RUEF400-1 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The RUEF400-1 is a polymeric PTC resettable fuse manufactured by Littelfuse, part of the PolySwitch® RUEF series. This component provides overcurrent protection with automatic reset capability in through-hole radial configuration. The device is rated for 30V maximum voltage and 4A hold current, with a trip current of 8A. As an active product with full compliance certifications (CQC, CSA, TUV, UL), it remains in production. Identifying equivalent substitute parts is essential for supply chain continuity, inventory optimization, and design flexibility when the primary part number becomes unavailable or when alternative sourcing is required.

Substiute Parts

RUEF400-1

LittelfuseIn Stock: 1502RUEF400-1 Datasheet

Current PartRFQ

RUEF400

LittelfuseIn Stock: 3479RUEF400 Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the RUEF400-1 is determined by strict equivalence across the following critical parameters:

Electrical specifications: Maximum voltage (30V), hold current rating (4A), trip current (8A), maximum current capacity (100A), and time-to-trip characteristic (12.7s) must match exactly. Resistance parameters—initial resistance minimum (10 mOhms) and post-trip resistance maximum (50 mOhms)—define the electrical behavior during normal operation and fault conditions.

Mechanical and thermal specifications: Operating temperature range (-40°C to 85°C), mounting type (through hole), package configuration (radial disc), and lead spacing (0.199" / 5.05mm) ensure physical and thermal compatibility with existing circuit board designs.

Product classification: The component must be polymeric PTC type within the PolySwitch® RUEF series to maintain functional equivalence.

Compliance and certification: All substitute parts must maintain the same approval agency certifications (CQC, CSA, TUV, UL) and regulatory compliance status (ROHS3 Compliant, REACH Unaffected).

Parameter Comparison

Engineering Selection Recommendations

The RUEF400 is a direct parametric equivalent to the RUEF400-1. Both components are manufactured by Littelfuse within the PolySwitch® RUEF series and share identical electrical, mechanical, and thermal specifications. Both maintain active product status with full compliance certifications from CQC, CSA, TUV, and UL. ROHS3 compliance and REACH unaffected status are consistent across both part numbers.

Selection between RUEF400-1 and RUEF400 may be based on inventory availability and supply chain considerations. The RUEF400 currently maintains higher inventory levels (3400 pcs) compared to RUEF400-1 (1417 pcs), which may influence procurement decisions for high-volume applications or extended lead-time mitigation strategies.

Frequently Asked Questions (FAQ)

Q: Can RUEF400 be used as a direct replacement for RUEF400-1?

A: Yes. Both components are parametrically identical across all electrical, mechanical, thermal, and compliance specifications. They are interchangeable in circuit design and PCB layout without modification.

Q: Are there any differences in performance or reliability between these part numbers?

A: No. Both parts are manufactured by Littelfuse using identical specifications. Performance characteristics, including hold current (4A), trip current (8A), time-to-trip (12.7s), and operating temperature range (-40°C to 85°C), are identical.

Q: Do both parts meet the same regulatory certifications?

A: Yes. Both RUEF400-1 and RUEF400 carry identical approval agency certifications (CQC, CSA, TUV, UL) and comply with ROHS3 and REACH requirements.

Q: What is the physical compatibility between these parts?

A: Both components use identical through-hole radial disc packaging with matching lead spacing (0.199" / 5.05mm), dimensions (0.551" L x 0.118" W), and seated height (0.760"). They are mechanically interchangeable on PCBs designed for either part number.

Q: Which part should be selected for new designs?

A: Either part number is suitable for new designs. Selection may be based on current inventory availability, supplier preference, or supply chain strategy. Both maintain active product status with equivalent long-term availability.