SSQ 2 Equivalent & Substitute Parts

Part Overview

The SSQ 2 is a 2 A, 125 V AC/DC surface mount board mount fuse manufactured by Bel Fuse Inc. in a 2-SMD, Square End Block package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The SSQ 2 operates across a temperature range of -55°C to 125°C with fast blow response characteristics and is RoHS3 compliant.

Key Parameters

Parameter	Value
Current Rating	2 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Surface Mount
Fuse Type	Board Mount (Cartridge Style Excluded)
Operating Temperature Range	-55°C to 125°C
Breaking Capacity (AC)	50 A
Breaking Capacity (DC)	300 A
RoHS Status	RoHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the SSQ 2 are grouped based on electrical and mechanical compatibility. The primary substitution criteria are:

Current rating of 2 A
Voltage ratings of 125 V AC and 125 V DC (or higher AC voltage with 125 V DC minimum)
Fast blow response time
Surface mount board mount configuration
Operating temperature range of -55°C to 125°C
RoHS3 compliance

Direct substitutes maintain identical electrical specifications and package dimensions. Similar substitutes meet the core electrical requirements but may differ in package case style (Square End Block versus J-Lead), melting I²t characteristics, or DC cold resistance within acceptable engineering tolerances. Parts with reduced current ratings (250 mA) or elevated AC voltage ratings (250 V AC) are listed for reference but require circuit validation before substitution.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage AC (V)	Voltage DC (V)	Response Time	Package Case	Melting I²t	DC Cold Resistance (Ω)	Product Status
SSQ 2	Bel Fuse Inc.	2	125	125	Fast Blow	2-SMD, Square End Block	1	0.039	Obsolete
0679L2000-01	Bel Fuse Inc.	2	125	125	Fast Blow	2-SMD, Square End Block	0.68	0.041	Active
0451002.MRL	Littelfuse Inc.	2	125	125	Fast Blow	2-SMD, Square End Block	0.53	0.0367	Active
0451002.MRSN	Littelfuse Inc.	2	125	125	Fast Blow	2-SMD, Square End Block	0.53	0.0367	Active
0453002.MR	Littelfuse Inc.	2	125	125	Fast Blow	2-SMD, Square End Block	0.53	0.0367	Active
0476002.MR	Littelfuse Inc.	2	250	125	Fast Blow	2-SMD, Square End Block	0.53	0.0448	Active
0476002.MRSN	Littelfuse Inc.	2	250	125	Fast Blow	2-SMD, Square End Block	0.53	0.0448	Active
3404.0012.11	SCHURTER Inc.	2	125	125	Fast Blow	2-SMD, J-Lead	0.44	Not Specified	Active
3404.0012.24	SCHURTER Inc.	2	125	125	Fast Blow	2-SMD, J-Lead	0.44	Not Specified	Active
0451.250MRL	Littelfuse Inc.	0.25	125	125	Fast Blow	2-SMD, Square End Block	0.0158	0.5765	Active

Engineering Selection Recommendations

For direct replacement of the obsolete SSQ 2, the 0679L2000-01 from Bel Fuse Inc. is the primary equivalent, maintaining identical electrical ratings and package geometry while offering active product status and AEC-Q200 automotive qualification.

The Littelfuse NANO²® 451 series (0451002.MRL, 0451002.MRSN, 0453002.MR) provides functionally equivalent substitutes with identical 2 A, 125 V AC/DC specifications and fast blow characteristics. These parts are widely available and carry active product status with CSA, PSE, and UL certifications.

The SCHURTER OMF 125 series (3404.0012.11, 3404.0012.24) offers electrical equivalence with 2 A, 125 V AC/DC ratings but uses a J-Lead package case instead of Square End Block. PCB layout modification is required for this substitution. Both variants carry cURus approval and active product status.

The Littelfuse NANO²® 476 series (0476002.MR, 0476002.MRSN) extends AC voltage rating to 250 V while maintaining 2 A current and 125 V DC rating. This substitution is suitable only for applications where elevated AC voltage capability is acceptable or beneficial.

The 0451.250MRL (250 mA) is not recommended as a direct substitute due to reduced current rating. This part is listed for reference only and requires circuit redesign validation.

Frequently Asked Questions (FAQ)

Q: Can the 0679L2000-01 be used as a direct replacement for SSQ 2?

A: Yes. The 0679L2000-01 maintains identical electrical specifications (2 A, 125 V AC/DC, fast blow) and package geometry (2-SMD, Square End Block). It is the primary equivalent for the obsolete SSQ 2.

Q: What is the difference between Littelfuse NANO²® 451 and NANO²® 453 series?

A: Both series meet the 2 A, 125 V AC/DC specification with identical melting I²t (0.53) and DC cold resistance (0.0367 Ω). The primary difference is series designation; both are functionally equivalent for the SSQ 2 application.

Q: Can SCHURTER 3404.0012 parts replace SSQ 2 without PCB modification?

A: No. The SCHURTER parts use a J-Lead package case versus the Square End Block of the SSQ 2. PCB footprint redesign is required for mechanical compatibility.

Q: Is the 0476002 series suitable for SSQ 2 replacement?

A: The 0476002 series (0476002.MR, 0476002.MRSN) maintains 2 A current and 125 V DC rating but increases AC voltage to 250 V. Substitution is valid only if the application circuit can tolerate or benefit from elevated AC voltage capability.

Q: Why is the 0451.250MRL listed if it cannot replace SSQ 2?

A: The 0451.250MRL is listed for reference as a related Littelfuse NANO²® product. Its 250 mA current rating makes it unsuitable as a direct substitute for the 2 A SSQ 2 and requires complete circuit validation before use.

Q: What certifications should I verify when selecting a substitute?

A: Verify that the selected substitute carries certifications required by your application region and industry standard. The SSQ 2 carries CE, CSA, and cULus approval. Equivalent parts carry CSA, UL, cURus, or PSE certifications depending on manufacturer and variant.

Q: Are all listed substitutes RoHS3 compliant?

A: Yes. All substitute parts listed are RoHS3 compliant and REACH unaffected, matching the environmental compliance status of the SSQ 2.

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