SST 5 Surface Mount Board Mount Fuse 5A 125VAC/VDC Equivalent & Substitute Parts

Part Overview

The SST 5 is a 5A 125VAC/VDC surface mount board mount fuse manufactured by Bel Fuse Inc. in 2-SMD square end block package configuration. This part is classified as obsolete, though functionally equivalent active alternatives are available from both Bel Fuse and Littelfuse product lines. Identifying suitable substitutes is necessary due to the obsolete status of the original SST 5 series, ensuring continued design support and supply chain continuity for applications requiring 5A slow blow fuse protection at 125V AC/DC ratings.

Key Parameters

Parameter	Value
Current Rating	5 A
Voltage Rating AC	125 V
Voltage Rating DC	125 V
Response Time	Slow Blow
Mounting Type	Surface Mount
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	2-SMD, Square End Block
Operating Temperature Range	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility for the SST 5 is determined by strict equivalence across the following critical parameters: current rating (5A), voltage ratings (125V AC and 125V DC), response time (slow blow), mounting type (surface mount), fuse type (board mount, cartridge style excluded), and package configuration (2-SMD square end block). All substitute parts listed maintain these core electrical and mechanical specifications.

Substitute parts are grouped into two categories:

Direct Manufacturer Substitutes (Bel Fuse 0680L Series): Parts 0680L5000-01, 0680L5000-05, 0680L5000-11, 0680L5000-15, 0680L5000-21, and 0680L5000-25 are active products from Bel Fuse with identical electrical ratings and package dimensions. These differ only in packaging format (tape & reel or cut tape) and internal manufacturing specifications (melting I²t: 37 versus 38).

Parametric Equivalents (Bel Fuse 0680H Series): Parts 0680H5000-01 and 0680H5000-05 maintain identical electrical ratings and package dimensions but feature enhanced breaking capacity (100A AC, 500A DC versus 50A AC) and lower melting I²t (24 versus 37-38). These are functionally compatible for applications where higher breaking capacity is acceptable.

Cross-Manufacturer Alternatives (Littelfuse NANO²® Series): Parts 0449005.MR and 0452005.MRL from Littelfuse maintain the required 5A, 125V AC/DC ratings and slow blow response in 2-SMD square end block packages. Dimensional variations exist (0.106" width and height versus 0.100"), and melting I²t values differ (59.59 and 53.72 respectively).

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Breaking Capacity AC (A)	Breaking Capacity DC (A)	Melting I²t	DC Cold Resistance (Ω)	Package	Size L×W×H (mm)	Product Status
SST 5	Bel Fuse Inc.	SST	5	125	125	Slow Blow	50	—	38	0.017	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Obsolete
0680L5000-01	Bel Fuse	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680L5000-05	Bel Fuse Inc.	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680L5000-11	Bel Fuse	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680L5000-15	Bel Fuse	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680L5000-21	Bel Fuse	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680L5000-25	Bel Fuse Inc.	0680L	5	125	125	Slow Blow	50	100	37	0.019	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680H5000-01	Bel Fuse Inc.	0680H	5	125	125	Slow Blow	100	500	24	0.026	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0680H5000-05	Bel Fuse Inc.	0680H	5	125	125	Slow Blow	100	500	24	0.026	2-SMD, Square End Block	6.10 × 2.54 × 2.54	Active
0449005.MR	Littelfuse	NANO²® 449	5	125	125	Slow Blow	50	—	59.59	0.0171	2-SMD, Square End Block	6.10 × 2.69 × 2.69	Active
0452005.MRL	Littelfuse Inc.	NANO²® 452	5	125	125	Slow Blow	50	—	53.72	0.0136	2-SMD, Square End Block	6.10 × 2.69 × 2.69	Active

Engineering Selection Recommendations

Primary Recommendation: The Bel Fuse 0680L series (0680L5000-01, 0680L5000-05, 0680L5000-11, 0680L5000-15, 0680L5000-21, 0680L5000-25) represents the most direct substitution path. These parts maintain identical package dimensions, electrical ratings, and are active products with established supply availability. Selection among these variants depends on packaging requirements: tape & reel (TR) formats for automated assembly or cut tape (CT) & Digi-Reel® for manual placement. All variants carry AEC-Q200 and CE certifications matching or exceeding the original SST 5 compliance profile.

Secondary Recommendation: The Bel Fuse 0680H series (0680H5000-01, 0680H5000-05) provides parametric equivalence with enhanced breaking capacity specifications (100A AC, 500A DC). These are suitable for applications where higher fault current withstand capability is beneficial. Note that cURus certification is provided; AEC-Q200 and CE certifications are not listed for this series.

Cross-Manufacturer Alternative: Littelfuse NANO²® parts (0449005.MR, 0452005.MRL) maintain the required 5A, 125V AC/DC electrical specifications and slow blow response. Dimensional differences exist in width and height (2.69mm versus 2.54mm), requiring PCB layout verification. Melting I²t values are higher (53.72–59.59 versus 37–38), indicating different thermal response characteristics. These parts carry cULus and PSE certifications; CSA and UR certifications vary by part number.

Frequently Asked Questions (FAQ)

Q: Can the 0680L series directly replace the obsolete SST 5?

A: Yes. The 0680L series maintains identical current rating (5A), voltage ratings (125V AC/DC), response time (slow blow), mounting type (surface mount), and package configuration (2-SMD square end block). Package dimensions are identical at 6.10mm × 2.54mm × 2.54mm. Selection depends on packaging format preference (tape & reel or cut tape).

Q: What is the difference between 0680L and 0680H series?

A: Both series maintain identical electrical ratings (5A, 125V AC/DC, slow blow). The 0680H series features higher breaking capacity (100A AC, 500A DC versus 50A AC, 100A DC) and lower melting I²t (24 versus 37). The 0680H is suitable for applications requiring enhanced fault current protection. Certification profiles differ; verify compliance requirements for your application.

Q: Are Littelfuse NANO²® parts compatible with the SST 5 footprint?

A: Electrical compatibility is confirmed (5A, 125V AC/DC, slow blow). However, dimensional differences exist: NANO²® parts measure 6.10mm × 2.69mm × 2.69mm versus the SST 5 at 6.10mm × 2.54mm × 2.54mm. PCB layout and land pattern verification is required before design implementation. Melting I²t characteristics also differ (53.72–59.59 versus 38), affecting thermal response.

Q: Which packaging format should I select from the 0680L series?

A: Tape & reel (TR) packaging is standard for high-volume automated assembly processes. Cut tape (CT) & Digi-Reel® packaging is suitable for lower-volume production or manual placement. Electrical and mechanical specifications are identical across packaging variants; selection is driven by manufacturing process requirements.

Q: What certifications apply to each substitute part?

A: Bel Fuse 0680L series carries AEC-Q200, CE, and cURus certifications. Bel Fuse 0680H series carries cURus certification only. Littelfuse 0449005.MR carries cULus and PSE certifications. Littelfuse 0452005.MRL carries CSA, PSE, and UR certifications. Verify that selected part certifications meet your application and regional compliance requirements.

Q: Can I use the 0680H series as a drop-in replacement?

A: Electrical and mechanical compatibility is confirmed. The 0680H provides enhanced breaking capacity and different thermal characteristics (lower melting I²t). Applications requiring the original SST 5 specifications can use 0680H without functional degradation. Verify that higher breaking capacity and different thermal response do not conflict with circuit protection strategy.

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