RTEF135-2 Equivalent & Substitute Parts

Part Overview

The RTEF135-2 is a Polymeric PTC Resettable Fuse manufactured by Littelfuse Inc. in the PolySwitch® series, rated for 33V maximum voltage and 1.35A hold current. This component is classified as Obsolete, making identification of suitable substitute parts essential for ongoing design support and procurement continuity. The RTEF135-2 provides overcurrent protection through automatic resetting functionality in through-hole radial disc configuration.

Substiute Parts

RTEF135-2

Littelfuse Inc.In Stock: 745RTEF135-2 Datasheet

Current PartRFQ

RUEF135-2

LittelfuseIn Stock: 10931RUEF135-2 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

The RUEF135-2 qualifies as a direct substitute based on the following alignment criteria:

Matched Parameters:

• Current - Hold (Ih) (Max): 1.35 A (identical)
• Mounting Type: Through Hole (identical)
• Package / Case: Radial, Disc (identical)
• Lead Spacing: 0.199" (5.05mm) (identical)
• Series: PolySwitch® (same manufacturer family)
• RoHS3 Compliance: Both compliant
• Approval Agencies: Both certified by CSA, TUV, UL

Allowable Parameter Variations:

• Voltage - Max: 30V (RUEF135-2) vs 33V (RTEF135-2) — lower voltage rating is acceptable for applications operating within 30V maximum
• Current - Trip (It): 2.7 A (RUEF135-2) vs 2.5 A (RTEF135-2) — within acceptable tolerance for trip point variation
• Time to Trip: 7.3 s (RUEF135-2) vs 4.5 s (RTEF135-2) — longer response time acceptable depending on application requirements
• Resistance values: Minor variations within acceptable operating ranges

The RUEF135-2 is Active status, ensuring ongoing availability and supply chain support.

Parameter Comparison

Engineering Selection Recommendations

The RUEF135-2 is the qualified substitute for the obsolete RTEF135-2 based on functional equivalence and regulatory compliance. Both components carry CSA, TUV, and UL certifications, meeting industrial safety standards. The RUEF135-2 holds Active product status, ensuring long-term availability and supply chain reliability.

Selection of the RUEF135-2 is appropriate for applications where the circuit operates at or below 30V maximum voltage. The substitute's lower initial resistance (40 mOhms vs 59 mOhms) and extended time-to-trip characteristic (7.3 s vs 4.5 s) must be evaluated against specific application timing and thermal requirements. Both components maintain identical mechanical compatibility through matching lead spacing and radial disc package configuration.

Frequently Asked Questions (FAQ)

Q: Can RUEF135-2 directly replace RTEF135-2 in all applications?

A: Direct replacement is valid for circuits operating at maximum 30V. Applications requiring the full 33V rating of the original part require circuit redesign or alternative component selection.

Q: What is the significance of the different trip times (4.5 s vs 7.3 s)?

A: The RUEF135-2 exhibits a longer response time to overcurrent conditions. Applications with strict timing requirements for fault detection must evaluate whether this extended delay is acceptable for system protection strategy.

Q: Are the mechanical dimensions compatible?

A: Yes. Both components share identical lead spacing (0.199" / 5.05mm) and radial disc package configuration, ensuring PCB footprint compatibility without layout modification.

Q: Why does the RUEF135-2 have a higher maximum current rating (100 A vs 40 A)?

A: The maximum current rating reflects the component's thermal and mechanical limits under fault conditions. The hold current (1.35 A) and trip current (2.7 A) remain the primary design parameters for circuit protection function.

Q: Are both components RoHS compliant?

A: Yes. Both RTEF135-2 and RUEF135-2 are ROHS3 compliant and REACH unaffected, meeting environmental regulatory requirements.

Q: What certifications apply to the substitute part?

A: The RUEF135-2 carries CQC, CSA, TUV, and UL certifications, exceeding the certification scope of the original part and ensuring compliance with international safety standards.