SSQ 2.5 Equivalent & Substitute Parts

Part Overview

The SSQ 2.5 is a 2.5 A surface mount board mount fuse rated for 125 V AC/DC operation, manufactured by Bel Fuse Inc. in a 2-SMD square end block package. This part is classified as obsolete, making equivalent and substitute components necessary for ongoing design support and production continuity. Substitute parts maintain the same electrical ratings and mechanical form factor while offering active product status from alternative manufacturers.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Surface Mount
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

Substitute parts for the SSQ 2.5 are classified into two categories based on electrical compatibility:

Direct Substitutes (Identical Electrical Ratings): Parts maintaining 2.5 A current rating with 125 V AC and 125 V DC voltage ratings qualify as direct substitutes. These include the 0679L2500-01 (Bel Fuse Inc.), 045102.5MRL, 045102.5MRSN, and 045302.5MR (Littelfuse Inc.), and 3404.0013.11 (SCHURTER Inc.). All maintain fast blow response time, surface mount configuration, and 2-SMD square end block package geometry.

Voltage-Enhanced Substitutes (Higher AC Rating): The 047602.5MR and 047602.5MRSN (Littelfuse Inc., NANO²® 476 series) provide 2.5 A current rating with 250 V AC and 125 V DC ratings. These parts are suitable for applications where the SSQ 2.5 is used in 125 V AC/DC circuits, as the higher AC voltage rating provides additional design margin without affecting circuit operation at the original voltage specification.

All substitute parts maintain the same current rating, DC voltage rating, fast blow response, surface mount technology, and operating temperature range as the original SSQ 2.5.

Parameter Comparison

Part Number	Manufacturer	Current Rating (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Package	Size (mm)	DC Cold Resistance (Ω)	Melting I²t	Product Status
SSQ 2.5	Bel Fuse Inc.	2.5	125	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.54 x 2.54	0.031	1.7	Obsolete
0679L2500-01	Bel Fuse Inc.	2.5	125	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.54 x 2.79	0.032	1.13	Active
047602.5MR	Littelfuse Inc.	2.5	250	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.69 x 2.69	0.0363	0.91	Active
047602.5MRSN	Littelfuse Inc.	2.5	250	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.69 x 2.69	0.0363	0.91	Active
045102.5MRL	Littelfuse Inc.	2.5	125	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.69 x 2.69	0.0286	1.029	Active
045102.5MRSN	Littelfuse Inc.	2.5	125	—	Fast Blow	2-SMD, Square End Block	6.10 x 2.69 x 2.69	0.0286	1.029	Active
045302.5MR	Littelfuse Inc.	2.5	125	125	Fast Blow	2-SMD, Square End Block	6.10 x 2.69 x 2.69	0.0286	1.029	Active
3404.0013.11	SCHURTER Inc.	2.5	125	125	Fast Blow	2-SMD, J-Lead	7.40 x 3.10 x 2.60	—	0.97	Active

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Specifications): The 045102.5MRL and 045302.5MR from Littelfuse Inc. are recommended as primary substitutes for the obsolete SSQ 2.5. Both maintain 2.5 A at 125 V AC/DC with fast blow response and 2-SMD square end block packaging. These parts carry active product status with established supply availability and hold CSA, PSE, and UL certifications.

For Enhanced Voltage Margin Applications: The 047602.5MR and 047602.5MRSN (Littelfuse NANO²® 476 series) provide 250 V AC rating while maintaining 2.5 A and 125 V DC operation. These are suitable for circuits originally designed for the SSQ 2.5 where additional AC voltage headroom is beneficial. Both parts are active with cURus certification.

For Bel Fuse Inc. Continuity: The 0679L2500-01 maintains manufacturer continuity from Bel Fuse Inc. with identical electrical ratings and active product status. This part carries AEC-Q200 and cURus certifications, suitable for automotive and industrial applications.

Package Consideration: The 3404.0013.11 from SCHURTER Inc. uses a 2-SMD J-Lead package rather than square end block. This part is suitable only if PCB layout accommodates J-Lead termination geometry (7.40 x 3.10 x 2.60 mm versus 6.10 x 2.69 x 2.69 mm for Littelfuse alternatives).

Frequently Asked Questions (FAQ)

Q: Can the 047602.5MR replace the SSQ 2.5 in a 125 V AC circuit? A: Yes. The 047602.5MR is rated for 250 V AC and 125 V DC, making it suitable for circuits operating at 125 V AC. The higher AC voltage rating does not affect operation at lower voltages.

Q: What is the difference between 045102.5MRL and 045102.5MRSN? A: Both are Littelfuse NANO²® 451 series parts with identical current rating, AC voltage, response time, and package. The 045102.5MRSN does not specify a DC voltage rating in the provided data, while 045102.5MRL is rated for 125 V DC. For applications requiring DC operation, 045102.5MRL is the appropriate selection.

Q: Is the 3404.0013.11 a direct replacement? A: The 3404.0013.11 maintains identical electrical ratings (2.5 A, 125 V AC/DC, fast blow) but uses a 2-SMD J-Lead package instead of square end block. PCB layout compatibility must be verified before selection.

Q: What certifications apply to substitute parts? A: Littelfuse NANO²® 451 and 453 series parts carry CSA, PSE, and UL certifications. Littelfuse NANO²® 476 series parts carry cURus certification. Bel Fuse 0679L2500-01 carries AEC-Q200 and cURus certifications. SCHURTER 3404.0013.11 carries cURus certification. Select based on application certification requirements.

Q: Are all substitute parts RoHS3 compliant? A: Yes. All substitute parts listed are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching the original SSQ 2.5 specifications.

Q: What is the difference in melting I²t values? A: Melting I²t indicates thermal energy required to melt the fuse element. Lower values indicate faster thermal response. The SSQ 2.5 has I²t of 1.7, while Littelfuse alternatives range from 0.91 to 1.029. These differences reflect design variations between manufacturers but do not affect substitution suitability for 2.5 A fast blow applications at rated voltage.

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