SRP175 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The SRP175 is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 15V maximum voltage and 1.75A hold current. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The SRP175 belongs to the PolySwitch® SRP series and is designed for applications requiring automatic overcurrent protection with user-defined strap mounting.

Key Parameters

Parameter	Value
Voltage - Max	15V
Current - Hold (Ih) (Max)	1.75 A
Current - Trip (It)	3.8 A
Current - Max	100 A
Resistance - Initial (Ri) (Min)	50 mOhms
Resistance - Post Trip (R1) (Max)	120 mOhms
Operating Temperature	-40°C ~ 85°C
Package / Case	Strap
Size / Dimension	0.866" L x 0.199" W (22.00mm x 5.05mm)
Thickness (Max)	0.039" (1.00mm)
Approval Agency	CSA, TUV, UL

Substitute Part Grouping Explanation

Substitution eligibility for the SRP175 is determined by strict equivalence across the following critical parameters:

Voltage - Max: 15V
Current - Hold (Ih) (Max): 1.75 A
Current - Trip (It): 3.8 A
Resistance - Initial (Ri) (Min): 50 mOhms
Resistance - Post Trip (R1) (Max): 120 mOhms
Operating Temperature: -40°C ~ 85°C
Package / Case: Strap
Approval Agency: CSA, TUV, UL (or equivalent regional certifications)

All identified substitute parts meet these core electrical and mechanical parameters. Variations in packaging format, product status, and compliance certifications are noted but do not affect functional interchangeability within the specified parameter range.

Parameter Comparison

Parameter	SRP175	SRP175F	SRP175SF	MF-S175	0ZSA0175FF1E
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.	Bel Fuse Inc.
Series	PolySwitch® SRP	PolySwitch® SRP	PolySwitch® SRP	Multifuse® MF-S	0ZSA
Product Status	Obsolete	Active	Active	Active	Active
Voltage - Max	15V	15V	15V	15V	15V
Current - Hold (Ih) (Max)	1.75 A	1.75 A	1.75 A	1.75 A	1.75 A
Current - Trip (It)	3.8 A	3.8 A	3.8 A	3.8 A	3.8 A
Current - Max	100 A	100 A	100 A	100 A	100 A
Resistance - Initial (Ri) (Min)	50 mOhms	50 mOhms	50 mOhms	50 mOhms	50 mOhms
Resistance - Post Trip (R1) (Max)	120 mOhms	120 mOhms	120 mOhms	120 mOhms	120 mOhms
Operating Temperature	-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
Size / Dimension	0.866" L x 0.199" W (22.00mm x 5.05mm)	0.866" L x 0.199" W (22.00mm x 5.05mm)	0.866" L x 0.199" W (22.00mm x 5.05mm)	0.827" L x 0.199" W (21.00mm x 5.05mm)	0.866" L x 0.199" W (22.00mm x 5.05mm)
Thickness (Max)	0.039" (1.00mm)	0.039" (1.00mm)	0.039" (1.00mm)	0.039" (1.00mm)	0.039" (1.00mm)
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CSA, TUV, UL	CSA, TUV, UL	CSA, TUV, UL	cURus, TUV	cURus, TUV

Engineering Selection Recommendations

All substitute parts listed maintain electrical and mechanical equivalence to the SRP175 across critical parameters. Selection should be based on the following factors:

Littelfuse PolySwitch® SRP Series (SRP175F, SRP175SF): These parts provide direct manufacturer continuity with active product status and ROHS3 compliance. SRP175F is available in bulk packaging with improved moisture sensitivity rating (MSL 1, Unlimited). SRP175SF offers the highest inventory availability and maintains identical electrical specifications.

Bourns Multifuse® MF-S175: This cross-manufacturer substitute provides active product status and ROHS3 compliance. Physical dimensions vary slightly (0.827" L vs. 0.866" L), and time-to-trip specification is 4 seconds versus 5 seconds. Approval agencies include cURus and TUV.

Bel Fuse 0ZSA0175FF1E: This parametric equivalent maintains all critical electrical specifications and offers active product status with ROHS3 compliance. Physical dimensions and time-to-trip match the SRP175 specification. Approval agencies include cURus and TUV.

For applications requiring strict regulatory compliance with current standards, SRP175F and SRP175SF are preferred due to ROHS3 compliance and CSA/TUV/UL certifications. For cross-manufacturer sourcing flexibility, MF-S175 and 0ZSA0175FF1E provide functionally equivalent alternatives.

Frequently Asked Questions (FAQ)

Q: Can SRP175F directly replace the obsolete SRP175?

A: Yes. SRP175F maintains identical electrical parameters (15V, 1.75A hold current, 3.8A trip current, 50 mOhms initial resistance, 120 mOhms post-trip resistance) and mechanical form factor. The primary difference is active product status and improved RoHS compliance (ROHS3 vs. non-compliant).

Q: What is the difference between SRP175F and SRP175SF?

A: Both are Littelfuse PolySwitch® SRP series parts with identical electrical and mechanical specifications. SRP175F is available in bulk packaging with MSL 1 (Unlimited) moisture sensitivity. SRP175SF offers higher inventory availability. Selection depends on packaging requirements and supply chain needs.

Q: Can MF-S175 be used as a substitute for SRP175?

A: Yes, with dimensional consideration. MF-S175 meets all critical electrical parameters but has a slightly shorter length (0.827" vs. 0.866"). Time-to-trip is 4 seconds versus 5 seconds for the SRP175. Physical space constraints in the application must be evaluated.

Q: Are there approval agency differences between substitutes?

A: The SRP175, SRP175F, and SRP175SF carry CSA, TUV, and UL approvals. MF-S175 and 0ZSA0175FF1E carry cURus and TUV approvals. Applications requiring specific agency certification should confirm compatibility with design requirements.

Q: What is the significance of RoHS compliance differences?

A: The original SRP175 is RoHS non-compliant. All substitute parts (SRP175F, SRP175SF, MF-S175, 0ZSA0175FF1E) are ROHS3 compliant, meeting current environmental and regulatory standards for new designs and procurement.

Q: How do moisture sensitivity levels affect part selection?

A: SRP175 carries MSL 2A (4 Weeks). SRP175F, SRP175SF, MF-S175, and 0ZSA0175FF1E all carry MSL 1 (Unlimited), indicating superior moisture resistance and extended shelf life without special storage requirements.

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