LM78M24CT Linear Voltage Regulator 24V 500mA Equivalent & Substitute Parts

Part Overview

The LM78M24CT is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 24V output at 500mA in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing production and maintenance applications. The LM78M24CT serves as a positive fixed output regulator suitable for power management applications requiring stable 24V regulation with thermal and short-circuit protection.

Key Parameters

Parameter	Value
Manufacturer Part Number	LM78M24CT
Manufacturer	onsemi
Category	Power Management (PMIC)
Output Configuration	Positive Fixed
Voltage - Output (Fixed)	24V
Current - Output	500mA
Voltage - Input (Max)	40V
Voltage Dropout (Max)	2V @ 500mA (Typ)
Current - Quiescent (Iq)	6 mA
PSRR	70dB (120Hz)
Protection Features	Over Temperature, Short Circuit
Operating Temperature	0°C ~ 125°C
Package / Case	TO-220-3
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the LM78M24CT is determined by the following critical parameters:

Fixed output voltage of 24V
Through-hole TO-220-3 package compatibility
Output current capability (500mA minimum)
Maximum input voltage rating (40V)
Protection features (Over Temperature, Short Circuit)
Operating temperature range overlap

Substitute parts are grouped into two categories:

Parametric Equivalents (500mA Output Current): Parts with identical 500mA output current rating, matching the LM78M24CT specification exactly.

Higher Current Alternatives (1A or 1.5A Output Current): Parts with increased output current capability that maintain all other critical parameters, suitable for applications with headroom requirements or future design flexibility.

Parameter Comparison

Part Number	Manufacturer	Output Current	Voltage - Input (Max)	Voltage Dropout (Max)	Current - Quiescent (Iq)	PSRR (120Hz)	Operating Temperature	Package	Product Status
LM78M24CT	onsemi	500mA	40V	2V @ 500mA	6 mA	70dB	0°C ~ 125°C	TO-220-3	Obsolete
MC78M24CTG	onsemi	500mA	40V	Not specified	6.5 mA	70dB	0°C ~ 125°C	TO-220-3	Obsolete
BA178M24T	Rohm Semiconductor	500mA	33V	2V @ 500mA	4.5 mA	55dB	-40°C ~ 85°C	TO-220-3 Full Pack	Not For New Designs
L78M24CV	STMicroelectronics	500mA	40V	Not specified	6 mA	50dB	0°C ~ 125°C	TO-220-3	Active
MC7824CTG	onsemi	1A	40V	2V @ 1A	6.5 mA	61dB	0°C ~ 125°C	TO-220-3	Active
MC7824BTG	onsemi	1A	40V	2V @ 1A	8 mA	61dB	-40°C ~ 125°C	TO-220-3	Active
L7824CV	STMicroelectronics	1.5A	40V	2V @ 1A	8 mA	50dB	0°C ~ 125°C	TO-220-3	Active
L7824CV-DG	STMicroelectronics	1.5A	40V	2V @ 1A	8 mA	50dB	0°C ~ 125°C	TO-220-3	Active
L7824ABV	STMicroelectronics	1.5A	40V	2V @ 1A	6 mA	54dB	-40°C ~ 125°C	TO-220-3	Active
L7824ABV-DG	STMicroelectronics	1.5A	40V	2V @ 1A	6 mA	54dB	-40°C ~ 125°C	TO-220-3	Active
L7824ACV	STMicroelectronics	1.5A	40V	2V @ 1A	6 mA	54dB	0°C ~ 125°C	TO-220-3	Obsolete

Engineering Selection Recommendations

Direct Parametric Equivalent (Recommended for Drop-In Replacement):

L78M24CV (STMicroelectronics) is the primary recommended substitute. This part maintains the 500mA output current specification, 40V maximum input voltage, and 0°C to 125°C operating temperature range. The device is currently in active production status with RoHS3 compliance and REACH unaffected certification. Inventory availability is adequate at 4,612 pieces.

Alternative Parametric Equivalent:

MC78M24CTG (onsemi) provides identical 500mA output current and operating temperature range. Although obsolete status matches the original part, this option maintains full parameter compatibility. PSRR performance is equivalent at 70dB.

Higher Current Alternatives (1A Output):

MC7824CTG and MC7824BTG (onsemi) offer doubled output current capacity at 1A while maintaining 40V input rating and TO-220-3 package. Both are in active production. MC7824CTG operates 0°C to 125°C; MC7824BTG extends to -40°C to 125°C. These are suitable when circuit design permits higher current capability.

Higher Current Alternatives (1.5A Output):

L7824CV, L7824CV-DG, L7824ABV, and L7824ABV-DG (STMicroelectronics) provide 1.5A output current with 40V input rating. All are in active production with RoHS3 compliance. L7824ABV and L7824ABV-DG extend operating temperature to -40°C to 125°C. These options provide maximum current headroom for demanding applications.

Not Recommended:

BA178M24T (Rohm Semiconductor) is marked "Not For New Designs" and has reduced maximum input voltage (33V) and narrower operating temperature range (-40°C to 85°C). This part should be avoided for new designs.

Frequently Asked Questions (FAQ)

Q: Can I use a 1A or 1.5A rated regulator as a direct replacement for the 500mA LM78M24CT?

A: Yes. Higher current-rated regulators (MC7824CTG, L7824CV, L7824ABV) are electrically compatible substitutes. The 500mA circuit will operate within the regulator's capability. The higher current rating provides design margin and does not negatively affect circuit performance at lower current draw.

Q: What is the difference between L7824CV and L7824CV-DG?

A: Both parts are identical in electrical specifications and performance. The "-DG" suffix indicates a different distribution channel or packaging configuration. Functionally, they are equivalent for circuit design purposes.

Q: Is the BA178M24T suitable as a substitute?

A: No. The BA178M24T has a maximum input voltage of 33V compared to the LM78M24CT's 40V specification. Additionally, it is marked "Not For New Designs" by the manufacturer. Use L78M24CV or MC78M24CTG instead.

Q: Do all substitute parts use the same TO-220-3 package?

A: Yes. All listed substitute parts use TO-220-3 through-hole packaging, ensuring mechanical and thermal compatibility with existing PCB layouts and heat sink mounting.

Q: What is the significance of PSRR (Power Supply Rejection Ratio)?

A: PSRR measures how effectively the regulator rejects input voltage ripple and noise. The LM78M24CT has 70dB PSRR at 120Hz. L78M24CV has 50dB, which is still adequate for most applications but provides slightly

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