RUSBF250 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The RUSBF250 is an active polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® RUSBF series. This component provides overcurrent protection with automatic reset capability in through-hole radial disc configuration. The part is rated for 16V maximum voltage with 2.5A hold current and 5A trip current. Finding equivalent substitute parts is necessary when managing inventory constraints, lead time requirements, or when alternative sourcing becomes advantageous while maintaining circuit protection specifications.

Substiute Parts

RUSBF250

Littelfuse Inc.In Stock: 790RUSBF250 Datasheet

Current PartRFQ

MF-R250-0-10

Bourns Inc.In Stock: 5867MF-R250-0-10 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the RUSBF250 is determined by the following critical parameters:

Mandatory Compatibility Criteria:

• Polymeric PTC resettable fuse type
• Through hole radial disc mounting configuration
• Current hold rating of 2.5A maximum
• Current trip rating of 5A
• Maximum voltage rating equal to or greater than 16V
• Operating temperature range of -40°C to 85°C
• ROHS3 compliance

The substitute part MF-R250-0-10 from Bourns Inc. meets these criteria with identical hold and trip current specifications, matching operating temperature range, and equivalent compliance certifications. The higher voltage rating (30V) of the substitute provides additional design margin without compromising circuit protection function.

Parameter Comparison

Engineering Selection Recommendations

Both the RUSBF250 and MF-R250-0-10 are active products with ROHS3 compliance and regulatory approvals suitable for industrial applications. The RUSBF250 carries CSA, TUV, and UL certifications, while the MF-R250-0-10 carries cURus and TUV certifications. Selection between these parts should be based on specific circuit voltage requirements and required approval agencies for the end application. The MF-R250-0-10 offers higher voltage rating capability (30V versus 16V), making it suitable for circuits operating at or below 16V with additional design margin. Initial resistance and post-trip resistance values differ slightly between parts but remain within acceptable ranges for overcurrent protection function.

Frequently Asked Questions (FAQ)

Q: Can MF-R250-0-10 directly replace RUSBF250 in a 16V circuit?

A: Yes. The MF-R250-0-10 has a 30V maximum voltage rating, which exceeds the 16V requirement of the RUSBF250. Both parts share identical current hold (2.5A) and trip (5A) specifications, matching operating temperature range, and equivalent polymeric PTC technology. The higher voltage rating does not affect functionality in lower voltage applications.

Q: What are the key differences between these substitute parts?

A: The primary differences are manufacturer (Littelfuse versus Bourns), voltage rating (16V versus 30V), initial resistance (20 mOhms versus 25 mOhms), post-trip resistance (60 mOhms versus 70 mOhms), time to trip (40s versus 10.3s), and regulatory certifications. Current ratings, mounting type, package configuration, and operating temperature range are identical.

Q: Are the physical dimensions compatible for PCB mounting?

A: Both parts use through-hole radial disc configuration. The RUSBF250 has 0.118" (3.00mm) lead spacing, while the MF-R250-0-10 has 0.201" (5.10mm) lead spacing. PCB footprint compatibility must be verified before substitution. Length dimensions are similar (11.40mm versus 12.00mm), and both have 0.720" (18.30mm) maximum seated height.

Q: Which certifications should I prioritize for my application?

A: The RUSBF250 carries CSA, TUV, and UL approvals. The MF-R250-0-10 carries cURus and TUV approvals. Select the part whose certification set matches your application requirements and regional standards.

Q: Does the difference in time to trip (40s versus 10.3s) affect circuit protection?

A: Time to trip indicates the response speed to overcurrent conditions. The MF-R250-0-10 responds faster (10.3s) compared to the RUSBF250 (40s). This difference should be evaluated against your circuit's overcurrent tolerance and protection requirements.