RXEF185K-AP Equivalent & Substitute Parts

Part Overview

The RXEF185K-AP is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., designed for 72V circuits with a 1.85A hold current rating. This component provides automatic overcurrent protection through thermal response, resetting when the fault condition is cleared. The part is actively produced and widely stocked, with 1122 units available in inventory. Alternative equivalent parts are available from the same manufacturer to support supply chain flexibility and design optimization across different packaging and certification requirements.

Key Parameters

Parameter	Value
Voltage - Max	72V
Current - Hold (Ih) (Max)	1.85 A
Current - Trip (It)	3.7 A
Current - Max	40 A
Time to Trip	12.6 s
Resistance - Initial (Ri) (Min)	80 mOhms
Resistance - Post Trip (R1) (Max)	190 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Type	Polymeric

Substitute Part Grouping Explanation

Substitution eligibility for the RXEF185K-AP is determined by strict equivalence across the following critical parameters:

Voltage rating: 72V maximum
Hold current (Ih): 1.85A maximum
Trip current (It): 3.7A
Time to trip: 12.6 seconds
Initial resistance (Ri): 80 mOhms minimum
Post-trip resistance (R1): 190 mOhms maximum
Operating temperature range: -40°C to 85°C
Mounting type: Through Hole
Package type: Radial, Disc configuration

The identified substitute parts maintain identical electrical performance specifications and mechanical mounting compatibility. Variations in physical dimensions (diameter and thickness) remain within acceptable tolerances for standard through-hole radial disc applications. All substitute parts are manufactured by Littelfuse Inc. and carry active product status.

Parameter Comparison

Parameter	RXEF185K-AP	72R185XMR	RXEF185-AP
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.
Series	PolySwitch®, RXEF	POLY-FUSE®, 72R	PolySwitch®, RXEF
Voltage - Max	72V	72V	72V
Current - Hold (Ih) (Max)	1.85 A	1.85 A	1.85 A
Current - Trip (It)	3.7 A	3.7 A	3.7 A
Current - Max	40 A	40 A	40 A
Time to Trip	12.6 s	12.6 s	12.6 s
Resistance - Initial (Ri) (Min)	80 mOhms	80 mOhms	80 mOhms
Resistance - Post Trip (R1) (Max)	190 mOhms	190 mOhms	190 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc
Type	Polymeric	Polymeric	Polymeric
Product Status	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Packaging	Cut Tape (CT)	Cut Tape (CT)	Cut Tape (CT)
Inventory	1122 Pcs	2836 Pcs	1089 Pcs

Engineering Selection Recommendations

All three parts—RXEF185K-AP, 72R185XMR, and RXEF185-AP—are electrically and functionally equivalent for 72V, 1.85A hold current applications. Selection between these parts should be based on the following factors:

Certification Coverage: RXEF185K-AP and RXEF185-AP carry CQC, CSA, TUV, and UL approvals. The 72R185XMR carries cURus and TUV approvals. Verify that the selected part meets all required regulatory certifications for your specific application and target markets.

Supply Availability: The 72R185XMR offers the highest inventory level at 2836 units, followed by RXEF185K-AP at 1122 units and RXEF185-AP at 1089 units. For high-volume production or extended lead-time mitigation, the 72R185XMR provides superior stock availability.

Physical Dimensions: Minor variations exist in diameter and thickness specifications. RXEF185K-AP and RXEF185-AP are within the PolySwitch® series with consistent lead spacing of 0.199" (5.05mm). The 72R185XMR exhibits slightly larger diameter (0.660" vs. 0.689") and lead spacing (0.201" vs. 0.199"), which remain compatible with standard through-hole radial disc footprints.

RoHS and Environmental Compliance: All parts are ROHS3 compliant with MSL rating of 1 (Unlimited). The 72R185XMR includes explicit REACH Unaffected status documentation.

Frequently Asked Questions (FAQ)

Q: Can RXEF185K-AP be directly replaced with 72R185XMR or RXEF185-AP?

A: Yes. All three parts maintain identical electrical specifications: 72V maximum voltage, 1.85A hold current, 3.7A trip current, 12.6-second trip time, and equivalent resistance characteristics. Through-hole radial disc mounting is consistent across all parts. Physical dimension variations are within acceptable tolerances for standard PCB footprints.

Q: What are the key differences between these substitute parts?

A: The primary differences are manufacturer series designation (PolySwitch® RXEF vs. POLY-FUSE® 72R), regulatory certifications (UL/CSA/CQC/TUV vs. cURus/TUV), and minor physical dimensions. Electrical performance and functional behavior are identical.

Q: Which part should I select for maximum supply chain security?

A: The 72R185XMR offers the highest inventory availability at 2836 units. If certification requirements mandate UL or CSA approval, select RXEF185K-AP or RXEF185-AP, which both carry these certifications.

Q: Are there any compatibility concerns with PCB footprints?

A: No. All parts use through-hole radial disc configuration with lead spacing within 0.199" to 0.201" (5.05mm to 5.10mm). Standard radial disc footprints accommodate all three parts without modification.

Q: Do all parts meet RoHS requirements?

A: Yes. All three parts are ROHS3 compliant with MSL rating 1 (Unlimited moisture sensitivity level).

Q: What certifications does each part carry?

A: RXEF185K-AP and RXEF185-AP carry CQC, CSA, TUV, and UL approvals. The 72R185XMR carries cURus and TUV approvals. Confirm that your application requirements align with the available certifications for your selected part.

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