RUSB120 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The RUSB120 is a polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® series, rated for 6V maximum voltage with 1.2A hold current. This component is designed for overcurrent protection in through-hole radial disc configurations. The RUSB120 is currently listed as obsolete, making identification of active equivalent parts essential for ongoing design support and procurement continuity.

Substiute Parts

RUSB120

Littelfuse Inc.In Stock: 998RUSB120 Datasheet

Current PartRFQ

RUSBF120

Littelfuse Inc.In Stock: 872RUSBF120 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the RUSB120 is determined by strict equivalence across the following critical parameters:

• Voltage rating: 6V maximum
• Current hold specification: 1.2A maximum
• Current trip specification: 2A
• Maximum current capacity: 40A
• Time to trip: 500 milliseconds
• Initial resistance: 70 mOhms minimum
• Post-trip resistance: 140 mOhms maximum
• Mounting configuration: Through hole radial disc
• Physical dimensions: 0.272" diameter x 0.122" thickness (6.90mm x 3.10mm)
• Lead spacing: 0.201" (5.10mm)

The RUSBF120 meets all specified electrical and mechanical parameters and is classified as an active product, making it a direct functional equivalent for the obsolete RUSB120.

Parameter Comparison

Engineering Selection Recommendations

The RUSBF120 is the direct equivalent for the obsolete RUSB120. All electrical parameters, mechanical dimensions, and mounting specifications are identical. The RUSBF120 offers the following advantages:

• Active product status ensures long-term availability and supply chain continuity
• ROHS3 compliance meets current environmental and regulatory requirements
• Identical electrical performance across all specified parameters
• Same physical footprint and lead spacing for direct PCB compatibility
• Maintained certification by CSA, TUV, and UL approval agencies

For applications currently using the RUSB120, transition to the RUSBF120 is recommended without design modification.

Frequently Asked Questions (FAQ)

Q: Can the RUSBF120 be used as a direct replacement for the RUSB120?

A: Yes. The RUSBF120 is electrically and mechanically identical to the RUSB120 across all specified parameters, including voltage rating, current hold and trip specifications, resistance values, and physical dimensions. No circuit redesign is required.

Q: What is the difference between the RUSB120 and RUSBF120?

A: The primary differences are product status and compliance. The RUSB120 is obsolete and RoHS non-compliant, while the RUSBF120 is an active product with ROHS3 compliance. All electrical and mechanical specifications are equivalent.

Q: Are there any packaging differences between these parts?

A: The RUSB120 is supplied without specified packaging, while the RUSBF120 is supplied in bag packaging. Both components use identical radial disc through-hole configurations with the same lead spacing and physical dimensions.

Q: What certifications apply to the RUSBF120?

A: The RUSBF120 carries CSA, TUV, and UL approvals. The RUSB120 carried CSA, TUV, and UR approvals. Both meet industry safety standards for polymeric PTC resettable fuses.

Q: Is the RUSBF120 suitable for new designs?

A: Yes. The RUSBF120 is an active product with current manufacturing support, ROHS3 compliance, and full regulatory certifications. It is appropriate for both new designs and legacy system replacements.