UMTS 1.25 Equivalent & Substitute Parts

Part Overview

The UMTS 1.25 is a 1.25 A, 250 V AC surface mount board fuse manufactured by Bel Fuse Inc. in a 2-SMD, Square End Block package. This component is classified as Obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and procurement continuity. The fuse provides slow-blow response characteristics suitable for board-level overcurrent protection in industrial and electrical applications.

Substiute Parts

UMTS 1.25

Bel Fuse Inc.In Stock: 2568UMTS 1.25 Datasheet

Current PartRFQ

04431.25ERE

Littelfuse Inc.In Stock: 370204431.25ERE Datasheet

SimilarRFQ

TR-1245UMFT1-25-R

Eaton - Electronics DivisionIn Stock: 3788TR-1245UMFT1-25-R Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the UMTS 1.25 are qualified based on the following critical parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating - AC: 250 V (minimum requirement)
• Response Time: Slow Blow (functional characteristic)
• Mounting Type: Surface Mount (assembly compatibility)
• Package / Case: 2-SMD, Square End Block (footprint compatibility)
• RoHS Compliance: ROHS3 Compliant (regulatory requirement)

Two active substitute parts meet these criteria and are available in production inventory.

Parameter Comparison

Engineering Selection Recommendations

Both substitute parts are Active products with current manufacturing support, addressing the obsolescence status of the UMTS 1.25.

The 04431.25ERE (Littelfuse NANO²® 443E series) provides the highest breaking capacity at 200 A and includes dual voltage rating (250 V AC/DC). This part carries broader approval agency coverage (CQC, cURus, VDE) and is available in higher inventory quantities (3600 pcs). The smaller physical dimensions (10.08 x 3.05 x 3.05 mm) may require PCB layout verification for footprint compatibility.

The TR-1245UMFT1-25-R (Eaton 1245UMFT series) maintains dimensional compatibility closest to the original UMTS 1.25 (12.10 x 4.50 x 4.50 mm versus 12.10 x 4.45 x 4.45 mm). This part carries cURus approval and is suitable for applications where existing PCB layouts cannot accommodate dimensional changes.

Both substitutes meet RoHS3 compliance and maintain the required slow-blow response characteristic and 1.25 A current rating.

Frequently Asked Questions (FAQ)

Q: Can the 04431.25ERE be used as a direct replacement for the UMTS 1.25 on existing PCBs?

A: The 04431.25ERE has different physical dimensions (10.08 x 3.05 x 3.05 mm versus 12.10 x 4.45 x 4.45 mm). PCB footprint compatibility must be verified before substitution. If the existing footprint cannot accommodate the smaller package, the TR-1245UMFT1-25-R is dimensionally closer.

Q: What is the significance of the melting I²t values in the parameter comparison?

A: Melting I²t indicates the thermal energy required to melt the fuse element. Lower values (04431.25ERE at 3.97) indicate faster thermal response, while higher values (UMTS 1.25 at 7) indicate slower thermal response. All three parts are rated as slow-blow, but the 04431.25ERE will respond more quickly to sustained overcurrent conditions.

Q: Are there voltage rating differences between the substitutes?

A: The UMTS 1.25 and TR-1245UMFT1-25-R are rated for 250 V AC only. The 04431.25ERE is rated for 250 V AC and 250 V DC. For AC-only applications, all three parts are equivalent. For DC applications, only the 04431.25ERE is specified.

Q: Which substitute has the best approval agency coverage?

A: The 04431.25ERE carries approvals from CQC, cURus, and VDE. The UMTS 1.25 carries CE, cULus, and UMF approvals. The TR-1245UMFT1-25-R carries cURus approval only. Approval requirements depend on the target market and application standards.

Q: What is the impact of DC cold resistance differences?

A: DC cold resistance affects voltage drop during normal operation. The UMTS 1.25 has the lowest resistance at 0.065 Ohms, followed by the TR-1245UMFT1-25-R at 0.085 Ohms, and the 04431.25ERE at 0.1 Ohms. For low-current applications, these differences are negligible. For applications with sustained high current near the 1.25 A rating, the lower resistance of the original part may be preferred.