Bourns B1250T Equivalent & Substitute Parts

Part Overview

The Bourns B1250T is a 1.25A 600VAC board mount surface mount fuse designed for telecom applications. This component is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and component procurement. The B1250T operates within a temperature range of -55°C to 125°C and meets ROHS3 compliance requirements.

Substiute Parts

B1250T

Bourns Inc.In Stock: 26643B1250T Datasheet

Current PartRFQ

04611.25ER

Littelfuse Inc.In Stock: 23980204611.25ER Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the B1250T is determined by matching the following critical electrical and mechanical parameters:

• Current Rating: 1.25A (exact match required)
• Voltage Rating - AC: 600 VAC (minimum requirement)
• Mounting Type: Surface Mount
• Package / Case: 2-SMD, Square End Block
• Operating Temperature Range: -55°C to 125°C (minimum)
• RoHS Compliance: ROHS3 Compliant

The Littelfuse 04611.25ER meets all substitution criteria. While this part offers additional DC voltage rating capability (80 VDC) and enhanced breaking capacity specifications, these represent functional improvements rather than deviations from the core substitution parameters.

Parameter Comparison

Engineering Selection Recommendations

The Littelfuse 04611.25ER is the qualified substitute for the Bourns B1250T. Both components share identical current and AC voltage ratings, matching package geometry, and equivalent operating temperature specifications. The B1250T's obsolete status necessitates transition to the 04611.25ER, which maintains active product status and carries dual agency approval (CSA and UR) compared to the original UR-only certification.

Physical dimensions show minor variation (approximately 0.018" length and 0.003" width/height differences), which remains within typical PCB layout tolerances for 2-SMD board mount fuses. The 04611.25ER's additional DC voltage rating and enhanced breaking capacity provide functional compatibility without introducing incompatibility concerns for AC-primary telecom applications.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 04611.25ER directly replace the Bourns B1250T on existing PCBs?

A: Yes. Both components use identical 2-SMD, Square End Block packaging with compatible footprints. Minor dimensional variations (less than 0.02") do not affect PCB placement or soldering processes.

Q: What is the significance of the 04611.25ER's 80 VDC rating when the B1250T does not specify DC voltage?

A: The DC voltage rating represents additional capability. For applications operating exclusively at 600 VAC, this parameter does not affect substitution validity. The 04611.25ER remains fully compatible with the original AC-rated circuit requirements.

Q: How do the resistance and I²t values differ between these parts?

A: The B1250T exhibits 0.075 Ohms DC cold resistance and 17 I²t, while the 04611.25ER measures 0.11 Ohms and 16.5 I²t. These minor variations fall within acceptable tolerance ranges for 1.25A fuse performance and do not compromise circuit protection characteristics.

Q: Are both components RoHS compliant?

A: Yes. Both the B1250T and 04611.25ER meet ROHS3 compliance requirements and carry REACH Unaffected status.

Q: What certifications apply to the substitute part?

A: The Littelfuse 04611.25ER carries CSA and UR approvals, providing broader regulatory coverage than the original B1250T (UR only).