RGEF400-AP Equivalent & Substitute Parts

Part Overview

The RGEF400-AP is a Polymeric PTC Resettable Fuse manufactured by Littelfuse, part of the PolySwitch® RGEF series. This component provides overcurrent protection with automatic reset capability in Through Hole Radial, Disc configuration. The part is Active status and widely used in circuit protection applications requiring reliable thermal response and electrical isolation. Substitute parts are identified to support procurement flexibility, inventory management, and design continuity.

Substiute Parts

RGEF400-AP

LittelfuseIn Stock: 3999RGEF400-AP Datasheet

Current PartRFQ

RGEF400-2

LittelfuseIn Stock: 8901RGEF400-2 Datasheet

SimilarRFQ

RGEF400K-AP

Littelfuse Inc.In Stock: 1479RGEF400K-AP Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the RGEF400-AP are identified based on strict electrical and mechanical parameter equivalence. The following criteria determine substitution validity:

Electrical Parameters (Critical):

• Voltage - Max: 16V
• Current - Hold (Ih) (Max): 4 A
• Current - Trip (It): 6.8 A
• Current - Max: 100 A
• Time to Trip: 1.7 s
• Resistance - Initial (Ri) (Min): 21 mOhms
• Resistance - Post Trip (R1) (Max): 60 mOhms
• Operating Temperature: -40°C ~ 85°C

Mechanical Parameters (Critical):

• Mounting Type: Through Hole
• Package / Case: Radial, Disc
• Size / Dimension: 0.331" L x 0.098" W (8.40mm x 2.50mm)
• Height - Seated (Max): 0.504" (12.80mm)
• Lead Spacing: 0.199" (5.05mm)

Compliance Parameters:

• Approval Agency: CSA, TUV, UL
• RoHS Status: ROHS3 Compliant

All identified substitutes match these parameters exactly and maintain the same functional classification within the PolySwitch® RGEF series.

Parameter Comparison

Engineering Selection Recommendations

All three parts—RGEF400-AP, RGEF400-2, and RGEF400K-AP—are Active status components manufactured by Littelfuse with identical electrical and mechanical specifications. Each part carries CSA, TUV, and UL approvals and maintains ROHS3 compliance. Selection between these parts is based on packaging designation and inventory availability rather than functional differences. RGEF400-AP and RGEF400K-AP are designated with suffix codes (-AP and -K-AP respectively), while RGEF400-2 uses a numeric suffix. All three are suitable for direct substitution in circuit protection applications requiring 16V, 4A hold current polymeric PTC resettable fuse functionality in Through Hole Radial configuration.

Frequently Asked Questions (FAQ)

Q: Can RGEF400-2 be used as a direct replacement for RGEF400-AP?

A: Yes. Both parts are electrically and mechanically identical, with matching voltage ratings (16V), hold current (4A), trip current (6.8A), operating temperature range (-40°C ~ 85°C), and physical dimensions (0.331" L x 0.098" W, 5.05mm lead spacing). Both are Through Hole Radial, Disc configuration with identical approval certifications.

Q: What is the difference between RGEF400-AP and RGEF400K-AP?

A: The parts are electrically and mechanically equivalent. The suffix designation (-AP versus -K-AP) indicates packaging or distribution channel coding from Littelfuse. All electrical parameters, thermal characteristics, and physical dimensions are identical.

Q: Are all three parts suitable for the same PCB layout?

A: Yes. All three parts share identical mounting type (Through Hole), package configuration (Radial, Disc), physical dimensions (0.331" L x 0.098" W), height (0.504" max), and lead spacing (0.199"). PCB footprints and assembly processes are interchangeable.

Q: Do these parts require different certifications or compliance documentation?

A: No. All three parts carry identical approvals (CSA, TUV, UL) and maintain ROHS3 compliance. Regulatory and compliance documentation is equivalent across all three part numbers.

Q: What is the hold current specification, and why is it important for substitution?

A: The hold current (Ih) is specified at 4A maximum for all three parts. This is the maximum continuous current the fuse can carry without tripping. Substitution requires matching this parameter to ensure the circuit operates within design specifications without nuisance trips.

Q: Can these parts be used interchangeably in high-temperature applications?

A: Yes. All three parts maintain the same operating temperature range of -40°C to 85°C. Temperature performance is identical across RGEF400-AP, RGEF400-2, and RGEF400K-AP.