Equivalent & Substitute Parts for 24LT100U

Part Overview

The 24LT100U is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 24V maximum voltage with 1 A hold current. This component is classified as obsolete, making identification of equivalent and substitute parts essential for ongoing system support and component procurement. The 24LT100U operates across a temperature range of -40°C to 85°C and is packaged as a user-defined strap configuration with dimensions of 22.00mm × 5.05mm.

Key Parameters

Parameter	Value
Voltage - Max	24V
Current - Hold (Ih) (Max)	1 A
Current - Trip (It)	2.5 A
Current - Max	100 A
Time to Trip	7 s
Resistance - Initial (Ri) (Min)	70 mOhms
Resistance - Post Trip (R1) (Max)	260 mOhms
Operating Temperature	-40°C ~ 85°C
Type	Polymeric
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the 24LT100U is determined by electrical and mechanical compatibility across the following critical parameters: maximum voltage rating, hold current (Ih), trip current (It), maximum current capacity, operating temperature range, and RoHS compliance status. All identified substitutes maintain the 24V maximum voltage rating and -40°C to 85°C operating temperature range. Substitutes are grouped into two categories based on mounting configuration and current handling characteristics.

Category 1: Direct Electrical Equivalent (Strap Mount) The MF-LS100 from Bourns Inc. provides direct electrical equivalence with identical hold current (1 A), trip current (2.5 A), time to trip (7 s), and resistance specifications. This part maintains the same strap mounting configuration and physical dimensions (22.00mm × 5.05mm).

Category 2: Functional Equivalent (Surface Mount) The MINISMDC050F-2 from Littelfuse provides functional equivalence at reduced current levels. While the hold current is reduced to 500 mA and trip current to 1 A, this part maintains the 24V voltage rating and operating temperature range. The surface mount 1812 (4532 Metric) package represents a different mounting technology suitable for applications where strap mounting is not required.

Parameter Comparison

Parameter	24LT100U (Main)	MF-LS100 (Bourns)	MINISMDC050F-2 (Littelfuse)
Manufacturer	Littelfuse Inc.	Bourns Inc.	Littelfuse
Product Status	Obsolete	Active	Active
Voltage - Max	24V	24V	24V
Current - Hold (Ih) (Max)	1 A	1 A	500 mA
Current - Trip (It)	2.5 A	2.5 A	1 A
Current - Max	100 A	100 A	100 A
Time to Trip	7 s	7 s	150 ms
Resistance - Initial (Ri) (Min)	70 mOhms	70 mOhms	150 mOhms
Resistance - Post Trip (R1) (Max)	260 mOhms	260 mOhms	1 Ohms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Type	Polymeric	Polymeric	Polymeric
Mounting Type	User Defined (Strap)	User Defined (Strap)	Surface Mount
Package / Case	Strap	Strap	1812 (4532 Metric), Concave
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	cURus, TUV	CSA, TUV, UR	CSA, TUV, UL

Engineering Selection Recommendations

For Direct Replacement (Strap Mount Applications): The MF-LS100 from Bourns Inc. is the primary substitute for the obsolete 24LT100U. This part maintains identical electrical specifications including 1 A hold current, 2.5 A trip current, 7 second time to trip, and 70 mOhms initial resistance. Both parts share the same strap mounting configuration and physical dimensions. The MF-LS100 carries active product status with CSA, TUV, and UR certifications, ensuring continued availability and regulatory compliance.

For Surface Mount Applications: The MINISMDC050F-2 from Littelfuse provides a surface mount alternative for designs that can accommodate reduced current specifications. This part is suitable for applications where the 24LT100U's 1 A hold current requirement can be reduced to 500 mA. The MINISMDC050F-2 features a faster response time (150 ms versus 7 s) and is available in high volume with active product status. This substitute requires circuit redesign to accommodate the lower current ratings and surface mount 1812 package format.

Frequently Asked Questions (FAQ)

Q: Can the MF-LS100 be used as a direct replacement for the 24LT100U? A: Yes. The MF-LS100 provides direct electrical and mechanical equivalence with identical voltage rating (24V), hold current (1 A), trip current (2.5 A), time to trip (7 s), and resistance specifications. Both parts use strap mounting with identical physical dimensions (22.00mm × 5.05mm).

Q: What are the key differences between the MF-LS100 and MINISMDC050F-2? A: The MF-LS100 maintains the original 1 A hold current and 7 second trip time in a strap configuration. The MINISMDC050F-2 reduces hold current to 500 mA, reduces trip current to 1 A, and significantly reduces trip time to 150 ms. The MINISMDC050F-2 uses surface mount 1812 (4532 Metric) packaging instead of strap mounting.

Q: Is the MINISMDC050F-2 suitable for all applications using the 24LT100U? A: No. The MINISMDC050F-2 is suitable only for applications where the circuit can operate with 500 mA hold current instead of 1 A, and where the faster 150 ms trip time is acceptable or beneficial. The surface mount package also requires compatible PCB design.

Q: What certifications do the substitute parts carry? A: The MF-LS100 carries CSA, TUV, and UR certifications. The MINISMDC050F-2 carries CSA, TUV, and UL certifications. Both parts are ROHS3 compliant.

Q: Are both substitute parts currently available? A: Yes. The MF-LS100 from Bourns carries active product status with 2718 pieces in stock. The MINISMDC050F-2 from Littelfuse carries active product status with 805200 pieces in stock.

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