SMD125-2 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The SMD125-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc., rated for 15V maximum voltage and 1.25A hold current. This component is classified as Obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The SMD125-2 operates across a temperature range of -40°C to 85°C and is housed in a 2920 (7351 Metric) surface mount package. Substitute parts must maintain electrical compatibility while meeting current design and compliance requirements.

Substiute Parts

SMD125-2

Littelfuse Inc.In Stock: 2891SMD125-2 Datasheet

Current PartRFQ

SMD125F-2

Littelfuse Inc.In Stock: 7378SMD125F-2 Datasheet

DirectRFQ

MF-SM125-2

Bourns Inc.In Stock: 5414MF-SM125-2 Datasheet

DirectRFQ

0ZCF0125FF2C

Bel Fuse Inc.In Stock: 21920ZCF0125FF2C Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict alignment with the following electrical and mechanical parameters:

Critical Parameters for Substitution:

• Voltage - Max: Must equal or exceed 15V
• Current - Hold (Ih) (Max): Must equal 1.25 A
• Current - Trip (It): Must equal 2.5 A
• Resistance - Initial (Ri) (Min): Must equal 70 mOhms
• Operating Temperature: Must support -40°C ~ 85°C range
• Mounting Type: Must be Surface Mount
• Package / Case: Must be compatible with 2920 (7351 Metric) or equivalent 2-SMD footprint
• Type: Must be Polymeric PTC

Substitute Parts Identified:

Group 1 - Direct Electrical & Mechanical Equivalents (Active Status):

• SMD125F-2 (Littelfuse Inc.): Identical electrical specifications, 2-SMD package variant, Active product status
• MF-SM125-2 (Bourns Inc.): Identical hold and trip currents, 2-SMD package, Active product status, enhanced current rating (100A max vs 40A)

Group 2 - Voltage-Enhanced Substitute (Active Status):

• 0ZCF0125FF2C (Bel Fuse Inc.): Identical hold and trip currents, elevated voltage rating (33V vs 15V), 2920 (7351 Metric) package, Active product status

Parameter Comparison

Engineering Selection Recommendations

SMD125F-2 (Littelfuse Inc.) is the primary direct substitute. It maintains identical electrical specifications and package dimensions while offering Active product status and ROHS3 compliance. This part is the preferred choice for direct replacement in existing designs.

MF-SM125-2 (Bourns Inc.) provides equivalent electrical performance with enhanced current rating capability (100A max). It includes AEC-Q200 automotive qualification and superior moisture sensitivity rating (MSL 1). This part is suitable for applications requiring automotive-grade reliability or extended shelf life without moisture control.

0ZCF0125FF2C (Bel Fuse Inc.) offers elevated voltage rating (33V) while maintaining identical hold and trip current specifications. This part is appropriate for designs operating at higher system voltages or where voltage margin is required. It includes AEC-Q200 qualification and is housed in the original 2920 (7351 Metric) package format.

All substitute parts are Active products with ROHS3 compliance, addressing the obsolescence and regulatory status of the original SMD125-2.

Frequently Asked Questions (FAQ)

Q: Can SMD125F-2 be used as a direct replacement for SMD125-2?

A: Yes. SMD125F-2 maintains identical electrical specifications (15V, 1.25A hold, 2.5A trip) and package dimensions (0.290" L x 0.202" W). The primary difference is packaging format (2-SMD vs 2920 Metric designation) and product status (Active vs Obsolete). Both are Littelfuse PolySwitch products with equivalent performance.

Q: What is the difference between the 2-SMD and 2920 (7351 Metric) package designations?

A: Both designations refer to the same physical footprint and dimensions (0.290" L x 0.202" W, 7.36mm x 5.12mm). The 2-SMD designation is a generic surface mount descriptor, while 2920 (7351 Metric) is the specific IPC metric package code. These are mechanically and electrically interchangeable on PCB layouts.

Q: Why does 0ZCF0125FF2C have a higher voltage rating (33V) than the original SMD125-2 (15V)?

A: The 0ZCF0125FF2C is designed for higher system voltage applications. The elevated voltage rating does not affect hold current (1.25A) or trip current (2.5A) specifications. This part is suitable for circuits operating above 15V where voltage margin is required.

Q: Is MF-SM125-2 suitable for automotive applications?

A: Yes. MF-SM125-2 carries AEC-Q200 automotive qualification and cURus/TUV approvals. It is rated for automotive-grade reliability and includes MSL 1 (Unlimited) moisture sensitivity, providing superior environmental performance compared to the original SMD125-2.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. SMD125F-2, MF-SM125-2, and 0ZCF0125FF2C are all ROHS3 compliant. The original SMD125-2 is RoHS non-compliant, making these substitutes necessary for designs requiring regulatory compliance.

Q: What is the difference in initial resistance between these parts?

A: SMD125-2, SMD125F-2, and MF-SM125-2 specify 70 mOhms minimum initial resistance. The 0ZCF0125FF2C specifies 50 mOhms minimum, which is lower and provides reduced voltage drop during normal operation. This difference is negligible for most applications but may be relevant in low-voltage, high-current circuits.