB (1kHz)	0°C ~ 125°C	Active
MC78M12ACTG	onsemi	12V	500mA	35V	—	—	80dB (120Hz)	0°C ~ 125°C	Obsolete
MC78M12BTG	onsemi	12V	500mA	35V	—	—	80dB (120Hz)	-40°C ~ 125°C	Active
MC78M12CTG	onsemi	12V	500mA	35V	—	—	80dB (120Hz)	0°C ~ 125°C	Active

Engineering Selection Recommendations

Primary Substitute (Direct Replacement): LM340T-12/NOPB from Texas Instruments is the direct equivalent with identical electrical specifications and Active product status. This part maintains full compatibility with existing designs without modification.

Alternative Substitutes (1.5A Capability): L7812ABV from STMicroelectronics provides 1.5A output with extended operating temperature range (-40°C to 125°C) and Active status. This part is suitable for applications requiring wider temperature operation.

Reduced Current Alternatives (500mA Capability): For applications requiring only 500mA output, the following parts are available:

L78M12CV (STMicroelectronics, Active)
MC78M12BTG (onsemi, Active)
MC78M12CTG (onsemi, Active)

These parts are not suitable for applications requiring the full 1.5A output of the original LM340T-12.

1A Intermediate Options: MC7812ACTG, MC7812BTG, and MC7812CTG from onsemi provide 1A output, which is intermediate between the full 1.5A and 500mA variants. These are suitable only for applications with maximum current draw not exceeding 1A.

All recommended substitutes maintain ROHS3 compliance and REACH unaffected status. Avoid MC78M12ACTG due to Obsolete product status.

Frequently Asked Questions (FAQ)

Q: Can I use a 500mA part as a substitute for the LM340T-12? A: Only if your application draws maximum 500mA. The L78M12CV, MC78M12BTG, and MC78M12CTG are functional alternatives for lower-current designs. Using a 500mA part in a 1.5A application will result in current limiting and potential circuit malfunction.

Q: What is the difference between LM340T-12 and LM340T-12/NOPB? A: Both are Texas Instruments parts with identical electrical specifications. The /NOPB designation indicates lead-free (No Lead) and RoHS compliance. LM340T-12/NOPB is Active, making it the preferred direct replacement.

Q: Are all substitute parts in TO-220-3 package? A: Yes. All listed substitutes use the TO-220-3 package, ensuring mechanical and thermal compatibility with the original LM340T-12.

Q: Can I use MC7812ACTG, MC7812BTG, or MC7812CTG instead of the LM340T-12? A: These onsemi parts provide only 1A output versus the LM340T-12's 1.5A. They are suitable only for applications with maximum current draw not exceeding 1A. Verify your circuit's actual current requirements before substitution.

Q: What is the operating temperature range difference between substitutes? A: The LM340T-12 operates 0°C to 125°C. L7812ABV and MC7812BTG extend to -40°C to 125°C for wider temperature applications. Most other substitutes maintain the 0°C to 125°C range. Select based on your application's thermal requirements.

Q: Why is MC78M12ACTG listed but marked Obsolete? A: MC78M12ACTG is included for reference in legacy designs but should not be selected for new applications. Use MC78M12BTG or MC78M12CTG instead for 500mA 12V regulation.

Q: Do all substitutes have the same protection features? A: All listed substitutes include over-temperature and short-circuit protection. Some variants add over-current protection. Verify specific protection requirements for your application.

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