RXEF185-AP Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The RXEF185-AP is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., part of the PolySwitch® RXEF series. This component is designed for overcurrent protection in 72V circuits with a hold current of 1.85A and trip current of 3.7A. The device features a through-hole radial disc package suitable for PCB mounting in applications requiring automatic reset capability after fault conditions are cleared. The part maintains active product status with 1089 units in current inventory.

Substitute parts are identified when electrical parameters, mechanical compatibility, and regulatory compliance align with the original specification, enabling direct replacement in circuit designs without functional degradation.

Substiute Parts

RXEF185-AP

Littelfuse Inc.In Stock: 1185RXEF185-AP Datasheet

Current PartRFQ

72R185XMR

Littelfuse Inc.In Stock: 284672R185XMR Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the RXEF185-AP is determined by strict alignment of the following critical parameters:

Electrical Parameters (Non-Negotiable):

• Voltage rating: 72V maximum
• Hold current (Ih): 1.85A maximum
• Trip current (It): 3.7A
• Initial resistance (Ri): 80 mOhms minimum
• Post-trip resistance (R1): 190 mOhms maximum
• Time to trip: 12.6 seconds
• Maximum current capacity: 40A

Mechanical Parameters:

• Mounting type: Through hole
• Package configuration: Radial disc
• Operating temperature range: -40°C to 85°C

Regulatory Compliance:

• RoHS3 compliance required
• Moisture sensitivity level: 1 (Unlimited)

The substitute part 72R185XMR meets all electrical specifications and mechanical requirements, enabling direct functional replacement in circuit applications.

Parameter Comparison

Engineering Selection Recommendations

Both the RXEF185-AP and 72R185XMR are active products from Littelfuse Inc. with identical electrical performance specifications. Selection between these parts is based on the following factors:

Inventory Availability: The 72R185XMR maintains higher inventory levels (2836 units) compared to the RXEF185-AP (1089 units), providing supply chain advantages for high-volume applications.

Regulatory Compliance: Both parts meet RoHS3 requirements and carry TUV certification. The RXEF185-AP includes additional CSA and UL approvals, while the 72R185XMR carries cURus certification. Selection should align with specific application certification requirements.

Mechanical Fit: Dimensional variations between the two parts are minimal and within standard PCB mounting tolerances. Lead spacing differences (5.05mm vs 5.10mm) and height variations (22.40mm vs 23.00mm) do not impact functional compatibility in standard through-hole applications.

Series Designation: The RXEF185-AP belongs to the PolySwitch® RXEF series, while the 72R185XMR belongs to the POLY-FUSE® 72R series. Both series employ identical polymeric PTC technology with equivalent performance characteristics.

Frequently Asked Questions (FAQ)

Q: Can the 72R185XMR directly replace the RXEF185-AP in existing circuit designs?

A: Yes. Both parts share identical electrical specifications including voltage rating (72V), hold current (1.85A), trip current (3.7A), and resistance characteristics. Mechanical dimensions are within standard PCB mounting tolerances for through-hole radial disc packages.

Q: What are the key electrical parameters that define substitution compatibility?

A: The critical parameters are maximum voltage (72V), hold current (1.85A), trip current (3.7A), initial resistance (80 mOhms minimum), post-trip resistance (190 mOhms maximum), and time to trip (12.6 seconds). Any deviation from these specifications disqualifies a part as a direct substitute.

Q: Are there differences in regulatory certifications between these parts?

A: The RXEF185-AP carries CQC, CSA, TUV, and UL approvals. The 72R185XMR carries cURus and TUV approvals. Both meet RoHS3 compliance. Application requirements should determine which certification set is necessary.

Q: How do the physical dimensions compare?

A: The RXEF185-AP measures 0.689" diameter x 0.118" thickness (17.50mm x 3.00mm) with a seated height of 0.882" (22.40mm). The 72R185XMR measures 0.660" diameter x 0.122" thickness (16.76mm x 3.10mm) with a seated height of 0.906" (23.00mm). These variations are within standard PCB mounting tolerances and do not affect functional compatibility.

Q: What is the operating temperature range for both parts?

A: Both the RXEF185-AP and 72R185XMR operate across the temperature range of -40°C to 85°C, ensuring consistent performance across industrial and commercial applications.

Q: Which part should be selected for new designs?

A: Selection should be based on application-specific certification requirements and supply chain considerations. Both parts are active products with identical electrical performance. The 72R185XMR offers higher inventory availability, while the RXEF185-AP provides broader regulatory certifications.