72R135XF Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The 72R135XF is a polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the POLY-FUSE® 72R series. This through-hole radial disc component provides overcurrent protection at 72V with a 1.35 A hold current rating. The part is active in production and ROHS3 compliant. Substitute parts are identified to address inventory availability, packaging preferences, or alternative manufacturer sourcing requirements while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Voltage - Max	72V
Current - Hold (Ih) (Max)	1.35 A
Current - Trip (It)	2.7 A
Current - Max	40 A
Time to Trip	9.6 s
Resistance - Initial (Ri) (Min)	120 mOhms
Resistance - Post Trip (R1) (Max)	300 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Lead Spacing	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 72R135XF is determined by matching the following critical electrical parameters: maximum voltage (72V), hold current (1.35 A), trip current (2.7 A), maximum current (40 A), time to trip (9.6 s), initial resistance (120 mOhms minimum), and post-trip resistance (300 mOhms maximum). All identified substitutes maintain these electrical specifications identically.

Mechanical compatibility is verified through matching mounting type (through hole), package style (radial disc), and lead spacing (0.201" / 5.10mm). Minor variations in physical dimensions (diameter and thickness) are acceptable within the radial disc form factor, provided lead spacing remains consistent for PCB footprint compatibility.

All substitute parts are polymeric PTC type, active in production status, ROHS3 compliant, and rated for the -40°C to 85°C operating temperature range. Packaging format differences (bulk versus bag) do not affect electrical or mechanical performance.

Parameter Comparison

Parameter	72R135XF (Littelfuse)	RXEF135 (Littelfuse)	RXEF135K (Littelfuse)	MF-RX135/72-0 (Bourns)
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Bourns Inc.
Series	POLY-FUSE® 72R	PolySwitch® RXEF	PolySwitch® RXEF	Multifuse® MF-RX/72
Voltage - Max	72V	72V	72V	72V
Current - Hold (Ih) (Max)	1.35 A	1.35 A	1.35 A	1.35 A
Current - Trip (It)	2.7 A	2.7 A	2.7 A	2.7 A
Current - Max	40 A	40 A	40 A	40 A
Time to Trip	9.6 s	9.6 s	9.6 s	9.6 s
Resistance - Initial (Ri) (Min)	120 mOhms	120 mOhms	120 mOhms	120 mOhms
Resistance - Post Trip (R1) (Max)	300 mOhms	300 mOhms	300 mOhms	300 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc
Lead Spacing	0.201" (5.10mm)	0.199" (5.05mm)	0.199" (5.05mm)	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active	Active

Engineering Selection Recommendations

All four parts are active in production and ROHS3 compliant, meeting current regulatory requirements. Selection between the 72R135XF and its substitutes should be based on the following factors:

Littelfuse POLY-FUSE® 72R (72R135XF): Primary choice with cURus and TUV certifications. Bulk packaging format. Lead spacing 0.201" (5.10mm).

Littelfuse PolySwitch® RXEF (RXEF135 and RXEF135K): Alternative Littelfuse series with expanded certification scope (CQC, CSA, TUV, UL). Bag packaging format. Lead spacing 0.199" (5.05mm). RXEF135K offers identical electrical performance to RXEF135 with minor physical dimension variations.

Bourns Multifuse® MF-RX135/72-0: Cross-manufacturer alternative with cURus and TUV certifications. Bulk packaging format. Lead spacing 0.201" (5.10mm). Highest inventory availability (21,965 pcs).

All parts maintain identical electrical performance and operating characteristics. Physical dimension variations are within acceptable tolerances for radial disc through-hole mounting.

Frequently Asked Questions (FAQ)

Q: Can RXEF135 and RXEF135K be used interchangeably with 72R135XF?

A: Yes. Both PolySwitch® RXEF parts match all critical electrical parameters (72V, 1.35 A hold current, 2.7 A trip current, 9.6 s trip time) and mechanical specifications (through-hole radial disc, 0.199" lead spacing). Minor physical dimension differences do not affect PCB compatibility or performance.

Q: What is the difference between RXEF135 and RXEF135K?

A: Both parts are electrically identical with matching voltage, current, and resistance ratings. RXEF135K has a slightly smaller diameter (0.535" vs. 0.571") and different seated height (0.776" vs. 0.752"), but lead spacing remains consistent at 0.199" (5.05mm). Selection depends on available board space.

Q: Is the Bourns MF-RX135/72-0 a direct substitute?

A: Yes. The MF-RX135/72-0 matches all electrical specifications and maintains the same 0.201" (5.10mm) lead spacing as the 72R135XF. It is a cross-manufacturer alternative suitable for direct substitution.

Q: Are there certification differences between these parts?

A: The 72R135XF carries cURus and TUV approvals. The RXEF series (RXEF135 and RXEF135K) includes additional certifications: CQC, CSA, TUV, and UL. The MF-RX135/72-0 carries cURus and TUV approvals. All parts meet ROHS3 compliance requirements.

Q: Does packaging format (bulk vs. bag) affect electrical performance?

A: No. Packaging format is a logistics consideration only. Bulk and bag packaging contain identical components with identical electrical and mechanical specifications.

Q: What lead spacing should I verify for PCB compatibility?

A: The 72R135XF and MF-RX135/72-0 use 0.201" (5.10mm) lead spacing. The RXEF135 and RXEF135K use 0.199" (5.05mm) lead spacing. Verify your PCB footprint accommodates the selected part's lead spacing before assembly.

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