Equivalent & Substitute Parts for MF-S350S

Part Overview

The MF-S350S is a polymeric PTC resettable fuse manufactured by Bourns Inc. in the Multifuse® MF-S series. This component provides overcurrent protection at 30V with a 4.6A hold current rating and is designed for strap mounting applications. The MF-S350S is classified as obsolete, making identification of equivalent and substitute parts essential for ongoing system support and component procurement.

Key Parameters

Parameter	Value
Voltage - Max	30V
Current - Hold (Ih) (Max)	4.6 A
Current - Trip (It)	6.3 A
Current - Max	100 A
Time to Trip	3 s
Resistance - Initial (Ri) (Min)	17 mOhms
Resistance - Post Trip (R1) (Max)	40 mOhms
Operating Temperature	-40°C ~ 85°C
Package / Case	Strap
Size / Dimension	1.185" L x 0.522" W (30.10mm x 13.25mm)
Thickness (Max)	0.043" (1.10mm)
Type	Polymeric
RoHS Status	ROHS3 Compliant
Approval Agency	cURus, TUV

Substitute Part Grouping Explanation

Substitution of polymeric PTC resettable fuses is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Parameters:

Maximum voltage rating must equal or exceed the application requirement (30V)
Hold current (Ih) must match the circuit design specification (4.6A)
Trip current (It) and time to trip define the protection response characteristics
Initial and post-trip resistance values affect circuit performance during normal and fault conditions

Mechanical Parameters:

Package type (strap mounting) must be identical
Physical dimensions must accommodate the PCB layout and connector interface
Thickness must not exceed the specified maximum (0.043")

Compliance Parameters:

RoHS3 compliance status
Regulatory approvals (cURus, TUV, CSA, UL)

Substitute parts are classified into two categories: direct equivalents (identical electrical and mechanical specifications) and similar alternatives (matching core electrical parameters with minor variations in secondary characteristics).

Parameter Comparison

Parameter	MF-S350S (Main)	MF-S350 (Direct)	SRP350F (Similar)	SRP420F (Similar)
Manufacturer	Bourns Inc.	Bourns Inc.	Littelfuse Inc.	Littelfuse
Series	Multifuse® MF-S	Multifuse® MF-S	PolySwitch® SRP	PolySwitch® SRP
Product Status	Obsolete	Active	Active	Active
Voltage - Max	30V	30V	30V	30V
Current - Hold (Ih) (Max)	4.6 A	4.6 A	4.6 A	4.2 A
Current - Trip (It)	6.3 A	6.3 A	6.3 A	7.6 A
Current - Max	100 A	100 A	100 A	100 A
Time to Trip	3 s	3 s	3 s	6 s
Resistance - Initial (Ri) (Min)	17 mOhms	17 mOhms	17 mOhms	12 mOhms
Resistance - Post Trip (R1) (Max)	40 mOhms	40 mOhms	50 mOhms	40 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	1.185" L x 0.522" W (30.10mm x 13.25mm)	1.185" L x 0.522" W (30.10mm x 13.25mm)	1.185" L x 0.522" W (30.10mm x 13.25mm)	1.240" L x 0.522" W (31.50mm x 13.25mm)
Thickness (Max)	0.043" (1.10mm)	0.043" (1.10mm)	0.043" (1.10mm)	0.043" (1.10mm)
Type	Polymeric	Polymeric	Polymeric	Polymeric
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	cURus, TUV	cURus, TUV	CSA, TUV, UL	CSA, TUV, UL

Engineering Selection Recommendations

MF-S350 (Direct Equivalent)

The MF-S350 is the direct equivalent to the obsolete MF-S350S. Both parts are manufactured by Bourns Inc. in the Multifuse® MF-S series and share identical electrical and mechanical specifications. The MF-S350 is currently in active production status with bulk packaging availability. This part provides a seamless replacement with no design modifications required. Regulatory approvals include cURus and TUV certification, with ROHS3 compliance.

SRP350F (Similar Alternative)

The SRP350F is manufactured by Littelfuse Inc. in the PolySwitch® SRP series and matches the MF-S350S across all critical electrical parameters: 30V maximum voltage, 4.6A hold current, 6.3A trip current, and 3-second trip time. Physical dimensions and thickness are identical. The primary difference is post-trip resistance, which reaches a maximum of 50 mOhms compared to 40 mOhms in the original part. This component is in active production with expanded regulatory approvals including CSA, TUV, and UL certification, plus ROHS3 compliance.

SRP420F (Similar Alternative with Current Rating Variation)

The SRP420F is manufactured by Littelfuse Inc. in the PolySwitch® SRP series and operates at 30V maximum voltage. This part differs from the MF-S350S in hold current (4.2A versus 4.6A), trip current (7.6A versus 6.3A), and time to trip (6 seconds versus 3 seconds). Initial resistance is lower at 12 mOhms minimum. Physical length is slightly greater at 1.240" (31.50mm) compared to 1.185" (30.10mm). This component is in active production with CSA, TUV, and UL certification, plus ROHS3 compliance. Selection of this part requires verification that the higher current ratings and extended trip time are compatible with the application circuit design.

Frequently Asked Questions (FAQ)

Q: Can MF-S350 be used as a direct replacement for MF-S350S?

A: Yes. The MF-S350 is a direct equivalent with identical electrical and mechanical specifications. No design modifications are required. The primary difference is product status: MF-S350S is obsolete while MF-S350 is in active production.

Q: What is the difference between MF-S350 and SRP350F?

A: Both parts share identical voltage (30V), hold current (4.6A), trip current (6.3A), and trip time (3 seconds) specifications. Physical dimensions and thickness are identical. The SRP350F has a maximum post-trip resistance of 50 mOhms compared to 40 mOhms for the MF-S350. The SRP350F is manufactured by Littelfuse and carries additional regulatory approvals (CSA, UL) beyond the cURus and TUV certifications of the Bourns part.

Q: When should SRP420F be considered as a substitute?

A: The SRP420F has a higher hold current rating (4.2A versus 4.6A) and extended trip time (6 seconds versus 3 seconds). This part is suitable only when the application circuit design can accommodate these higher current and time parameters. The slightly larger physical length (1.240" versus 1.185") must also be verified against PCB layout constraints.

Q: Are all substitute parts strap-mounted?

A: Yes. All parts listed—MF-S350S, MF-S350, SRP350F, and SRP420F—use strap mounting and are compatible with identical connector interfaces.

Q: What compliance certifications apply to these parts?

A: All parts are ROHS3 compliant. The MF-S350S and MF-S350 carry cURus and TUV approvals. The SRP350F and SRP420F carry CSA, TUV, and UL approvals, providing broader regulatory coverage.

Q: Does operating temperature range differ among the substitute parts?

A: No. All parts operate across the identical temperature range of -40°C to 85°C.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message