72R030XU Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The Littelfuse 72R030XU is a polymeric PTC resettable fuse rated for 72V maximum voltage with 300 mA hold current. This component is classified as obsolete, making equivalent substitutes necessary for ongoing design support and procurement. The 72R series POLY-FUSE® devices provide overcurrent protection in through-hole radial disc configuration and are suitable for applications requiring automatic reset functionality after fault conditions.

Key Parameters

Parameter	Value
Voltage - Max	72V
Current - Hold (Ih) (Max)	300 mA
Current - Trip (It)	600 mA
Current - Max	40 A
Time to Trip	3 s
Resistance - Initial (Ri) (Min)	880 mOhms
Resistance - Post Trip (R1) (Max)	2.1 Ohms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.291" Dia x 0.122" T (7.40mm x 3.10mm)
Lead Spacing	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 72R030XU is determined by strict equivalence across the following critical parameters:

Voltage rating: 72V maximum
Hold current (Ih): 300 mA maximum
Trip current (It): 600 mA
Time to trip: 3 seconds
Post-trip resistance (R1): 2.1 Ohms maximum
Operating temperature range: -40°C to 85°C
Mounting configuration: Through hole radial disc
Lead spacing: 5.10mm nominal
RoHS3 compliance

Two active alternatives meet these criteria and are available as direct substitutes for the obsolete 72R030XU.

Parameter Comparison

Parameter	72R030XU (Littelfuse)	RXEF030S (Littelfuse)	MF-RX030/72-0 (Bourns)
Manufacturer	Littelfuse	Littelfuse	Bourns Inc.
Series	POLY-FUSE®, 72R	PolySwitch®, RXEF	Multifuse®, MF-RX/72
Product Status	Obsolete	Active	Active
Voltage - Max	72V	72V	72V
Current - Hold (Ih) (Max)	300 mA	300 mA	300 mA
Current - Trip (It)	600 mA	600 mA	600 mA
Current - Max	40 A	40 A	40 A
Time to Trip	3 s	3 s	3 s
Resistance - Initial (Ri) (Min)	880 mOhms	880 mOhms	760 mOhms
Resistance - Post Trip (R1) (Max)	2.1 Ohms	2.1 Ohms	2.1 Ohms
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
Size / Dimension	0.291" Dia x 0.122" T (7.40mm x 3.10mm)	0.291" Dia x 0.118" T (7.40mm x 3.00mm)	0.291" Dia x 0.122" T (7.40mm x 3.10mm)
Height - Seated (Max)	0.500" (12.70mm)	0.500" (12.70mm)	0.528" (13.40mm)
Lead Spacing	0.201" (5.10mm)	0.199" (5.05mm)	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	cURus, TUV	CQC, CSA, TUV, UL	cURus, TUV

Engineering Selection Recommendations

Both RXEF030S and MF-RX030/72-0 are functionally equivalent substitutes for the obsolete 72R030XU based on electrical parameter matching.

RXEF030S (Littelfuse PolySwitch®): This part maintains active product status within the same manufacturer family. It carries expanded regulatory approvals including CQC, CSA, TUV, and UL certification. The thickness specification is 0.118" (3.00mm) compared to the original 0.122" (3.10mm), representing a 0.10mm reduction. Lead spacing is 0.199" (5.05mm) versus the original 0.201" (5.10mm). These dimensional variations are within typical PCB layout tolerances for through-hole radial components.

MF-RX030/72-0 (Bourns Multifuse®): This alternative provides equivalent electrical performance with identical dimensional footprint to the original part (0.291" diameter, 0.122" thickness, 0.201" lead spacing). Initial resistance is specified at 760 mOhms minimum, which is lower than the 880 mOhms minimum of the original. Seated height is 0.528" (13.40mm) compared to 0.500" (12.70mm), a 0.70mm increase. Both parts carry cURus and TUV approvals.

Selection between these substitutes depends on PCB layout constraints and regulatory certification requirements for the end application.

Frequently Asked Questions (FAQ)

Q: Can RXEF030S be used as a direct replacement for 72R030XU without PCB modification?

A: RXEF030S is electrically equivalent and mechanically compatible for most applications. The thickness difference of 0.10mm and lead spacing difference of 0.05mm are within standard PCB through-hole tolerances. Verify clearance in confined spaces or high-density layouts.

Q: What is the significance of the initial resistance (Ri) difference between MF-RX030/72-0 (760 mOhms) and the original 72R030XU (880 mOhms)?

A: Both values fall within acceptable operating ranges for this device class. The lower initial resistance of the Bourns part results in slightly lower voltage drop during normal operation. This difference is not functionally significant for overcurrent protection performance.

Q: Are there any compliance or certification differences between the substitutes?

A: RXEF030S carries broader regulatory approvals (CQC, CSA, TUV, UL) compared to MF-RX030/72-0 (cURus, TUV). Both are ROHS3 compliant. Select based on specific certification requirements of your application or end market.

Q: Does the seated height difference of MF-RX030/72-0 (0.528" vs. 0.500") affect PCB assembly?

A: The 0.028" (0.70mm) increase in seated height may impact clearance in applications with tight vertical constraints. Verify component clearance above the PCB surface in your specific assembly configuration.

Q: What is the packaging difference between these substitutes?

A: 72R030XU is listed as "-" (unspecified), RXEF030S is supplied in Bag packaging, and MF-RX030/72-0 is supplied in Bulk packaging. Confirm packaging requirements for your procurement and assembly processes.

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