LTP180LF Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The LTP180LF is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 24V with a 1.8 A hold current. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing design support and procurement. The LTP180LF operates within the -40°C to 85°C temperature range and is housed in a strap package configuration. Substitute parts must maintain electrical compatibility across voltage, current ratings, and thermal characteristics while meeting the same regulatory approvals.

Key Parameters

Parameter	LTP180LF Value
Voltage - Max	24V
Current - Hold (Ih) (Max)	1.8 A
Current - Trip (It)	3.8 A
Current - Max	100 A
Time to Trip	2.9 s
Resistance - Initial (Ri) (Min)	40 mOhms
Resistance - Post Trip (R1) (Max)	120 mOhms
Operating Temperature	-40°C ~ 85°C
Package / Case	Strap
Type	Polymeric
RoHS Status	ROHS3 Compliant
Approval Agency	CSA, TUV, UL

Substitute Part Grouping Explanation

Substitution eligibility for the LTP180LF is determined by the following criteria:

Mandatory Compatibility Parameters:

Voltage rating: 24V maximum
Package type: Strap configuration
Operating temperature range: -40°C to 85°C
Type: Polymeric PTC resettable fuse
RoHS compliance: ROHS3 Compliant

Current Rating Tolerance: Substitute parts are grouped by hold current (Ih) proximity to the original 1.8 A specification. The LTP180LF trip current of 3.8 A and time-to-trip of 2.9 s establish the baseline response characteristics. Substitute parts with hold currents ranging from 1.0 A to 3.4 A are acceptable alternatives, provided they maintain the same voltage and temperature ratings.

Regulatory Alignment: All substitute parts must maintain CSA, TUV, or equivalent certifications. The LTP180LF carries UL, CSA, and TUV approvals; substitute parts must carry at least TUV and cURus certifications to ensure regulatory continuity.

Parameter Comparison

Parameter	LTP180LF	MF-LS100	MF-LS190	MF-LS260	MF-LS300	MF-LS340
Manufacturer	Littelfuse Inc.	Bourns Inc.	Bourns Inc.	Bourns Inc.	Bourns Inc.	Bourns Inc.
Voltage - Max	24V	24V	24V	24V	24V	24V
Current - Hold (Ih) (Max)	1.8 A	1 A	1.9 A	2.6 A	3 A	3.4 A
Current - Trip (It)	3.8 A	2.5 A	4.2 A	5.2 A	6.3 A	6.8 A
Current - Max	100 A	100 A	100 A	100 A	100 A	100 A
Time to Trip	2.9 s	7 s	3 s	5 s	4 s	5 s
Resistance - Initial (Ri) (Min)	40 mOhms	70 mOhms	30 mOhms	25 mOhms	15 mOhms	16 mOhms
Resistance - Post Trip (R1) (Max)	120 mOhms	260 mOhms	100 mOhms	76 mOhms	55 mOhms	50 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	Strap	Strap	Strap	Strap	Strap	Strap
Type	Polymeric	Polymeric	Polymeric	Polymeric	Polymeric	Polymeric
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UL	CSA, TUV, UR	cURus, TUV	cURus, TUV	cURus, TUV	cURus, TUV

Engineering Selection Recommendations

Primary Substitute: MF-LS190

The MF-LS190 is the closest electrical equivalent to the LTP180LF. It maintains a 24V rating, 1.9 A hold current (0.1 A above the original), and 4.2 A trip current (0.4 A above the original). The MF-LS190 carries cURus and TUV certifications, meeting regulatory requirements. This part is active in production and widely available. The 3 s time-to-trip is marginally faster than the LTP180LF's 2.9 s specification, with lower post-trip resistance (100 mOhms vs. 120 mOhms), resulting in improved thermal recovery characteristics.

Secondary Substitute: MF-LS100

The MF-LS100 offers the lowest hold current at 1 A, suitable for applications requiring more sensitive protection. It carries CSA and TUV certifications, directly matching the LTP180LF's approval agencies. The 7 s time-to-trip is significantly longer, making this part appropriate only for circuits tolerating extended response times. Higher post-trip resistance (260 mOhms) may impact thermal performance in rapid-cycling scenarios.

Higher Current Alternatives: MF-LS260, MF-LS300, MF-LS340

These parts are suitable for applications where the circuit can tolerate higher hold currents. MF-LS260 (2.6 A), MF-LS300 (3 A), and MF-LS340 (3.4 A) all maintain 24V ratings and -40°C to 85°C operating ranges. All three carry cURus and TUV certifications. These options are appropriate for circuits where the original 1.8 A hold current was conservative or where system redesign permits higher current thresholds. MF-LS340 offers the highest inventory availability (6495 pcs).

Regulatory Compliance:

All substitute parts are ROHS3 compliant and carry TUV certification. The LTP180LF's UL approval is not directly matched by the Bourns alternatives; however, cURus certification provides equivalent North American regulatory coverage. Applications requiring specific UL approval should confirm acceptance of cURus-certified alternatives with design authorities.

Frequently Asked Questions (FAQ)

Q: Can MF-LS100 be used as a direct replacement for LTP180LF?

A: MF-LS100 is electrically compatible at the 24V rating and operating temperature range. However, the 1 A hold current is significantly lower than the LTP180LF's 1.8 A specification. Use MF-LS100 only if circuit analysis confirms that 1 A protection is acceptable. The 7 s time-to-trip is substantially longer than the original 2.9 s, which may affect circuit protection response in fault conditions.

Q: What is the difference between MF-LS190 and LTP180LF in practical application?

A: The MF-LS190 holds current at 1.9 A versus 1.8 A, a 5.6% difference within typical component tolerance. Trip current increases from 3.8 A to 4.2 A. Time-to-trip improves from 2.9 s to 3 s. Post-trip resistance decreases from 120 mOhms to 100 mOhms, providing faster thermal recovery. These differences are negligible for most 24V circuit protection applications.

Q: Are all substitute parts available in the same strap package?

A: Yes, all substitute parts use strap package configuration. Physical dimensions vary: MF-LS100 measures 22.00mm × 5.05mm, while MF-LS340 measures 25.00mm × 15.35mm. Verify PCB layout compatibility before substitution, particularly for space-constrained designs.

Q: Do the Bourns Multifuse parts carry the same certifications as the Littelfuse PolySwitch?

A: The LTP180LF carries CSA, TUV, and UL approvals. Bourns MF-LS series parts carry cURus and TUV certifications. cURus certification provides equivalent regulatory coverage for North American applications. Applications requiring specific UL approval should confirm acceptance of cURus alternatives with relevant design authorities or regulatory bodies.

Q: Which substitute part should be selected for new designs?

A: MF-LS190 is the recommended choice for new designs due to closest electrical equivalence to LTP180LF, active production status, and adequate inventory. MF-LS340 offers superior inventory availability (6495 pcs) if circuit requirements permit the higher 3.4 A hold current rating.

Q: What is the moisture sensitivity level difference between LTP180LF and substitute parts?

A: LTP180LF carries MSL 2A (4 weeks); all Bourns MF-LS substitutes carry MSL 1 (Unlimited). This indicates Bourns parts have superior moisture resistance and do not require time-limited storage conditions.

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