LTP300F Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The LTP300F is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 24V maximum voltage with a 3A hold current. This component is classified as obsolete, making identification of active equivalent parts essential for ongoing design support and procurement continuity. The LTP300F operates within a temperature range of -40°C to 85°C and is housed in a user-defined strap package measuring 30.10mm × 13.25mm. Due to its obsolete status, sourcing active alternatives with identical electrical and mechanical specifications is necessary for system maintenance and new production requirements.

Key Parameters

Parameter	LTP300F Specification
Voltage - Max	24V
Current - Hold (Ih) (Max)	3 A
Current - Trip (It)	6.3 A
Current - Max	100 A
Time to Trip	4 s
Resistance - Initial (Ri) (Min)	15 mOhms
Resistance - Post Trip (R1) (Max)	55 mOhms
Operating Temperature	-40°C ~ 85°C
Type	Polymeric
Package / Case	Strap
Size / Dimension	1.185" L x 0.522" W (30.10mm x 13.25mm)
Thickness (Max)	0.043" (1.10mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the LTP300F is determined by strict equivalence across the following critical parameters:

Voltage rating: 24V maximum
Hold current (Ih): 3A maximum
Trip current (It): 6.3A
Maximum current capacity: 100A
Time to trip: 4 seconds
Initial resistance (Ri): 15 mOhms minimum
Post-trip resistance (R1): 55 mOhms maximum
Operating temperature range: -40°C to 85°C
Package type: Strap configuration
Physical dimensions: 30.10mm × 13.25mm × 1.10mm maximum thickness
Polymeric PTC resettable fuse technology

The MF-LS300 from Bourns Inc. meets all specified electrical and mechanical parameters, making it a direct functional equivalent for the obsolete LTP300F.

Parameter Comparison

Parameter	LTP300F (Littelfuse)	MF-LS300 (Bourns)	Match Status
Voltage - Max	24V	24V	Identical
Current - Hold (Ih) (Max)	3 A	3 A	Identical
Current - Trip (It)	6.3 A	6.3 A	Identical
Current - Max	100 A	100 A	Identical
Time to Trip	4 s	4 s	Identical
Resistance - Initial (Ri) (Min)	15 mOhms	15 mOhms	Identical
Resistance - Post Trip (R1) (Max)	55 mOhms	55 mOhms	Identical
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	Identical
Type	Polymeric	Polymeric	Identical
Package / Case	Strap	Strap	Identical
Size / Dimension	30.10mm x 13.25mm	30.10mm x 13.25mm	Identical
Thickness (Max)	1.10mm	1.10mm	Identical
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Identical
Product Status	Obsolete	Active	Substitute is active

Engineering Selection Recommendations

The MF-LS300 is the appropriate substitute for the obsolete LTP300F based on the following factors:

All electrical parameters are identical, including voltage rating, hold current, trip current, time to trip, and resistance specifications. Physical dimensions and package configuration match exactly, ensuring direct mechanical compatibility in existing designs. Both components are ROHS3 compliant and carry equivalent regulatory approvals (CSA, TUV, UL for LTP300F; cURus, TUV for MF-LS300). The MF-LS300 maintains active product status with Bourns Inc., ensuring long-term availability and supply chain continuity. The MF-LS300 offers improved moisture sensitivity rating (MSL 1 Unlimited versus MSL 2A for LTP300F), providing enhanced reliability in storage and handling conditions.

Frequently Asked Questions (FAQ)

Q: Can the MF-LS300 be used as a direct replacement for the LTP300F in existing designs?

A: Yes. The MF-LS300 meets all electrical and mechanical specifications of the LTP300F, including voltage rating, current ratings, resistance values, operating temperature range, and physical dimensions. No circuit modifications are required.

Q: Are there any differences in regulatory approvals between these parts?

A: Both components carry TUV certification. The LTP300F includes CSA and UL approvals, while the MF-LS300 carries cURus and TUV approvals. Verify that the MF-LS300 certifications meet your specific application requirements.

Q: What is the difference in moisture sensitivity between these parts?

A: The LTP300F has MSL 2A (4 weeks), while the MF-LS300 has MSL 1 (Unlimited). The MF-LS300 offers superior moisture resistance and longer shelf life without special storage conditions.

Q: Are the strap package dimensions identical?

A: Yes. Both components measure 30.10mm length × 13.25mm width × 1.10mm maximum thickness, ensuring identical mechanical fit in strap-mounted applications.

Q: What is the current availability status of each part?

A: The LTP300F is obsolete with limited remaining inventory (935 pieces). The MF-LS300 is an active product with current inventory (988 pieces) and ongoing manufacturing support from Bourns Inc.

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