Equivalent & Substitute Parts for MF-SM100/33-2-99

Part Overview

The MF-SM100/33-2-99 is a Polymeric PTC Resettable Fuse manufactured by Bourns Inc. in the Multifuse® MF-SM series. This component is rated for 33V maximum voltage with a 1.1A hold current and 2.2A trip current, designed for surface mount applications in 2-SMD package configuration. The part is currently listed as Obsolete, making identification of equivalent and substitute components necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Voltage - Max	33V
Current - Hold (Ih) (Max)	1.1 A
Current - Trip (It)	2.2 A
Current - Max	40 A
Time to Trip	500 ms
Resistance - Initial (Ri) (Min)	120 mOhms
Resistance - Post Trip (R1) (Max)	410 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	2-SMD
Type	Polymeric

Substitute Part Grouping Explanation

Substitute parts for the MF-SM100/33-2-99 are identified based on strict electrical and mechanical parameter matching. The following criteria determine substitution eligibility:

Critical Matching Parameters:

Voltage - Max: 33V
Current - Hold (Ih) (Max): 1.1 A
Current - Trip (It): 2.2 A
Current - Max: 40 A
Time to Trip: 500 ms
Resistance - Initial (Ri) (Min): 120 mOhms
Resistance - Post Trip (R1) (Max): 410 mOhms
Operating Temperature: -40°C ~ 85°C
Mounting Type: Surface Mount
Package / Case: 2-SMD
Type: Polymeric

All identified substitutes meet these electrical specifications and physical package requirements, enabling direct functional replacement in circuit applications.

Parameter Comparison

Parameter	MF-SM100/33-2-99 (Main)	MF-SM100/33-2 (Bourns)	SMD100F/33-2 (Littelfuse)
Manufacturer	Bourns Inc.	Bourns Inc.	Littelfuse Inc.
Series	Multifuse®, MF-SM	Multifuse®, MF-SM	PolySwitch®, SMD
Product Status	Obsolete	Active	Active
Voltage - Max	33V	33V	33V
Current - Hold (Ih) (Max)	1.1 A	1.1 A	1.1 A
Current - Trip (It)	2.2 A	2.2 A	2.2 A
Current - Max	40 A	40 A	40 A
Time to Trip	500 ms	500 ms	500 ms
Resistance - Initial (Ri) (Min)	120 mOhms	120 mOhms	120 mOhms
Resistance - Post Trip (R1) (Max)	410 mOhms	410 mOhms	410 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Package / Case	2-SMD	2-SMD	2-SMD
Type	Polymeric	Polymeric	Polymeric
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	cURus, TUV	cURus, TUV	CSA, TUV, UL
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	2A (4 Weeks)
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected
Size / Dimension	0.287" L x 0.214" W (7.31mm x 5.44mm)	0.287" L x 0.214" W (7.31mm x 5.44mm)	0.290" L x 0.202" W (7.36mm x 5.12mm)
Thickness (Max)	0.118" (3.00mm)	0.118" (3.00mm)	0.118" (3.00mm)

Engineering Selection Recommendations

MF-SM100/33-2 (Bourns Inc.): This part is the direct parametric equivalent from the same manufacturer and series. Product status is Active, ensuring ongoing availability and supply chain stability. Compliance certifications (cURus, TUV) and RoHS3 status match the original specification. Moisture Sensitivity Level of 1 (Unlimited) provides the same handling requirements as the obsolete part. This substitute is the primary recommendation for direct replacement.

SMD100F/33-2 (Littelfuse Inc.): This part meets all critical electrical and mechanical parameters. Product status is Active with higher inventory availability (39,400 pcs). Compliance certifications include CSA, TUV, and UL approvals. The primary difference is Moisture Sensitivity Level of 2A (4 Weeks), requiring controlled storage conditions. Physical dimensions show minor variations (0.290" L x 0.202" W versus 0.287" L x 0.214" W), remaining within 2-SMD package classification. This substitute is suitable for applications where MSL 2A handling procedures are acceptable.

Frequently Asked Questions (FAQ)

Q: Can MF-SM100/33-2 directly replace MF-SM100/33-2-99?

A: Yes. Both parts share identical electrical specifications (33V, 1.1A hold current, 2.2A trip current, 500ms trip time, 120mOhms initial resistance, 410mOhms post-trip resistance) and physical package (2-SMD, 0.287" L x 0.214" W). The primary difference is product status: MF-SM100/33-2 is Active while MF-SM100/33-2-99 is Obsolete. Compliance certifications and RoHS status are equivalent.

Q: What are the differences between the Bourns and Littelfuse substitutes?

A: Both meet identical electrical specifications and 2-SMD package requirements. Key differences are: (1) Manufacturer: Bourns versus Littelfuse; (2) Series designation: Multifuse® MF-SM versus PolySwitch® SMD; (3) Approval agencies: cURus/TUV versus CSA/TUV/UL; (4) Moisture Sensitivity Level: 1 (Unlimited) versus 2A (4 Weeks); (5) Physical dimensions: 0.287" L x 0.214" W versus 0.290" L x 0.202" W. All differences remain within acceptable substitution parameters.

Q: Does Moisture Sensitivity Level 2A affect component selection?

A: Moisture Sensitivity Level 2A (4 Weeks) for SMD100F/33-2 requires controlled storage and handling procedures. Components must be stored in dry conditions and used within 4 weeks of package opening. If unlimited moisture exposure is required, MF-SM100/33-2 with MSL 1 is the appropriate choice.

Q: Are physical dimension variations significant?

A: Physical dimensions for SMD100F/33-2 (0.290" L x 0.202" W) differ slightly from MF-SM100/33-2-99 (0.287" L x 0.214" W). Both remain within 2-SMD package classification with identical 0.118" (3.00mm) maximum thickness. Variations are within typical component tolerance ranges and do not affect PCB footprint compatibility for standard 2-SMD layouts.

Q: Which substitute offers the best supply chain availability?

A: SMD100F/33-2 (Littelfuse) shows the highest inventory level at 39,400 pcs. MF-SM100/33-2 (Bourns) provides 2,200 pcs. Both parts are Active status, ensuring continued manufacturing and supply. Selection should prioritize application requirements and compliance certifications over inventory levels alone.

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