SST 1 Equivalent & Substitute Parts Reference

Part Overview

The SST 1 is a 1 A, 125 V AC/DC surface mount board mount fuse manufactured by Bel Fuse Inc. in a 2-SMD, Square End Block package. This part is classified as Obsolete, which necessitates identification of active equivalent and substitute components for ongoing design support and procurement continuity. The SST 1 maintains ROHS3 compliance and operates across the -55°C to 125°C temperature range with slow blow response characteristics.

Key Parameters

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

Substitute Part Grouping Explanation

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

Primary Substitution Criteria:

Current Rating: 1 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Surface Mount (exact match required)
Package / Case: 2-SMD, Square End Block (exact match required)
Physical Dimensions: 0.240" L x 0.100" W x 0.100" H (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

Substitute Categories:

Direct Substitutes (Bel Fuse 0680L Series): Parts 0680L1000-01, 0680L1000-05, 0680L1000-11, 0680L1000-15, and 0680L1000-21 meet all primary substitution criteria. These parts are Active status and available in Tape & Reel packaging. Differences exist in Breaking Capacity (50A AC, 100A DC versus 50A), Melting I²t (1.5 versus 1.2), and DC Cold Resistance (0.175 Ohms versus 0.162 Ohms), but these variations remain within acceptable substitution parameters for the specified electrical and mechanical requirements.

Parametric Equivalents (Bel Fuse 0680H Series): Parts 0680H1000-01 and 0680H1000-05 satisfy all primary substitution criteria but exhibit different Breaking Capacity (100A AC, 500A DC), Melting I²t (0.79), and DC Cold Resistance (0.33 Ohms). These differences reflect a faster response characteristic and are classified as parametric equivalents rather than direct substitutes.

Cross-Manufacturer Substitutes (Littelfuse NANO²® Series): Parts 0449001.MR and 0452001.MRL from Littelfuse Inc. meet all primary substitution criteria. Physical dimensions vary slightly (0.106" W x 0.106" H versus 0.100" W x 0.100" H), and electrical characteristics differ (Melting I²t values of 1.76 and 1.98 respectively, DC Cold Resistance of 0.2516 and 0.225 Ohms). These parts are Active status with different approval agency certifications.

Parameter Comparison

Part Number	Manufacturer	Status	Current (A)	Voltage AC (V)	Voltage DC (V)	Response	Breaking Capacity	Melting I²t	DC Cold Resistance (Ω)	Packaging
SST 1	Bel Fuse Inc.	Obsolete	1	125	125	Slow Blow	50A	1.2	0.162	Cut Tape (CT) & Digi-Reel®
0680L1000-01	Bel Fuse	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680L1000-05	Bel Fuse Inc.	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680L1000-11	Bel Fuse Inc.	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680L1000-15	Bel Fuse	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680L1000-21	Bel Fuse Inc.	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680L1000-25	Bel Fuse Inc.	Active	1	125	125	Slow Blow	50A AC, 100A DC	1.5	0.175	Tape & Reel (TR)
0680H1000-01	Bel Fuse Inc.	Active	1	125	125	Slow Blow	100A AC, 500A DC	0.79	0.33	Tape & Reel (TR)
0680H1000-05	Bel Fuse Inc.	Active	1	125	125	Slow Blow	100A AC, 500A DC	0.79	0.33	Tape & Reel (TR)
0449001.MR	Littelfuse Inc.	Active	1	125	125	Slow Blow	50A	1.76	0.2516	Tape & Reel (TR)
0452001.MRL	Littelfuse Inc.	Active	1	125	125	Slow Blow	50A	1.98	0.225	Cut Tape (CT) & Digi-Reel®

Engineering Selection Recommendations

For Direct Replacement with Active Status: The Bel Fuse 0680L series (0680L1000-01, 0680L1000-05, 0680L1000-11, 0680L1000-15, 0680L1000-21, 0680L1000-25) provides the most direct substitution path. All parts maintain Active product status, ROHS3 compliance, and identical electrical and mechanical specifications to the SST 1. These parts are available in Tape & Reel packaging and carry AEC-Q200 and CE certifications. The 0680L1000-05 offers the highest inventory availability (52,236 pcs).

For Enhanced Breaking Capacity Requirements: The Bel Fuse 0680H series (0680H1000-01, 0680H1000-05) provides parametric equivalence with elevated Breaking Capacity ratings (100A AC, 500A DC) and faster response characteristics (Melting I²t of 0.79). These parts are suitable for applications requiring higher fault current withstand capability. Certification is limited to cURus. The 0680H1000-05 provides higher inventory (5,730 pcs).

For Cross-Manufacturer Substitution: Littelfuse NANO²® series parts 0449001.MR and 0452001.MRL satisfy all primary electrical and mechanical substitution criteria. The 0452001.MRL is available in Cut Tape & Digi-Reel packaging, matching the original SST 1 packaging format, with significantly higher inventory (221,172 pcs). Certifications differ from the original part, with CSA, PSE, and UR approvals for 0452001.MRL.

Frequently Asked Questions (FAQ)

Q: Can the 0680L1000 series directly replace the SST 1 in existing designs? A: Yes. The 0680L1000 series maintains identical current rating (1 A), voltage ratings (125 V AC/DC), response time (Slow Blow), mounting type (Surface Mount), package type (2-SMD, Square End Block), and physical dimensions (0.240" L x 0.100" W x 0.100" H). All parts are ROHS3 compliant and operate across -55°C to 125°C.

Q: What is the difference between the 0680L and 0680H series? A: The primary differences are Breaking Capacity and Melting I²t. The 0680L series provides 50A AC and 100A DC Breaking Capacity with Melting I²t of 1.5. The 0680H series provides 100A AC and 500A DC Breaking Capacity with Melting I²t of 0.79, indicating faster response. Both series meet all primary electrical and mechanical substitution criteria.

Q: Are Littelfuse NANO²® parts compatible with the SST 1 footprint? A: The Littelfuse parts 0449001.MR and 0452001.MRL meet all primary electrical and mechanical criteria. However, physical dimensions vary slightly: 0.240" L x 0.106" W x 0.106" H versus the SST 1 dimension of 0.240" L x 0.100" W x 0.100" H. PCB layout verification is required to confirm footprint compatibility.

Q: What packaging options are available for substitutes? A: The Bel Fuse 0680L and 0680H series are supplied in Tape & Reel (TR) packaging. The Littelfuse 0452001.MRL is available in Cut Tape (CT) & Digi-Reel® packaging, matching the original SST 1 packaging format. The Littelfuse 0449001.MR is supplied in Tape & Reel (TR) packaging.

Q: Which substitute part has the highest inventory availability? A: The Littelfuse 0452001.MRL offers the highest inventory with 221,172 pcs in stock. Among Bel Fuse alternatives, the 0680L1000-05 provides 52,236 pcs.

Q: Do all substitute parts maintain ROHS3 compliance? A: Yes. All listed substitute parts are ROHS3 compliant. The SST 1 original part is also ROHS3 compliant.

Q: What certifications should I verify for my application? A: The SST 1 carries AEC-Q200, CE, CSA, and cULus certifications. The 0680L series carries AEC-Q200, CE, and cURus certifications. The 0680H series carries only cURus certification. The Littelfuse 0449001.MR carries cULus and PSE certifications. The Littelfuse 0452001.MRL carries CSA, PSE, and UR certifications. Application-specific certification requirements must be verified against these listings.

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