LM340T-15 Linear Voltage Regulator Equivalent & Substitute Parts

Part Overview

The LM340T-15 is a linear voltage regulator IC manufactured by Texas Instruments, delivering a fixed positive 15V output at 1.5A in a TO-220-3 package. This device is classified as Last Time Buy, indicating discontinued production. The part provides positive output configuration with integrated over-temperature and short-circuit protection, suitable for power management applications requiring fixed 15V regulation.

Substitute parts are necessary due to the Last Time Buy status of the LM340T-15. Alternative models from active product lines ensure design continuity and long-term supply availability.

Key Parameters

Parameter	LM340T-15
Output Voltage (Fixed)	15V
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	0°C ~ 125°C
Package	TO-220-3
Product Status	Last Time Buy

Substitute Part Grouping Explanation

Substitution eligibility is determined by the following criteria applied strictly to the provided parameters:

Primary Substitution Criteria:

Fixed output voltage of 15V
Output current rating equal to or greater than 1.5A
Maximum input voltage of 35V or higher
TO-220-3 package configuration
Positive output configuration
Over-temperature and short-circuit protection

Secondary Compatibility Factors:

Voltage dropout characteristics
Quiescent current specifications
PSRR performance at 120Hz
Operating temperature range compatibility

Substitute parts are grouped into two categories based on output current capability: full-current substitutes (1.5A or higher) and reduced-current alternatives (500mA to 1A). Full-current substitutes maintain identical output current specifications. Reduced-current alternatives are listed for reference but require circuit design verification due to lower current capacity.

Parameter Comparison

Part Number	Manufacturer	Output Current	Voltage Dropout (Max)	Quiescent Current	PSRR (120Hz)	Operating Temp	Product Status	RoHS Status
LM340T-15	Texas Instruments	1.5A	2V @ 1A	8 mA	80dB	0°C ~ 125°C	Last Time Buy	Non-compliant
LM340T-15/NOPB	Texas Instruments	1.5A	2V @ 1A	8 mA	80dB	0°C ~ 125°C	Active	ROHS3 Compliant
L7815ABV	STMicroelectronics	1.5A	2V @ 1A (Typ)	6 mA	58dB	-40°C ~ 125°C	Active	ROHS3 Compliant
L78M15ABV	STMicroelectronics	500mA	—	6 mA	54dB	-40°C ~ 125°C	Obsolete	ROHS3 Compliant
L78M15CV	STMicroelectronics	500mA	—	6 mA	54dB	0°C ~ 125°C	Obsolete	ROHS3 Compliant
L78S15CV	STMicroelectronics	2A	—	8 mA	46dB	0°C ~ 150°C	Obsolete	ROHS3 Compliant
MC7815ABTG	onsemi	1A	2V @ 1A (Typ)	6 mA	80dB	-40°C ~ 125°C	Active	ROHS3 Compliant
MC7815ACTG	onsemi	1A	2V @ 1A (Typ)	6 mA	80dB	0°C ~ 125°C	Active	ROHS3 Compliant
MC7815BTG	onsemi	1A	2V @ 1A (Typ)	8 mA	58dB	-40°C ~ 125°C	Active	ROHS3 Compliant
MC7815CTG	onsemi	1A	2V @ 1A (Typ)	6.5 mA	58dB	0°C ~ 125°C	Active	ROHS3 Compliant
MC78M15ABTG	onsemi	500mA	—	—	70dB	-40°C ~ 125°C	Obsolete	ROHS3 Compliant

Engineering Selection Recommendations

Recommended Primary Substitute: LM340T-15/NOPB

The LM340T-15/NOPB is the direct equivalent from Texas Instruments with identical electrical specifications and full 1.5A output current capability. This part maintains the same performance characteristics as the original LM340T-15 while offering Active product status and ROHS3 compliance. Selection of this part eliminates any design verification requirements.

Recommended Alternative Substitute: L7815ABV

The L7815ABV from STMicroelectronics provides full 1.5A output current with Active product status and ROHS3 compliance. This part maintains equivalent voltage dropout and PSRR performance. The extended operating temperature range (-40°C to 125°C) provides additional thermal margin compared to the original part. This substitute is suitable for applications where extended temperature operation is beneficial.

Reduced-Current Alternatives:

The MC7815ABTG, MC7815ACTG, MC7815BTG, and MC7815CTG from onsemi deliver 1A output current with Active product status and ROHS3 compliance. These parts are suitable only for applications where the load current does not exceed 1A. Circuit design verification is required to confirm load current compatibility before selection.

The L78M15ABV, L78M15CV, L78S15CV, and MC78M15ABTG are Obsolete products and are not recommended for new designs despite ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can the MC7815ABTG replace the LM340T-15 in all applications?

A: The MC7815ABTG provides only 1A output current compared to the LM340T-15's 1.5A rating. Substitution is valid only if the circuit load current does not exceed 1A. Verify the maximum load current requirement before selection.

Q: What is the difference between LM340T-15 and LM340T-15/NOPB?

A: Both parts are electrically identical with matching specifications. The LM340T-15/NOPB is the current production version with Active status and ROHS3 compliance, while the original LM340T-15 is Last Time Buy. The /NOPB designation indicates lead-free manufacturing.

Q: Are the STMicroelectronics L78M15 series parts suitable substitutes?

A: The L78M15ABV and L78M15CV deliver only 500mA output current, which is insufficient for applications requiring the full 1.5A capability of the LM340T-15. These parts are not recommended as direct substitutes. The L7815ABV from STMicroelectronics is the appropriate choice for full-current replacement.

Q: Does the L7815ABV have better performance than the LM340T-15?

A: The L7815ABV maintains equivalent voltage dropout and input voltage specifications. The PSRR is 58dB compared to the LM340T-15's 80dB, representing a reduction in power supply rejection ratio. The quiescent current is lower at 6mA versus 8mA. The extended operating temperature range (-40°C to 125°C) provides additional thermal capability.

Q: Can I use the L78S15CV for higher current applications?

A: The L78S15CV provides 2A output current, exceeding the LM340T-15's 1.5A rating. However, this part is Obsolete and not recommended for new designs. The L7815ABV is the preferred choice for active product availability with full 1.5A capability.

Q: Are all substitute parts RoHS compliant?

A: All recommended substitute parts are ROHS3 compliant. The original LM340T-15 is RoHS non-compliant. The LM340T-15/NOPB and all STMicroelectronics and onsemi alternatives meet ROHS3 requirements.

Q: What is the package compatibility between these parts?

A: All listed parts use the TO-220-3 package configuration, ensuring mechanical and thermal compatibility. Pin assignments are identical across all substitutes, allowing direct board-level replacement without layout modifications.

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