MF-R050-0-99 Equivalent & Substitute Parts

Part Overview

The MF-R050-0-99 is a polymeric PTC resettable fuse manufactured by Bourns Inc. in the Multifuse® MF-R series. This component is rated for 60V maximum voltage with a 500 mA hold current and 1 A trip current, designed for through-hole radial mounting in disc configuration. The part is currently listed as obsolete, making identification of equivalent and substitute components essential for ongoing system support and new design implementations.

Key Parameters

Parameter	Value
Voltage - Max	60V
Current - Hold (Ih) (Max)	500 mA
Current - Trip (It)	1 A
Current - Max	40 A
Time to Trip	4 s
Resistance - Initial (Ri) (Min)	410 mOhms
Resistance - Post Trip (R1) (Max)	1.17 Ohms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.311" Dia x 0.122" T (7.90mm x 3.10mm)
Lead Spacing	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the MF-R050-0-99 is determined by strict equivalence across the following critical parameters:

Voltage - Max: 60V or higher
Current - Hold (Ih) (Max): 500 mA
Current - Trip (It): 1 A
Resistance - Initial (Ri) (Min): 410 mOhms
Resistance - Post Trip (R1) (Max): 1.17 Ohms
Operating Temperature: -40°C ~ 85°C
Mounting Type: Through Hole
Package / Case: Radial, Disc
Physical dimensions and lead spacing compatibility

Substitute parts are categorized as follows:

Parametric Equivalents (Same Voltage - 60V): MF-R050, MF-R050-0-17, and PFRA.050 maintain identical electrical specifications at 60V rating with matching hold current, trip current, and resistance characteristics.

Parametric Equivalents (Higher Voltage - 72V): MF-RX050/72-0 and MF-RX050/72-0-17 provide equivalent electrical performance with elevated voltage rating of 72V, suitable for applications requiring higher voltage tolerance while maintaining all other electrical parameters.

Direct Manufacturer Equivalent (Cross-Manufacturer): RXEF050 from Littelfuse Inc. operates at 72V with matching hold and trip current specifications, offering cross-manufacturer compatibility within the PolySwitch® RXEF series.

Parameter Comparison

Parameter	MF-R050-0-99	MF-R050	MF-R050-0-17	MF-RX050/72-0	MF-RX050/72-0-17	RXEF050	PFRA.050
Manufacturer	Bourns Inc.	Bourns Inc.	Bourns Inc.	Bourns Inc.	Bourns Inc.	Littelfuse Inc.	SCHURTER Inc.
Voltage - Max	60V	60V	60V	72V	72V	72V	60V
Current - Hold (Ih) (Max)	500 mA	500 mA	500 mA	500 mA	500 mA	500 mA	500 mA
Current - Trip (It)	1 A	1 A	1 A	1 A	1 A	1 A	1 A
Current - Max	40 A	40 A	40 A	40 A	40 A	40 A	40 A
Time to Trip	4 s	4 s	4 s	4 s	4 s	4 s	4 s
Resistance - Initial (Ri) (Min)	410 mOhms	410 mOhms	410 mOhms	410 mOhms	410 mOhms	500 mOhms	410 mOhms
Resistance - Post Trip (R1) (Max)	1.17 Ohms	1.17 Ohms	1.17 Ohms	1.17 Ohms	1.17 Ohms	1.17 Ohms	1.17 Ohms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-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	Through Hole	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc	Radial, Disc
Size / Dimension	0.311" Dia x 0.122" T (7.90mm x 3.10mm)	0.311" Dia x 0.122" T (7.90mm x 3.10mm)	0.311" Dia x 0.122" T (7.90mm x 3.10mm)	0.311" Dia x 0.122" T (7.90mm x 3.10mm)	0.311" Dia x 0.122" T (7.90mm x 3.10mm)	0.311" Dia x 0.118" T (7.90mm x 3.00mm)	0.311" Dia x 0.122" T (7.90mm x 3.10mm)
Lead Spacing	0.201" (5.10mm)	0.201" (5.10mm)	0.201" (5.10mm)	0.201" (5.10mm)	0.201" (5.10mm)	0.199" (5.05mm)	0.201" (5.10mm)
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
Approval Agency	cURus, TUV	cURus, TUV	cUL, cURus, TUV	cURus, TUV	cUL, cURus, TUV, UL	CQC, CSA, TUV, UL	cURus, TUV
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Same Voltage Rating): MF-R050 and MF-R050-0-17 from Bourns Inc. are active production alternatives to the obsolete MF-R050-0-99. Both maintain 60V voltage rating with identical electrical specifications. MF-R050-0-17 carries expanded approval certifications including cUL and UL, with AEC-Q200 automotive qualification rating.

For Higher Voltage Applications: MF-RX050/72-0 and MF-RX050/72-0-17 provide 72V rated alternatives while maintaining all other electrical parameters. MF-RX050/72-0-17 includes AEC-Q200 automotive qualification and expanded agency approvals (cUL, cURus, TUV, UL).

For Cross-Manufacturer Compatibility: RXEF050 from Littelfuse Inc. operates at 72V with matching hold and trip current specifications. This component carries broader international certifications (CQC, CSA, TUV, UL) and represents the PolySwitch® RXEF series alternative.

For SCHURTER Alternative: PFRA.050 from SCHURTER Inc. maintains 60V rating with identical electrical specifications and physical dimensions, offering cross-manufacturer sourcing within the same voltage class.

All substitute parts maintain ROHS3 compliance and identical operating temperature range (-40°C ~ 85°C). Physical dimensions and lead spacing are compatible across all listed alternatives, with minor thickness variation noted for RXEF050 (0.118" vs. 0.122").

Frequently Asked Questions (FAQ)

Q: Can MF-R050-0-17 directly replace MF-R050-0-99?

A: Yes. MF-R050-0-17 maintains identical electrical specifications (60V, 500 mA hold current, 1 A trip current, 410 mOhms initial resistance, 1.17 Ohms post-trip resistance) and physical dimensions. The primary difference is product status (active vs. obsolete) and expanded agency certifications on the -17 variant.

Q: What is the difference between 60V and 72V rated alternatives?

A: The 72V alternatives (MF-RX050/72-0, MF-RX050/72-0-17, RXEF050) provide higher voltage tolerance while maintaining identical hold current (500 mA), trip current (1 A), and resistance characteristics. These are suitable for applications requiring voltage headroom above 60V.

Q: Are there physical compatibility concerns with RXEF050?

A: RXEF050 has a thickness of 0.118" compared to 0.122" on other alternatives, and lead spacing of 0.199" versus 0.201". These minor dimensional variations may require board layout verification for tight mechanical constraints.

Q: Which substitute offers the broadest certification coverage?

A: MF-RX050/72-0-17 carries the most comprehensive agency approvals (cUL, cURus, TUV, UL) and includes AEC-Q200 automotive qualification. RXEF050 also provides broad certifications (CQC, CSA, TUV, UL) with cross-manufacturer sourcing.

Q: Is initial resistance variation significant between alternatives?

A: RXEF050 specifies 500 mOhms minimum initial resistance compared to 410 mOhms on other alternatives. This 90 mOhms difference may impact circuit performance in applications with tight resistance tolerances.

Q: Can these parts be used interchangeably in existing designs?

A: Electrical interchangeability is confirmed across all listed alternatives for the specified parameters. Physical dimensions and lead spacing are compatible. Design validation is required for applications with specific voltage requirements, resistance tolerances, or mechanical constraints.

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