SST 500/5K Equivalent & Substitute Parts Reference

Part Overview

The SST 500/5K is a 500 mA surface mount board mount fuse manufactured by Bel Fuse Inc., rated for 125 V AC and 125 V DC operation with slow blow response characteristics. This part is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and ongoing production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives within the same application category.

Key Parameters

Parameter	Value
Current Rating	500 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
Moisture Sensitivity Level	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict adherence to the following parameters:

Primary Substitution Criteria:

Current Rating: 500 mA (exact match required)
Voltage Rating AC: 125 V (exact match required)
Voltage Rating DC: 125 V (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)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

Secondary Compatibility Parameters:

Size / Dimension: 0.240" L x 0.100" W x 0.100" H (6.10mm x 2.54mm x 2.54mm) for direct mechanical fit
RoHS Status: ROHS3 Compliant (environmental compliance)
Moisture Sensitivity Level: 1 (Unlimited) (handling and storage compatibility)

Substitute parts are classified into two categories: Direct Manufacturer Parts (same series, different packaging or tape configuration) and Parametric Equivalents (different manufacturer or series with identical electrical and mechanical specifications).

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating	Voltage AC	Voltage DC	Response Time	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance (Ohms)	Product Status	Packaging
SST 500/5K	Bel Fuse Inc.	SST	500 mA	125 V	125 V	Slow Blow	50A	0.27	0.49	Obsolete	Cut Tape (CT) & Digi-Reel®
0680L0500-01	Bel Fuse Inc.	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680L0500-05	Bel Fuse Inc.	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680L0500-11	Bel Fuse	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680L0500-15	Bel Fuse Inc.	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680L0500-21	Bel Fuse	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680L0500-25	Bel Fuse	0680L	500 mA	125 V	125 V	Slow Blow	50A AC, 100A DC	0.27	0.58	Active	Tape & Reel (TR)
0680H0500-01	Bel Fuse Inc.	0680H	500 mA	125 V	125 V	Slow Blow	100A AC, 500A DC	0.13	1.1	Active	Tape & Reel (TR)
0680H0500-05	Bel Fuse Inc.	0680H	500 mA	125 V	125 V	Slow Blow	100A AC, 500A DC	0.13	1.1	Active	Tape & Reel (TR)
0449.500MR	Littelfuse Inc.	NANO²® 449	500 mA	125 V	125 V	Slow Blow	50A	0.258	0.7633	Active	Tape & Reel (TR)
0452.500MRL	Littelfuse Inc.	NANO²® 452	500 mA	125 V	125 V	Slow Blow	50A	0.24	0.7	Active	Cut Tape (CT) & Digi-Reel®

Engineering Selection Recommendations

Direct Manufacturer Substitutes (Bel Fuse Inc. 0680L Series):

The 0680L0500 series parts (0680L0500-01, 0680L0500-05, 0680L0500-11, 0680L0500-15, 0680L0500-21, 0680L0500-25) are active direct substitutes for the obsolete SST 500/5K. These parts maintain identical electrical specifications and mechanical dimensions. The primary difference is packaging configuration (Tape & Reel versus Cut Tape & Digi-Reel). All 0680L variants carry AEC-Q200 and CE certifications matching the original part's compliance profile. Selection among 0680L variants depends on procurement packaging requirements and inventory availability.

Parametric Equivalents (Bel Fuse Inc. 0680H Series):

The 0680H0500 series (0680H0500-01, 0680H0500-05) provides parametric equivalence with enhanced breaking capacity specifications (100A AC, 500A DC versus 50A AC). These parts are suitable for applications requiring higher fault current withstanding capability while maintaining identical current rating, voltage rating, and response time. The 0680H series carries cURus certification. DC cold resistance is higher (1.1 Ohms versus 0.49 Ohms for SST 500/5K), and melting I²t is lower (0.13 versus 0.27), indicating faster thermal response.

Cross-Manufacturer Alternatives (Littelfuse Inc.):

The Littelfuse NANO²® 449 (0449.500MR) and NANO²® 452 (0452.500MRL) series provide functional equivalence with identical current, voltage, and response time specifications. These parts maintain the same 2-SMD square end block package and operating temperature range. The 0449.500MR carries cULus certification, while 0452.500MRL carries CSA and UR certifications. Mechanical dimensions show minor variations (0.106" width and height versus 0.100" for SST 500/5K), requiring PCB layout verification for direct substitution.

Frequently Asked Questions (FAQ)

Q: Can 0680L0500 series parts directly replace the obsolete SST 500/5K?

A: Yes. The 0680L0500 series maintains identical electrical specifications (500 mA, 125 V AC/DC, slow blow response) and mechanical dimensions (0.240" L x 0.100" W x 0.100" H). The primary difference is packaging format (Tape & Reel versus Cut Tape & Digi-Reel). All variants are active products with current manufacturing status.

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

A: Both series maintain identical current rating (500 mA), voltage rating (125 V AC/DC), and response time (slow blow). The 0680H series provides higher breaking capacity (100A AC, 500A DC versus 50A AC, 100A DC for 0680L) and lower melting I²t (0.13 versus 0.27). DC cold resistance is higher in 0680H (1.1 Ohms versus 0.58 Ohms). Selection depends on fault current withstanding requirements.

Q: Are Littelfuse NANO²® parts mechanically compatible with the SST 500/5K footprint?

A: The NANO²® 449 and 452 series maintain the same 0.240" length and 2-SMD square end block package. However, width and height dimensions are 0.106" versus 0.100" for the original part. PCB layout verification is required to confirm mechanical fit within the existing footprint.

Q: Which substitute part has the highest inventory availability?

A: The Littelfuse 0452.500MRL (NANO²® 452) has the highest inventory at 150,200 pieces. Among Bel Fuse parts, 0680L0500-05 has 33,063 pieces in stock.

Q: What certifications apply to substitute parts?

A: Bel Fuse 0680L series carries AEC-Q200, CE, and cURus certifications. Bel Fuse 0680H series carries cURus certification. Littelfuse 0449.500MR carries cULus certification. Littelfuse 0452.500MRL carries CSA and UR certifications. Verify certification requirements for your specific application before selection.

Q: Can packaging variants (CT vs. TR) be used interchangeably in production?

A: Packaging variants differ in tape configuration and reel format but contain identical components. Interchangeability depends on assembly equipment compatibility. Cut Tape (CT) & Digi-Reel® packaging differs from standard Tape & Reel (TR) format. Confirm equipment specifications before switching packaging types.

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