SRP120SF Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The SRP120SF is an active polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® SRP series. This component provides overcurrent protection with a 15V maximum voltage rating and 1.2A hold current specification. The device is designed for user-defined strap mounting applications and operates across a temperature range of -40°C to 85°C. Identifying equivalent substitute parts is necessary to ensure supply chain flexibility, manage inventory optimization, and maintain design continuity when primary component availability is constrained.

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)
Type	Polymeric
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the SRP120SF are qualified based on strict parametric equivalence across all critical electrical and mechanical specifications. The substitution logic is determined by the following key parameters:

Voltage rating must equal 15V maximum
Current hold (Ih) specification must equal 1.2A maximum
Current trip (It) specification must equal 2.7A
Maximum current capacity must equal 100A
Time to trip must equal 5 seconds
Initial resistance (Ri) minimum must equal 85 mOhms
Post-trip resistance (R1) maximum must equal 220 mOhms
Operating temperature range must span -40°C to 85°C
Package type must be strap configuration
Physical dimensions must match 21.00mm L x 5.05mm W x 1.00mm thickness
Polymeric type classification must be maintained
RoHS3 compliance must be present

All substitute parts listed below meet these exact specifications and are therefore direct functional equivalents suitable for circuit design applications requiring the SRP120SF electrical and mechanical characteristics.

Parameter Comparison

Parameter	SRP120SF (Littelfuse)	0ZSA0120FF1E (Bel Fuse)	MF-S120 (Bourns)
Voltage - Max	15V	15V	15V
Current - Hold (Ih) (Max)	1.2 A	1.2 A	1.2 A
Current - Trip (It)	2.7 A	2.7 A	2.7 A
Current - Max	100 A	100 A	100 A
Time to Trip	5 s	5 s	5 s
Resistance - Initial (Ri) (Min)	85 mOhms	85 mOhms	85 mOhms
Resistance - Post Trip (R1) (Max)	220 mOhms	220 mOhms	220 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	Strap	Strap	Strap
Size / Dimension	21.00mm L x 5.05mm W	21.00mm L x 5.05mm W	21.00mm L x 5.05mm W
Thickness (Max)	1.00mm	1.00mm	1.00mm
Type	Polymeric	Polymeric	Polymeric
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active

Engineering Selection Recommendations

All three components listed—SRP120SF (Littelfuse Inc.), 0ZSA0120FF1E (Bel Fuse Inc.), and MF-S120 (Bourns Inc.)—maintain active product status and full ROHS3 compliance. Selection among these equivalents may be based on supply chain availability, inventory levels, and approval agency certifications specific to your application requirements. The SRP120SF carries CSA, TUV, and UL approvals. The 0ZSA0120FF1E carries cURus and TUV approvals with REACH Unaffected status. The MF-S120 carries cURus and TUV approvals with REACH Unaffected status. All three components are functionally interchangeable within circuits designed for the specified electrical and mechanical parameters.

Frequently Asked Questions (FAQ)

Q: Can the 0ZSA0120FF1E or MF-S120 be used as direct replacements for the SRP120SF in existing designs?

A: Yes. All three components share identical electrical specifications (15V, 1.2A hold current, 2.7A trip current, 5-second trip time) and mechanical dimensions (21.00mm x 5.05mm x 1.00mm strap package). They are parametric equivalents suitable for direct substitution in circuit applications.

Q: Are there differences in approval certifications between these parts?

A: The SRP120SF carries CSA, TUV, and UL certifications. The 0ZSA0120FF1E and MF-S120 both carry cURus and TUV certifications. Verify that the certification requirements of your specific application are met by the substitute part selected.

Q: What is the significance of the strap package type?

A: The strap package indicates a user-defined mounting configuration with lead spacing designed for direct circuit board integration. All three parts use identical strap packaging and physical dimensions, ensuring mechanical compatibility in PCB layouts.

Q: Do all substitute parts meet RoHS3 compliance?

A: Yes. The SRP120SF, 0ZSA0120FF1E, and MF-S120 are all ROHS3 compliant, meeting environmental and material restriction requirements for electronic component manufacturing.

Q: What parameters must remain constant when selecting a substitute?

A: Voltage rating (15V), current hold specification (1.2A), current trip specification (2.7A), operating temperature range (-40°C to 85°C), and physical dimensions (21.00mm x 5.05mm x 1.00mm) must all remain constant. Any deviation from these parameters indicates a non-equivalent component.

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