MF-SM250-2-99 Equivalent & Substitute Parts

Part Overview

The MF-SM250-2-99 is a Polymeric PTC Resettable Fuse manufactured by Bourns Inc. in the Multifuse® MF-SM series. This component is rated for 15V maximum voltage with a 2.5A hold current and 5A trip current in a 2-SMD surface mount package. The part is currently listed as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Voltage - Max	15V
Current - Hold (Ih) (Max)	2.5 A
Current - Trip (It)	5 A
Resistance - Initial (Ri) (Min)	24 mOhms
Resistance - Post Trip (R1) (Max)	85 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	2-SMD
Type	Polymeric

Substitute Part Grouping Explanation

Substitution for the MF-SM250-2-99 is determined by strict alignment of electrical and mechanical parameters. The primary substitution criteria are:

Parametric Equivalents (Direct Substitutes): Parts matching all critical electrical parameters (15V maximum voltage, 2.5A hold current, 5A trip current, 24 mOhms initial resistance, 85 mOhms post-trip resistance) and identical mounting configuration (Surface Mount 2-SMD package). These parts are functionally interchangeable with identical performance characteristics.

Direct Manufacturer Alternatives: Parts from different manufacturers with matching voltage, hold current, trip current, and package type, though minor variations in initial resistance or maximum current rating may exist.

Similar Parts (Different Mounting): Parts with matching voltage and hold current specifications but different mounting types (Strap configuration instead of Surface Mount). These require circuit board redesign and are suitable only when mounting flexibility exists.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Voltage - Max	Current - Hold (Ih) (Max)	Current - Trip (It)	Resistance - Initial (Ri) (Min)	Resistance - Post Trip (R1) (Max)	Mounting Type	Package / Case	Product Status
MF-SM250-2-99	Bourns Inc.	15V	2.5 A	5 A	24 mOhms	85 mOhms	Surface Mount	2-SMD	Obsolete
MF-SM250-2	Bourns Inc.	15V	2.5 A	5 A	24 mOhms	85 mOhms	Surface Mount	2-SMD	Active
MF-SM250-2-006	Bourns Inc.	15V	2.5 A	5 A	24 mOhms	85 mOhms	Surface Mount	2-SMD	Active
SMD250F-2	Littelfuse Inc.	15V	2.5 A	5 A	35 mOhms	85 mOhms	Surface Mount	2-SMD	Active
PFSM.250.2	SCHURTER Inc.	15V	2.5 A	5 A	24 mOhms	85 mOhms	Surface Mount	2-SMD	Active
LR4-190F	Littelfuse Inc.	15V	1.9 A	3.9 A	39 mOhms	102 mOhms	User Defined	Strap	Active
LR4-260SF	Littelfuse Inc.	15V	2.6 A	5.8 A	20 mOhms	63 mOhms	User Defined	Strap	Active
SRP120F	Littelfuse Inc.	15V	1.2 A	2.7 A	85 mOhms	220 mOhms	User Defined	Strap	Active
SRP120LF	Littelfuse Inc.	15V	1.2 A	2.7 A	85 mOhms	220 mOhms	User Defined	Strap	Active
SRP120SF	Littelfuse Inc.	15V	1.2 A	2.7 A	85 mOhms	220 mOhms	User Defined	Strap	Active

Engineering Selection Recommendations

Recommended Primary Substitutes (Parametric Equivalents):

MF-SM250-2 and MF-SM250-2-006 from Bourns Inc. are direct parametric equivalents with identical electrical specifications and Surface Mount 2-SMD packaging. Both parts are Active status and carry AEC-Q200 ratings with cURus and TUV approvals, matching the original part's compliance profile.

PFSM.250.2 from SCHURTER Inc. is a parametric equivalent with identical voltage, hold current, trip current, and resistance specifications. This part is Active status with AEC-Q200 rating and cURus/TUV approvals, providing full functional compatibility in Surface Mount 2-SMD configuration.

Alternative Substitute (Different Manufacturer, Same Package):

SMD250F-2 from Littelfuse Inc. (PolySwitch® SMD series) matches the voltage, hold current, and trip current specifications with Surface Mount 2-SMD packaging. Initial resistance is 35 mOhms versus 24 mOhms on the original part. This part is Active status with CSA, TUV, and UL approvals.

Similar Parts (Strap Configuration - Requires Design Modification):

LR4-190F, LR4-260SF, SRP120F, SRP120LF, and SRP120SF are Littelfuse PolySwitch® and SRP series parts with 15V rating but different mounting types (User Defined Strap). These parts have different hold current and trip current specifications and require circuit board redesign for implementation.

Frequently Asked Questions (FAQ)

Q: Can MF-SM250-2 directly replace MF-SM250-2-99 without design changes?

A: Yes. MF-SM250-2 is a parametric equivalent with identical electrical specifications (15V, 2.5A hold, 5A trip) and Surface Mount 2-SMD packaging. No circuit board modifications are required.

Q: What is the difference between MF-SM250-2 and PFSM.250.2?

A: Both are parametric equivalents with identical electrical parameters and Surface Mount 2-SMD packaging. The primary difference is manufacturer: Bourns Inc. versus SCHURTER Inc. Both are Active status with AEC-Q200 ratings and equivalent compliance certifications.

Q: Why is SMD250F-2 listed as a substitute if the initial resistance differs?

A: SMD250F-2 matches the critical functional parameters: 15V maximum voltage, 2.5A hold current, and 5A trip current in Surface Mount 2-SMD configuration. The initial resistance difference (35 mOhms versus 24 mOhms) falls within acceptable tolerance for polymeric PTC fuse operation and does not prevent functional substitution.

Q: Can strap-mounted parts like LR4-190F replace the surface mount MF-SM250-2-99?

A: No. Strap-mounted parts require different circuit board design and assembly methods. These parts are listed as similar alternatives only when circuit board redesign is feasible. Additionally, LR4-190F has lower hold current (1.9A versus 2.5A) and different trip characteristics.

Q: What compliance certifications should I verify when selecting a substitute?

A: The original MF-SM250-2-99 carries AEC-Q200 rating with cURus and TUV approvals. Recommended substitutes (MF-SM250-2, MF-SM250-2-006, PFSM.250.2) maintain these certifications. SMD250F-2 carries CSA, TUV, and UL approvals, providing equivalent regulatory coverage for most applications.

Q: Is moisture sensitivity level a factor in substitution?

A: The original part has MSL 1 (Unlimited). MF-SM250-2 and PFSM.250.2 maintain MSL 1. SMD250F-2 has MSL 2A (4 Weeks), requiring controlled storage conditions. This difference should be evaluated based on your supply chain and storage practices.

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