MQ 2.5TR Equivalent & Substitute Parts

Part Overview

The MQ 2.5TR is a 2.5 A board mount axial fuse rated for 125 V AC/DC operation, manufactured by Bel Fuse Inc. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing design support and procurement. The MQ 2.5TR serves applications requiring fast-blow fuse protection in through-hole configurations with axial package geometry.

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	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Breaking Capacity @ Rated Voltage	50 A AC, 300 A DC
Operating Temperature Range	-55°C ~ 125°C
Size / Dimension	0.125" Dia x 0.280" L (3.18 mm x 7.10 mm)
DC Cold Resistance	0.038 Ohms

Substitute Part Grouping Explanation

Substitution for the MQ 2.5TR is determined by strict equivalence across the following electrical and mechanical parameters:

Current Rating: 2.5 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Fast Blow (exact match required)
Mounting Type: Through Hole (exact match required)
Fuse Type: Board Mount, Cartridge Style Excluded (exact match required)
Package / Case: Axial (exact match required)
Breaking Capacity: 50 A AC, 300 A DC (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

Two substitute parts meet these criteria. Both are manufactured by Littelfuse Inc. and belong to the PICO® II 251 series. The substitutes differ in packaging format (Cut Tape vs. Bulk) and minor dimensional variations in lead diameter, which do not affect electrical performance or board mount compatibility.

Parameter Comparison

Parameter	MQ 2.5TR (Bel Fuse Inc.)	025102.5NRT1L (Littelfuse Inc.)	025102.5MXL (Littelfuse Inc.)
Current Rating (Amps)	2.5 A	2.5 A	2.5 A
Voltage Rating - AC	125 V	125 V	125 V
Voltage Rating - DC	125 V	125 V	125 V
Response Time	Fast Blow	Fast Blow	Fast Blow
Mounting Type	Through Hole	Through Hole	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)
Package / Case	Axial	Axial	Axial
Breaking Capacity @ Rated Voltage	50 A AC, 300 A DC	50 A AC, 300 A DC	50 A AC, 300 A DC
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Size / Dimension	0.125" Dia x 0.280" L (3.18 mm x 7.10 mm)	0.110" Dia x 0.280" L (2.80 mm x 7.11 mm)	0.110" Dia x 0.280" L (2.80 mm x 7.11 mm)
DC Cold Resistance	0.038 Ohms	0.036 Ohms	0.036 Ohms
Melting I²t	0.59	0.721	0.721
Product Status	Obsolete	Active	Active
Approval Agency	CE, CSA, cURus	CCC, CSA, cURus, PSE, TUV	CCC, CSA, cURus, PSE, TUV
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Both Littelfuse substitutes (025102.5NRT1L and 025102.5MXL) are electrically and mechanically equivalent to the obsolete MQ 2.5TR across all critical parameters. Selection between the two substitutes is determined by packaging requirements:

025102.5NRT1L: Specified for Cut Tape (CT) packaging. Suitable for automated assembly processes and tape-and-reel handling.
025102.5MXL: Specified for Bulk packaging. Suitable for manual assembly or applications where tape packaging is not required.

Both substitutes carry active product status from Littelfuse Inc., ensuring long-term availability and supply chain continuity. Both meet expanded approval certifications (CCC, CSA, cURus, PSE, TUV) compared to the original part and comply with ROHS3 requirements. The minor differences in lead diameter (0.110" vs. 0.125") and melting I²t values (0.721 vs. 0.59) do not affect functional compatibility in applications designed for the MQ 2.5TR.

Frequently Asked Questions (FAQ)

Q: Can 025102.5NRT1L and 025102.5MXL be used interchangeably with MQ 2.5TR?

A: Both Littelfuse parts are electrically and mechanically equivalent to the MQ 2.5TR. They share identical current ratings, voltage ratings, response time, mounting type, and breaking capacity. The primary difference is packaging format (Cut Tape vs. Bulk), which does not affect electrical performance or board mount compatibility.

Q: What is the difference between 025102.5NRT1L and 025102.5MXL?

A: Both parts are from the PICO® II 251 series and are electrically identical. The difference is packaging: 025102.5NRT1L is supplied in Cut Tape format for automated assembly, while 025102.5MXL is supplied in Bulk format. Select based on your assembly process requirements.

Q: Why does the MQ 2.5TR show as obsolete?

A: The MQ 2.5TR is classified as obsolete by Bel Fuse Inc. The Littelfuse substitutes (025102.5NRT1L and 025102.5MXL) are active products with confirmed ongoing availability, making them the recommended alternatives for new designs and ongoing procurement.

Q: Are there compliance differences between MQ 2.5TR and the substitutes?

A: The Littelfuse substitutes carry broader approval certifications (CCC, CSA, cURus, PSE, TUV) compared to the original part (CE, CSA, cURus). Both substitutes are ROHS3 compliant, whereas the original part does not specify RoHS status. These differences represent improved compliance coverage.

Q: Do the dimensional differences affect PCB layout?

A: The lead diameter difference (0.125" vs. 0.110") is minor and does not affect standard through-hole PCB pad sizing. The axial length remains equivalent at 0.280" (7.10 mm vs. 7.11 mm). Existing PCB designs for MQ 2.5TR accommodate the Littelfuse substitutes without modification.

Q: What is the significance of the melting I²t difference?

A: The melting I²t values (0.59 for MQ 2.5TR vs. 0.721 for substitutes) reflect thermal characteristics during fault conditions. Both values are within the operating envelope for 2.5 A fast-blow fuses and do not affect functional compatibility in applications designed for the MQ 2.5TR.

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