SST 375 Surface Mount Fuse – Equivalent & Substitute Parts

Part Overview

The SST 375 is a 375 mA, 125 V AC/DC surface mount board fuse manufactured by Bel Fuse Inc. in a 2-SMD, Square End Block package. This component is classified as obsolete, though 738 units remain in stock. Due to its obsolete status, active equivalent parts from both Bel Fuse and Littelfuse are available as direct functional replacements. Substitute parts maintain identical electrical ratings, mechanical dimensions, and thermal characteristics while offering improved availability through active product lines.

Key Parameters

Parameter	Value
Current Rating	375 mA
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Slow Blow
Package / Case	2-SMD, Square End Block
Mounting Type	Surface Mount
Operating Temperature Range	-55°C to 125°C
Size / Dimension	0.240" L × 0.100" W × 0.100" H (6.10mm × 2.54mm × 2.54mm)
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following parameters:

Current Rating: 375 mA (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 2-SMD, Square End Block (exact match required)
Mounting Type: Surface Mount (exact match required)
Operating Temperature Range: -55°C to 125°C (exact match required)
RoHS Status: ROHS3 Compliant (exact match required)
Moisture Sensitivity Level: 1 (Unlimited) (exact match required)

All substitute parts listed below meet these criteria. Variations in secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and approval agency certifications do not disqualify substitution but are documented for engineering reference.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating	Voltage AC/DC	Response Time	Package	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance (Ω)	Approval Agency	Product Status	Inventory
SST 375	Bel Fuse Inc.	SST	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A	0.15	0.72	AEC-Q200, CE, CSA, cULus	Obsolete	738 Pcs
0680L0375-01	Bel Fuse	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	2963 Pcs
0680L0375-05	Bel Fuse Inc.	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	22784 Pcs
0680L0375-11	Bel Fuse	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	664 Pcs
0680L0375-15	Bel Fuse Inc.	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	1134 Pcs
0680L0375-21	Bel Fuse	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	1011 Pcs
0680L0375-25	Bel Fuse	0680L	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A AC, 100A DC	0.14	0.93	AEC-Q200, CE, cURus	Active	829 Pcs
0449.375MR	Littelfuse	NANO²® 449	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A	0.088	1.513	cULus	Active	1872 Pcs
0452.375MRL	Littelfuse Inc.	NANO²® 452	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A	0.101	1.2	CSA, UR	Active	15400 Pcs
0452.375NRL	Littelfuse Inc.	NANO²® 452	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A	0.101	1.2	CSA, UR	Active	1863 Pcs
0454.375MR	Littelfuse	NANO²® 454	375 mA	125 V / 125 V	Slow Blow	2-SMD, Square End Block	50A	0.101	1.2	CSA, UR	Active	3642 Pcs

Engineering Selection Recommendations

Bel Fuse 0680L Series (0680L0375-01, 0680L0375-05, 0680L0375-11, 0680L0375-15, 0680L0375-21, 0680L0375-25)

These parts are direct successors to the SST 375 within the Bel Fuse product portfolio. All variants maintain identical electrical and mechanical specifications. The 0680L series is active and carries AEC-Q200 certification, suitable for automotive and high-reliability applications. Part 0680L0375-05 offers the highest inventory availability (22,784 units). Selection among 0680L variants should be based on packaging format requirements (Tape & Reel) and internal design revision needs.

Littelfuse NANO²® Series (0449.375MR, 0452.375MRL, 0452.375NRL, 0454.375MR)

These parts provide functional equivalence with different approval agency certifications. The NANO²® 452 variants (0452.375MRL and 0452.375NRL) offer the highest inventory (15,400 and 1,863 units respectively) and carry CSA and UR certifications. The NANO²® 449 (0449.375MR) carries cULus certification. The NANO²® 454 (0454.375MR) also carries CSA and UR certifications. Selection should prioritize application-specific certification requirements and supply chain availability.

Frequently Asked Questions (FAQ)

Q: Can I substitute SST 375 with any of the listed parts?

A: Yes. All listed parts meet the mandatory substitution criteria: 375 mA current rating, 125 V AC/DC voltage rating, slow blow response time, 2-SMD Square End Block package, surface mount configuration, -55°C to 125°C operating range, ROHS3 compliance, and MSL 1 rating. Electrical and mechanical compatibility is assured.

Q: What is the difference between Bel Fuse 0680L variants?

A: All 0680L variants (0680L0375-01, 0680L0375-05, 0680L0375-11, 0680L0375-15, 0680L0375-21, 0680L0375-25) are electrically and mechanically identical. Differences are internal design revisions or manufacturing date codes. Selection can be based on inventory availability or internal supply chain requirements.

Q: Why do Littelfuse NANO²® parts have different melting I²t and DC cold resistance values?

A: Littelfuse NANO²® series employ different internal fuse element designs compared to Bel Fuse SST and 0680L series, resulting in variations in melting I²t (0.088 to 0.101 versus 0.14 to 0.15) and DC cold resistance (1.2 to 1.513 Ω versus 0.72 to 0.93 Ω). Despite these secondary parameter differences, all parts maintain identical primary electrical ratings and response characteristics required for substitution.

Q: Which part should I select for new designs?

A: For new designs, select from active product lines: Bel Fuse 0680L series or Littelfuse NANO²® series. Both offer superior availability and ongoing manufacturer support compared to the obsolete SST 375. Selection should be based on certification requirements (AEC-Q200 for automotive, CSA/UR for other applications) and supply chain preferences.

Q: Are there any dimensional differences between substitute parts?

A: Bel Fuse SST 375 and 0680L series maintain identical dimensions: 0.240" L × 0.100" W × 0.100" H (6.10mm × 2.54mm × 2.54mm). Littelfuse NANO²® parts have slightly larger width and height: 0.240" L × 0.106" W × 0.106" H (6.10mm × 2.69mm × 2.69mm). Verify PCB footprint compatibility before substitution with NANO²® parts.

Q: What packaging formats are available?

A: SST 375 is supplied in Cut Tape (CT) and Digi-Reel® formats. All substitute parts are supplied in Tape & Reel (TR) format. Confirm packaging compatibility with assembly equipment and procurement requirements.

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