SSQ 400/5K Surface Mount Fuse - Equivalent & Substitute Parts

Part Overview

The SSQ 400/5K is a 400 mA surface mount board mount fuse rated for 125 V AC/DC operation, manufactured by Bel Fuse Inc. This component is classified as Not For New Designs, indicating it has been superseded in the manufacturer's product line. Finding equivalent substitute parts is necessary for legacy system maintenance, repair applications, and inventory replenishment where the original part number is unavailable or discontinued from active production.

Substiute Parts

SSQ 400/5K

Bel Fuse Inc.In Stock: 1002SSQ 400/5K Datasheet

Current PartRFQ

0679L0375-05

Bel Fuse Inc.In Stock: 52670679L0375-05 Datasheet

SimilarRFQ

0448.400MR

Littelfuse Inc.In Stock: 61620448.400MR Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the SSQ 400/5K are identified based on the following critical parameters that must align for functional equivalence:

• Current Rating: 400 mA (primary protection characteristic)
• Voltage Rating: 125 V AC and 125 V DC (system voltage compatibility)
• Response Time: Fast Blow (circuit protection speed requirement)
• Mounting Type: Surface Mount (PCB assembly compatibility)
• Fuse Type: Board Mount, Cartridge Style Excluded (form factor requirement)
• Package / Case: 2-SMD, Square End Block (footprint and land pattern compatibility)
• Operating Temperature Range: -55°C ~ 125°C (thermal environment compatibility)

Two substitute parts meet these criteria with allowable variations in physical dimensions and electrical characteristics within acceptable engineering tolerances for this product category.

Parameter Comparison

Engineering Selection Recommendations

0448.400MR (Littelfuse Inc. NANO²® 448 Series)

This substitute provides exact current rating matching at 400 mA and maintains all critical electrical parameters including voltage ratings, response time, and breaking capacity at rated voltage. The part is in Active product status with current manufacturing support. Approval agencies include CSA and UL certifications. Physical dimensions show minor variations (0.106" width and height versus 0.100") within acceptable PCB assembly tolerances for 2-SMD footprints. This part is the preferred direct replacement for new procurement and legacy system repairs.

0679L0375-05 (Bel Fuse Inc. 0679L Series)

This substitute is manufactured by the same original equipment manufacturer (Bel Fuse Inc.) and maintains identical voltage ratings and package form factor. The current rating is 375 mA, representing a 6.25% reduction from the 400 mA specification. This part is in Active product status with AEC-Q200 automotive qualification. Physical dimensions show a minor height variation (0.110" versus 0.100"). This substitute is suitable for applications where the 375 mA rating provides adequate circuit protection margin or where OEM continuity is required.

Frequently Asked Questions (FAQ)

Q: Can the 0679L0375-05 (375 mA) be used as a direct replacement for the SSQ 400/5K (400 mA)?

A: The 0679L0375-05 has a lower current rating (375 mA versus 400 mA). This substitute is suitable only if the circuit design accommodates the reduced current threshold. The 25 mA difference may affect circuit protection characteristics in applications with marginal current margins.

Q: Are there physical footprint compatibility concerns with the substitute parts?

A: All three parts share the same 2-SMD, Square End Block package designation and 6.10 mm length. Width and height variations are minor (0.100" to 0.106" range) and fall within standard PCB assembly tolerances for surface mount components. Existing PCB layouts designed for the SSQ 400/5K will accommodate both substitute parts without modification.

Q: What are the key differences in approval certifications between the main part and substitutes?

A: The SSQ 400/5K carries CE, CSA, and cULus approvals. The 0448.400MR carries CSA and UL approvals. The 0679L0375-05 carries AEC-Q200 and cURus approvals. All three parts meet industrial and consumer safety standards. Application-specific certification requirements should be verified against system-level compliance documentation.

Q: Why is the SSQ 400/5K marked as Not For New Designs?

A: This designation indicates the part has been superseded in the manufacturer's active product line. The 0679L0375-05 from the same manufacturer represents the current generation equivalent. For new system designs, the 0448.400MR or 0679L0375-05 are recommended for long-term supply chain stability.

Q: What is the significance of the DC Cold Resistance values listed for the substitute parts?

A: DC Cold Resistance (0.33 Ohms for 0679L0375-05 and 0.4895 Ohms for 0448.400MR) represents the fuse element resistance in the non-blown state. These values are provided for circuit analysis and thermal modeling. The variation between parts reflects different fuse element designs and does not affect functional substitution for standard circuit protection applications.