MF-RX300 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The Bourns MF-RX300 is a polymeric PTC resettable fuse rated for 60V at 3A hold current, designed for through-hole radial mounting in disc configuration. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The MF-RX300 belongs to the Multifuse® MF-RX series and carries ROHS3 compliance with cURus and TUV approvals.

Key Parameters

Parameter	Value
Voltage - Max	60V
Current - Hold (Ih) (Max)	3 A
Current - Trip (It)	6 A
Current - Max	40 A
Time to Trip	19.8 s
Resistance - Initial (Ri) (Min)	40 mOhms
Resistance - Post Trip (R1) (Max)	100 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Lead Spacing	0.402" (10.20mm)
Type	Polymeric

Substitute Part Grouping Explanation

Substitution eligibility for the MF-RX300 is determined by the following critical parameters: voltage rating (maximum 60V for direct equivalents), current hold rating (3A), current trip rating (6A), time to trip (19.8s), initial resistance (40 mOhms minimum), post-trip resistance (100 mOhms maximum), operating temperature range (-40°C to 85°C), mounting type (through hole), package configuration (radial disc), and lead spacing (0.402" / 10.20mm).

Substitute parts are grouped into two categories:

Parametric Equivalents (Same Voltage Rating): Parts that match all electrical parameters and physical dimensions of the MF-RX300, differing only in product status or packaging format.

Direct Manufacturer Alternatives (Higher Voltage Rating or Different Dimensions): Parts from alternative manufacturers that maintain the same current, trip, and thermal characteristics but may have higher voltage ratings or minor dimensional variations. These are suitable for applications where the higher voltage rating provides additional design margin.

Parameter Comparison

Part Number	Manufacturer	Voltage - Max	Current - Hold (Ih)	Current - Trip (It)	Time to Trip	Ri (Min)	R1 (Max)	Product Status	Lead Spacing
MF-RX300	Bourns Inc.	60V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Obsolete	0.402" (10.20mm)
MF-RX300-005	Bourns Inc.	60V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Active	0.402" (10.20mm)
MF-RX300/72-0	Bourns Inc.	72V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Active	0.402" (10.20mm)
0ZRC0300FF1A	Bel Fuse Inc.	90V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Active	0.402" (10.20mm)
60R300XF	Littelfuse Inc.	60V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Active	0.402" (10.20mm)
PTR060V0300-TR	Eaton - Electronics Division	60V	3 A	6 A	19.8 s	40 mOhms	100 mOhms	Active	0.394" (10.00mm)

Engineering Selection Recommendations

Primary Recommendation - MF-RX300-005 (Bourns Inc.): This part is the direct parametric equivalent with identical electrical and mechanical specifications. It maintains active product status and carries the same ROHS3 compliance and cURus/TUV approvals as the original MF-RX300. This is the preferred choice for direct replacement in existing designs.

Alternative - 60R300XF (Littelfuse Inc., POLY-FUSE® 60R Series): Matches all electrical parameters and voltage rating with active product status. Carries ROHS3 compliance and cURus/TUV approvals. Minor dimensional variation in disc diameter (0.910" vs 0.980") requires PCB layout verification.

Alternative - PTR060V0300-TR (Eaton - Electronics Division): Matches all electrical parameters and voltage rating with active product status. Carries ROHS3 compliance and cURus/TUV approvals. Lead spacing is 0.394" (10.00mm) versus the original 0.402" (10.20mm), requiring footprint verification. Supplied in tape and reel packaging.

Higher Voltage Options - MF-RX300/72-0 (Bourns Inc., 72V) and 0ZRC0300FF1A (Bel Fuse Inc., 90V): Both maintain identical current, trip, and thermal characteristics with active product status and full compliance certifications. The 0ZRC0300FF1A carries AEC-Q200 automotive qualification. These are suitable for applications requiring design margin above 60V.

Frequently Asked Questions (FAQ)

Q: Can MF-RX300-005 be used as a direct drop-in replacement for MF-RX300?

A: Yes. MF-RX300-005 is a parametric equivalent with identical electrical specifications (60V, 3A hold, 6A trip, 19.8s trip time), physical dimensions, lead spacing (0.402"), and mounting configuration. The primary difference is active product status versus obsolete status.

Q: What is the difference between the Bourns MF-RX300/72-0 and the original MF-RX300?

A: The MF-RX300/72-0 has a maximum voltage rating of 72V compared to 60V for the MF-RX300. All other electrical parameters (current hold, trip, time to trip, resistance values) and physical dimensions are identical. The higher voltage rating provides additional design margin for applications operating near the 60V limit.

Q: Are there dimensional differences between substitute parts?

A: Minor variations exist. The 60R300XF has a disc diameter of 0.910" (23.11mm) versus 0.980" (24.90mm) for the MF-RX300. The PTR060V0300-TR has lead spacing of 0.394" (10.00mm) versus 0.402" (10.20mm). PCB footprint verification is required for these alternatives.

Q: What certifications do the substitute parts carry?

A: All substitute parts carry cURus and TUV approvals. The 0ZRC0300FF1A additionally carries AEC-Q200 automotive qualification. All are ROHS3 compliant and REACH unaffected.

Q: Can I use the 0ZRC0300FF1A (90V) in place of the MF-RX300 (60V)?

A: Yes, from an electrical standpoint. The 90V rating is backward compatible with 60V applications. The 0ZRC0300FF1A maintains identical current, trip, and thermal characteristics. Lead spacing is 0.402" (10.20mm), matching the original. Verify compliance requirements for your specific application, as this part carries AEC-Q200 automotive qualification.

Q: What is the difference between bulk and tape & reel packaging?

A: Bulk packaging is suitable for manual assembly or small-volume production. Tape & reel packaging (as with PTR060V0300-TR) is optimized for automated pick-and-place assembly equipment. Electrical and mechanical specifications are identical; packaging choice depends on assembly process requirements.

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