SRP120 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The SRP120 is a polymeric PTC resettable fuse manufactured by Littelfuse, rated for 15V maximum voltage and 1.2A hold current. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The SRP120 belongs to the PolySwitch® SRP series and is designed for applications requiring automatic overcurrent protection with resettable functionality.

Key Parameters

Parameter	Value
Voltage - Max	15V
Current - Hold (Ih) (Max)	1.2 A
Current - Trip (It)	2.7 A
Current - Max	100 A
Time to Trip	5 s
Resistance - Initial (Ri) (Min)	85 mOhms
Resistance - Post Trip (R1) (Max)	220 mOhms
Operating Temperature	-40°C ~ 85°C
Package / Case	Strap
Size / Dimension	0.827" L x 0.199" W (21.00mm x 5.05mm)
Thickness (Max)	0.039" (1.00mm)
Approval Agency	CSA, TUV, UL

Substitute Part Grouping Explanation

Substitution for the SRP120 is determined by matching the following critical parameters:

Voltage - Max: 15V
Current - Hold (Ih) (Max): 1.2 A
Current - Trip (It): 2.7 A
Resistance - Initial (Ri) (Min): 85 mOhms
Resistance - Post Trip (R1) (Max): 220 mOhms
Operating Temperature: -40°C ~ 85°C
Package / Case: Strap
Size / Dimension: 0.827" L x 0.199" W (21.00mm x 5.05mm)
Thickness (Max): 0.039" (1.00mm)

All identified substitute parts maintain identical electrical and mechanical specifications across these parameters, ensuring functional equivalence in circuit applications.

Parameter Comparison

Parameter	SRP120	SRP120F	SRP120SF	MF-S120
Manufacturer	Littelfuse	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.
Series	PolySwitch®, SRP	PolySwitch®, SRP	PolySwitch®, SRP	Multifuse®, MF-S
Product Status	Obsolete	Active	Active	Active
Voltage - Max	15V	15V	15V	15V
Current - Hold (Ih) (Max)	1.2 A	1.2 A	1.2 A	1.2 A
Current - Trip (It)	2.7 A	2.7 A	2.7 A	2.7 A
Current - Max	100 A	100 A	100 A	100 A
Time to Trip	5 s	5 s	5 s	5 s
Resistance - Initial (Ri) (Min)	85 mOhms	85 mOhms	85 mOhms	85 mOhms
Resistance - Post Trip (R1) (Max)	220 mOhms	220 mOhms	220 mOhms	220 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	Strap	Strap	Strap	Strap
Size / Dimension	0.827" L x 0.199" W (21.00mm x 5.05mm)	0.827" L x 0.199" W (21.00mm x 5.05mm)	0.827" L x 0.199" W (21.00mm x 5.05mm)	0.827" L x 0.199" W (21.00mm x 5.05mm)
Thickness (Max)	0.039" (1.00mm)	0.039" (1.00mm)	0.039" (1.00mm)	0.039" (1.00mm)
Approval Agency	CSA, TUV, UL	CSA, TUV, UL	CSA, TUV, UL	cURus, TUV
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	2A (4 Weeks)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

SRP120F and SRP120SF are parametric equivalents manufactured by Littelfuse, maintaining the same PolySwitch® SRP series designation. Both parts are active products with improved compliance status. SRP120F is available in bulk packaging, while SRP120SF offers higher inventory availability. Both achieve ROHS3 compliance and superior moisture sensitivity ratings compared to the obsolete SRP120.

MF-S120, manufactured by Bourns Inc., is a cross-manufacturer equivalent from the Multifuse® MF-S series. This part maintains identical electrical and mechanical specifications and is actively produced. The MF-S120 carries cURus and TUV certifications and achieves ROHS3 compliance.

For new designs and ongoing procurement, SRP120F, SRP120SF, or MF-S120 are suitable replacements for the obsolete SRP120, with selection based on packaging requirements, inventory availability, and certification preferences.

Frequently Asked Questions (FAQ)

Q: Can SRP120F directly replace SRP120 in existing designs?

A: Yes. SRP120F maintains identical electrical parameters (15V, 1.2A hold current, 2.7A trip current) and mechanical dimensions (21.00mm x 5.05mm strap package). The primary difference is product status (active vs. obsolete) and improved RoHS compliance.

Q: What is the difference between SRP120F and SRP120SF?

A: Both are Littelfuse PolySwitch® SRP series parts with identical electrical and mechanical specifications. The primary distinction is packaging format and inventory availability. SRP120F is supplied in bulk packaging with 3,777 units in stock, while SRP120SF has higher inventory (45,200 units) with unspecified packaging.

Q: Is MF-S120 compatible with SRP120 applications?

A: Yes. MF-S120 is a cross-manufacturer equivalent manufactured by Bourns Inc. It matches all critical electrical parameters (15V, 1.2A hold current, 2.7A trip current, 85 mOhms initial resistance, 220 mOhms post-trip resistance) and mechanical dimensions. The strap package and thermal operating range (-40°C to 85°C) are identical.

Q: What certifications apply to substitute parts?

A: SRP120F and SRP120SF carry CSA, TUV, and UL approvals. MF-S120 carries cURus and TUV approvals. All three substitute parts achieve ROHS3 compliance, whereas the original SRP120 is RoHS non-compliant.

Q: Are there packaging differences between substitute parts?

A: All substitute parts use the same strap package format with identical dimensions (0.827" L x 0.199" W, 21.00mm x 5.05mm). SRP120F is supplied in bulk packaging. SRP120SF packaging format is not specified. MF-S120 is supplied in bulk packaging.

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