SMD300-2 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The SMD300-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc. as part of the PolySwitch® SMD series. This component is rated for 6V maximum voltage with a 3A hold current (Ih) and is designed for surface mount applications in the 2920 (7351 Metric) package format. The SMD300-2 is currently listed as obsolete, making identification of compatible substitute parts essential for ongoing production and maintenance applications.

Substiute Parts

SMD300-2

Littelfuse Inc.In Stock: 3358SMD300-2 Datasheet

Current PartRFQ

SMD300F-2

Littelfuse Inc.In Stock: 17153SMD300F-2 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SMD300-2 is determined by strict equivalence across the following critical parameters:

Voltage Rating: Maximum voltage must be 6V or greater to maintain circuit protection integrity.

Current Characteristics: Hold current (Ih) must be 3A maximum, trip current (It) must be 6A, and maximum current must be 40A to ensure identical protection behavior.

Thermal Performance: Operating temperature range must span -40°C to 85°C to support the same environmental conditions.

Electrical Characteristics: Initial resistance (Ri) minimum of 15 mOhms and post-trip resistance (R1) maximum of 48 mOhms must be maintained for consistent circuit performance.

Trip Time: Time to trip must be 35 seconds to preserve protection response timing.

Mechanical Compatibility: Surface mount mounting type with 2920 (7351 Metric) package dimensions (0.290" L x 0.202" W, 3.00mm maximum thickness) ensures PCB layout compatibility.

Certifications: Parts must carry CSA, TUV, and UL approvals for regulatory compliance.

The SMD300F-2 meets all these criteria and is classified as a direct substitute.

Parameter Comparison

Engineering Selection Recommendations

The SMD300F-2 is the direct substitute for the obsolete SMD300-2. Both components are manufactured by Littelfuse Inc. within the PolySwitch® SMD series and share identical electrical and thermal specifications across all critical parameters.

The SMD300F-2 offers two significant advantages over the main part:

Product Status: The SMD300F-2 is listed as Active, ensuring continued availability and supply chain reliability, whereas the SMD300-2 is obsolete.

Regulatory Compliance: The SMD300F-2 is ROHS3 Compliant, representing an upgrade from the RoHS non-compliant status of the SMD300-2. This compliance status is relevant for applications subject to RoHS regulations.

Both parts carry identical certifications from CSA, TUV, and UL, maintaining regulatory approval requirements. The physical dimensions, electrical characteristics, and operating parameters are fully equivalent, ensuring direct PCB-level compatibility without design modifications.

Frequently Asked Questions (FAQ)

Q: Can SMD300F-2 be used as a direct replacement for SMD300-2 on existing PCBs?

A: Yes. The SMD300F-2 is electrically and mechanically equivalent to the SMD300-2. Both components have identical dimensions (0.290" L x 0.202" W, 3.00mm thickness), identical electrical ratings (6V, 3A hold current, 6A trip current), and identical operating temperature ranges (-40°C to 85°C). No PCB layout modifications are required.

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

A: Both designations refer to the same physical package format used for surface mount polymeric PTC resettable fuses. The 2920 designation uses imperial measurements (0.290" x 0.202"), while 2-SMD is an alternative industry designation for the same component footprint. The physical dimensions and mounting characteristics are identical.

Q: Why is the SMD300-2 listed as obsolete?

A: The SMD300-2 has been superseded by the SMD300F-2 in Littelfuse's product portfolio. The SMD300F-2 offers the same electrical and thermal performance with the added benefit of ROHS3 compliance and active product status, ensuring ongoing availability and support.

Q: Are there any compliance differences between SMD300-2 and SMD300F-2?

A: Both parts carry identical certifications from CSA, TUV, and UL. The primary compliance difference is that SMD300F-2 is ROHS3 Compliant, while SMD300-2 is RoHS non-compliant. Both parts maintain REACH Unaffected status and share the same ECCN (EAR99) and HTSUS (8533.40.8070) classifications.

Q: What is the moisture sensitivity level for these components?

A: Both the SMD300-2 and SMD300F-2 have a Moisture Sensitivity Level (MSL) of 2A, which allows for 4 weeks of floor life under controlled conditions before baking is required.

Q: Can these components be used interchangeably in new designs?

A: Yes. For new designs, the SMD300F-2 is the recommended choice due to its active product status, ROHS3 compliance, and assured long-term availability. The electrical and mechanical specifications are identical to the SMD300-2, making it suitable for all applications where the SMD300-2 was originally specified.