RUSB155 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The RUSB155 is a polymeric PTC (Positive Temperature Coefficient) resettable fuse manufactured by Littelfuse Inc. under the PolySwitch® series. This component functions as an automatic reset protection device for circuits requiring overcurrent protection at 6V with a 1.55A hold current rating. The RUSB155 is classified as obsolete, making identification of active equivalent parts essential for new designs and ongoing system support. Substitute parts must maintain identical electrical characteristics and mechanical form factors to ensure direct compatibility in existing circuit designs.

Substiute Parts

RUSB155

Littelfuse Inc.In Stock: 987RUSB155 Datasheet

Current PartRFQ

RUSBF155

Littelfuse Inc.In Stock: 4950RUSBF155 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the RUSB155 is determined by strict equivalence across the following critical parameters:

• Voltage rating: 6V maximum
• Current hold (Ih): 1.55A maximum
• Current trip (It): 2.65A
• Time to trip: 2.2 seconds
• Initial resistance (Ri): 40 mOhms minimum
• Post-trip resistance (R1): 100 mOhms maximum
• Mounting configuration: Through hole radial disc package
• Physical dimensions: 0.272" diameter x 0.122" thickness with 0.201" lead spacing
• Polymeric PTC type classification

The RUSBF155 meets all these criteria and is classified as an active product, making it a direct functional equivalent for the obsolete RUSB155.

Parameter Comparison

Engineering Selection Recommendations

The RUSBF155 is the direct substitute for the obsolete RUSB155. Both components share identical electrical specifications and mechanical dimensions, ensuring pin-for-pin compatibility in existing circuit designs.

The RUSBF155 offers the advantage of active product status, meaning it is currently manufactured and available through standard distribution channels. Additionally, the RUSBF155 carries ROHS3 compliance, whereas the RUSB155 is RoHS non-compliant. For applications requiring RoHS compliance in new designs or system upgrades, the RUSBF155 is the appropriate selection.

Both parts maintain equivalent approval certifications from CSA and TUV. The RUSBF155 carries UL certification while the RUSB155 carries UR certification; both represent recognized safety standards for this component category.

Frequently Asked Questions (FAQ)

Q: Can RUSBF155 be used as a direct replacement for RUSB155 in existing designs?

A: Yes. The RUSBF155 is electrically and mechanically identical to the RUSB155. All critical parameters including voltage rating, current hold, current trip, time to trip, resistance values, and physical dimensions are equivalent. The components are pin-compatible and require no circuit modifications.

Q: What is the difference between RUSB155 and RUSBF155?

A: The primary differences are product status and RoHS compliance. The RUSB155 is obsolete and RoHS non-compliant. The RUSBF155 is an active product with ROHS3 compliance. Electrical and mechanical specifications are identical.

Q: Are there any packaging differences between these parts?

A: The RUSB155 is specified with dash packaging notation, while the RUSBF155 is supplied in bag packaging. Both components use the same radial disc through-hole form factor with identical dimensions and lead spacing.

Q: What certifications apply to the RUSBF155?

A: The RUSBF155 carries CSA, TUV, and UL approvals. These certifications confirm compliance with recognized safety standards for polymeric PTC resettable fuses in this voltage and current rating class.

Q: Is the RUSBF155 suitable for new product designs?

A: Yes. The RUSBF155 is an active product with current manufacturing support and ROHS3 compliance, making it appropriate for new designs requiring 6V, 1.55A polymeric PTC resettable fuse protection.