FCD121125TP Equivalent & Substitute Parts

Part Overview

The FCD121125TP is a surface mount board-mounted fuse manufactured by Littelfuse Inc., rated at 1.25 A and 50 V DC with fast-blow response characteristics. This component is classified as obsolete, making identification of equivalent substitute parts essential for ongoing design support and production continuity. The part is packaged in 1206 (3216 Metric) form factor and meets ROHS3 compliance requirements.

Substiute Parts

FCD121125TP

Littelfuse Inc.In Stock: 1044FCD121125TP Datasheet

Current PartRFQ

04371.25WR

Littelfuse Inc.In Stock: 383904371.25WR Datasheet

DirectRFQ

04661.25NR

Littelfuse Inc.In Stock: 1037904661.25NR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FCD121125TP are qualified based on the following electrical and mechanical parameters:

• Current Rating: 1.25 A (exact match required)
• Fuse Type: Board Mount (Cartridge Style Excluded)
• Mounting Type: Surface Mount
• Package / Case: 1206 (3216 Metric)
• Response Time: Fast Blow
• Breaking Capacity @ Rated Voltage: 50 A minimum
• Voltage Rating: Must support minimum 50 V DC operation

The substitute parts listed below meet these core criteria while offering enhanced voltage ratings (63 V AC/DC) and active product status, providing improved design flexibility and supply chain availability.

Parameter Comparison

Engineering Selection Recommendations

Both substitute parts (04371.25WR and 04661.25NR) are active products from Littelfuse Inc. with current manufacturing status, addressing the obsolescence of the FCD121125TP. Both substitutes maintain the 1.25 A current rating and 1206 package form factor while providing enhanced voltage ratings of 63 V AC/DC, which exceeds the original 50 V DC specification and ensures compatibility in applications operating at or below the original voltage level.

The 04661.25NR (SlimLine™ 466 series) offers a manufacturer-recommended upgrade path with improved thermal characteristics and lower DC cold resistance (0.059 Ohms versus 0.318 Ohms for the 04371.25WR), supporting applications with tighter resistance tolerances. Both parts carry CSA and UL/UR certifications and maintain ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can the substitute parts be used directly in place of the FCD121125TP?

A: Yes. Both substitute parts maintain the critical electrical parameters (1.25 A current rating, fast-blow response, 50 A breaking capacity) and mechanical compatibility (1206 surface mount package). The enhanced 63 V voltage rating provides additional design margin for applications originally specified at 50 V DC.

Q: What is the difference between the two substitute parts?

A: Both parts share identical current and voltage ratings. The 04661.25NR (SlimLine™ 466) features lower DC cold resistance (0.059 Ohms) and smaller physical dimensions compared to the 04371.25WR (437 series, 0.318 Ohms). The 04661.25NR is the manufacturer-recommended upgrade.

Q: Are there any thermal operating range differences?

A: The FCD121125TP operates from -55°C to 125°C. The 04371.25WR extends to -55°C to 150°C, while the 04661.25NR operates from -55°C to 90°C. Application thermal requirements should be evaluated against these ranges.

Q: Do the substitute parts maintain the same package footprint?

A: Both substitute parts use the 1206 (3216 Metric) package. Physical dimensions vary slightly: the 04661.25NR is more compact (0.125" L x 0.060" W x 0.023" H) compared to the FCD121125TP (0.126" L x 0.063" W x 0.024" H), while the 04371.25WR is slightly taller (0.032" H). PCB layout verification is recommended for space-constrained applications.

Q: What certifications apply to the substitute parts?

A: The 04371.25WR carries CSA and UR approvals. The 04661.25NR carries CSA and UL approvals. Both maintain ROHS3 compliance and REACH unaffected status.