MF-LR730 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The MF-LR730 is a polymeric PTC resettable fuse manufactured by Bourns Inc. in the Multifuse® MF-LR series. This component provides overcurrent protection with a hold current of 7.3 A at a maximum voltage rating of 10V. The device is actively produced and stocked, with 1,028 units available in inventory. Substitute parts are identified when equivalent electrical performance is required but the original part becomes unavailable, when alternative voltage ratings are needed for system design flexibility, or when supply chain optimization is necessary.

Substiute Parts

MF-LR730

Bourns Inc.In Stock: 1134MF-LR730 Datasheet

Current PartRFQ

LR4-730F

Littelfuse Inc.In Stock: 3205LR4-730F Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MF-LR730 is determined by the following critical parameters:

Electrical Compatibility Parameters:

• Current - Hold (Ih): Must match at 7.3 A maximum
• Current - Trip (It): Must match at 14.1 A
• Time to Trip: Must match at 5 seconds
• Resistance - Initial (Ri): Must match at 6 mOhms minimum
• Resistance - Post Trip (R1): Must match at 15 mOhms maximum
• Operating Temperature Range: Must support -40°C ~ 85°C

Mechanical Compatibility Parameters:

• Package / Case: Must be Strap configuration
• Thickness (Max): Must not exceed 0.039" (1.00mm)

Regulatory & Compliance Parameters:

• Type: Must be Polymeric
• RoHS Status: Must maintain ROHS3 Compliance
• Approval Agencies: Must include relevant certifications (cURus, TUV, UL, CSA)

The substitute part LR4-730F from Littelfuse Inc. meets all electrical parameters and mechanical constraints. The voltage rating difference (20V vs. 10V) represents an uprated specification that maintains backward compatibility in applications designed for 10V operation, as the component can safely operate at lower voltages within its rated range.

Parameter Comparison

Engineering Selection Recommendations

The LR4-730F from Littelfuse Inc. (PolySwitch® LR4 series) is a direct functional equivalent to the MF-LR730. Both components are active products with current manufacturing status and full regulatory compliance under ROHS3 standards.

Selection Criteria:

The LR4-730F is suitable for applications currently specified for the MF-LR730 based on:

• Identical electrical performance across all critical parameters (hold current, trip current, response time, and resistance characteristics)
• Mechanical compatibility in strap package configuration with matching thickness specifications
• Enhanced voltage rating (20V vs. 10V) providing design margin for systems operating at or below 10V
• Broader certification coverage (CSA, TUV, UL vs. cURus, TUV) supporting wider regulatory requirements
• Equivalent moisture sensitivity level (MSL 1 - Unlimited) and REACH compliance status

Both components are manufactured from polymeric PTC material and operate across the identical temperature range of -40°C to 85°C.

Frequently Asked Questions (FAQ)

Q: Can the LR4-730F replace the MF-LR730 in existing designs?

A: Yes. The LR4-730F meets all electrical and mechanical specifications of the MF-LR730. The 20V voltage rating of the LR4-730F is an uprated specification that maintains full compatibility with 10V-rated applications, as the component operates safely at voltages below its maximum rating.

Q: What is the significance of the voltage rating difference?

A: The MF-LR730 has a maximum voltage rating of 10V, while the LR4-730F is rated for 20V. In polymeric PTC resettable fuses, a higher voltage rating indicates enhanced dielectric capability. For applications designed for 10V operation, the 20V-rated LR4-730F provides additional safety margin without affecting the hold current, trip current, or response time characteristics.

Q: Are the physical dimensions compatible?

A: The components have similar but not identical dimensions. The MF-LR730 measures 1.163" L x 0.569" W (29.55mm x 14.45mm), while the LR4-730F measures 1.106" L x 0.559" W (28.10mm x 14.20mm). Both share the same maximum thickness of 0.039" (1.00mm) and strap package configuration. Verify PCB layout clearances before substitution.

Q: Do both parts meet the same regulatory standards?

A: Both components are ROHS3 compliant and REACH unaffected. The MF-LR730 carries cURus and TUV approvals, while the LR4-730F carries CSA, TUV, and UL approvals. The LR4-730F provides broader certification coverage suitable for applications requiring UL or CSA compliance.

Q: What is the inventory status for each part?

A: The MF-LR730 has 1,028 units in stock. The LR4-730F has 3,100 units in stock, providing greater availability for supply chain planning.

Q: Are the electrical characteristics identical?

A: Yes. Both components share identical specifications for hold current (7.3 A), trip current (14.1 A), time to trip (5 seconds), initial resistance (6 mOhms minimum), and post-trip resistance (15 mOhms maximum). Operating temperature range is identical at -40°C to 85°C.