SST 750 Equivalent & Substitute Parts

Part Overview

The SST 750 is a 750 mA surface mount board mount fuse rated for 125 V AC and 125 V DC operation with slow blow response characteristics. Manufactured by Bel Fuse Inc., this component is classified as obsolete. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary to maintain design continuity and ensure ongoing component availability for new production and field replacements.

Key Parameters

Parameter	Value
Manufacturer Part Number	SST 750
Manufacturer	Bel Fuse Inc.
Current Rating	750 mA
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
Size / Dimension	0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm)
Operating Temperature	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the SST 750 is determined by strict equivalence across the following critical parameters:

Current Rating: 750 mA (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)
Size / Dimension: 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 parts are grouped into two categories:

Direct Substitutes (Bel Fuse Inc. 0680L Series): Parts 0680L0750-01, 0680L0750-05, 0680L0750-11, 0680L0750-15, 0680L0750-21, and 0680L0750-25 are direct functional equivalents with identical electrical and mechanical specifications. These parts are active products with enhanced breaking capacity ratings and are available in Tape & Reel packaging.

Parametric Equivalents (Bel Fuse Inc. 0680H Series): Parts 0680H0750-01 and 0680H0750-05 meet all critical electrical and mechanical parameters but feature higher breaking capacity ratings (100A AC, 500A DC versus 50A AC, 100A DC) and lower melting I²t values (0.28 versus 0.62). These represent faster response characteristics within the same slow blow category.

Cross-Manufacturer Equivalent (Littelfuse Inc. NANO²® Series): Part 0449.750MR and related variants (0452.750MRL, 0454.750MR, 0454.750NR) meet all critical electrical and mechanical parameters with minor dimensional variations in width and height (0.106" versus 0.100"). These are active products from an alternative manufacturer.

Parameter Comparison

Part Number	Manufacturer	Current Rating (mA)	Voltage AC (V)	Voltage DC (V)	Response Time	Breaking Capacity AC (A)	Breaking Capacity DC (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	Packaging
SST 750	Bel Fuse Inc.	750	125	125	Slow Blow	50	—	0.66	0.25	Obsolete	Cut Tape (CT) & Digi-Reel®
0680L0750-01	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680L0750-05	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680L0750-11	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680L0750-15	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680L0750-21	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680L0750-25	Bel Fuse Inc.	750	125	125	Slow Blow	50	100	0.62	0.33	Active	Tape & Reel (TR)
0680H0750-01	Bel Fuse Inc.	750	125	125	Slow Blow	100	500	0.28	0.53	Active	Tape & Reel (TR)
0680H0750-05	Bel Fuse Inc.	750	125	125	Slow Blow	100	500	0.28	0.53	Active	Tape & Reel (TR)
0449.750MR	Littelfuse Inc.	750	125	125	Slow Blow	50	—	0.847	0.408	Active	Tape & Reel (TR)
0452.750MRL	Littelfuse Inc.	750	125	125	Slow Blow	50	—	0.904	0.36	Active	Tape & Reel (TR)

Engineering Selection Recommendations

For Direct Replacement with Active Product Status:

The 0680L series (0680L0750-01, 0680L0750-05, 0680L0750-11, 0680L0750-15, 0680L0750-21, 0680L0750-25) represents the primary substitution path. All variants are active products from Bel Fuse Inc. with identical electrical specifications to the SST 750. These parts carry AEC-Q200 and CE certifications and are ROHS3 compliant. The 0680L series offers improved DC breaking capacity (100A DC) compared to the SST 750 specification, providing enhanced performance margin. Packaging is standardized as Tape & Reel, suitable for automated assembly processes.

For Enhanced Breaking Capacity Requirements:

The 0680H series (0680H0750-01, 0680H0750-05) provides significantly higher breaking capacity ratings (100A AC, 500A DC) with lower melting I²t values (0.28), indicating faster response characteristics. These parts are suitable for applications requiring higher fault current handling. Certification is limited to cURus. DC cold resistance is elevated at 0.53 Ohms compared to 0.25 Ohms in the SST 750.

For Cross-Manufacturer Sourcing:

The Littelfuse NANO²® 0449.750MR and 0452.750MRL variants provide functional equivalence with minor dimensional variations (0.106" width and height versus 0.100"). These parts are active products with ROHS3 compliance. The 0449.750MR carries cULus certification, while 0452.750MRL carries CSA and UR certifications. Melting I²t values are higher (0.847 and 0.904 respectively), indicating slower response characteristics within the slow blow category.

Frequently Asked Questions (FAQ)

Q: Can the 0680L series parts be used as direct replacements for SST 750?

A: Yes. The 0680L series maintains identical current rating (750 mA), voltage ratings (125 V AC/DC), response time (slow blow), mounting type (surface mount), and package dimensions (0.240" L x 0.100" W x 0.100" H). All variants are active products with enhanced DC breaking capacity and are ROHS3 compliant.

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

A: Both series meet the SST 750 electrical specifications. The 0680H series features higher breaking capacity (100A AC, 500A DC versus 50A AC, 100A DC) and lower melting I²t (0.28 versus 0.62), indicating faster response. The 0680H series is suitable for applications requiring enhanced fault current handling.

Q: Are Littelfuse NANO²® parts compatible with SST 750 footprints?

A: The Littelfuse 0449.750MR and 0452.750MRL have minor dimensional variations in width and height (0.106" versus 0.100"). While functionally equivalent in electrical performance, PCB footprint compatibility must be verified for the specific application.

Q: What certifications apply to substitute parts?

A: The 0680L series carries AEC-Q200, CE, and cURus certifications. The 0680H series carries cURus certification. The Littelfuse 0449.750MR carries cULus certification, while 0452.750MRL carries CSA and UR certifications. All substitute parts are ROHS3 compliant.

Q: Why is the SST 750 obsolete?

A: The SST 750 has been discontinued by Bel Fuse Inc. The 0680L series represents the active product line replacement with equivalent functionality and improved specifications.

Q: Can packaging format affect substitution?

A: Yes. The SST 750 is available in Cut Tape (CT) and Digi-Reel® packaging. All substitute parts are supplied in Tape & Reel (TR) format, which is standard for automated assembly. Verify that your assembly process supports Tape & Reel packaging.

Q: What is the significance of melting I²t values in fuse selection?

A: Melting I²t indicates the thermal energy required to melt the fuse element. Lower values indicate faster response to overcurrent conditions. The SST 750 has a melting I²t of 0.66. The 0680L series (0.62) and 0680H series (0.28) represent comparable or faster response characteristics.

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