LR4-450F Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The LR4-450F is an active polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® LR4 series. This component provides overcurrent protection with a 20V maximum voltage rating and 4.5A hold current specification. The device is designed for strap mounting applications and operates across the -40°C to 85°C temperature range.

Substitute parts are identified when equivalent electrical performance can be maintained across critical parameters including voltage rating, hold current, trip current, resistance characteristics, and physical form factor compatibility.

Substiute Parts

LR4-450F

Littelfuse Inc.In Stock: 973LR4-450F Datasheet

Current PartRFQ

0ZSC0450FF1E

Bel Fuse Inc.In Stock: 8000ZSC0450FF1E Datasheet

DirectRFQ

MF-LR450

Bourns Inc.In Stock: 2156MF-LR450 Datasheet

DirectRFQ

MF-LR730/20-0

Bourns Inc.In Stock: 5269MF-LR730/20-0 Datasheet

MFR RecommendedRFQ

MF-LR900/20-0

Bourns Inc.In Stock: 1730MF-LR900/20-0 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts are classified based on electrical parameter equivalence and mechanical compatibility:

Direct Electrical Equivalent (0ZSC0450FF1E): Maintains identical voltage (20V), hold current (4.5A), trip current (8.9A), and resistance specifications. Physical dimensions vary slightly (0.402" W vs 0.413" W) but remain compatible with strap mounting applications. Manufactured by Bel Fuse Inc. under the 0ZSC series.

Voltage-Reduced Equivalent (MF-LR450): Provides matching hold current (4.5A) and trip current (8.9A) with identical resistance characteristics. Maximum voltage rating is 16V, representing a reduction from the 20V specification of the main part. Manufactured by Bourns Inc. under the Multifuse® MF-LR series. This part is suitable only for applications with maximum operating voltages of 16V or lower.

Higher Current Capacity Alternatives (MF-LR730/20-0, MF-LR900/20-0): These Bourns Multifuse® parts maintain the 20V voltage rating but provide elevated hold current ratings (7.3A and 9A respectively) with correspondingly higher trip currents. Physical dimensions increase to accommodate higher current capacity. These parts are suitable for applications requiring higher current protection thresholds while maintaining 20V voltage compatibility.

Parameter Comparison

Engineering Selection Recommendations

0ZSC0450FF1E (Bel Fuse Inc.): This part provides direct electrical equivalence to the LR4-450F with identical voltage, current, and resistance specifications. Both components maintain ROHS3 compliance and operate across the same temperature range. Selection of this substitute is appropriate when Bel Fuse sourcing is preferred or when Littelfuse supply is constrained. Approval agencies differ (cURus/TUV vs CSA/TUV/UL), requiring verification against application certification requirements.

MF-LR450 (Bourns Inc.): This Multifuse® part matches the hold current and trip current specifications of the LR4-450F but operates at a reduced maximum voltage of 16V. This substitute is suitable only for applications with circuit voltages not exceeding 16V. The lower voltage rating restricts its use to specific design scenarios. ROHS3 compliance and temperature range equivalence are maintained.

MF-LR730/20-0 and MF-LR900/20-0 (Bourns Inc.): These parts maintain the 20V voltage rating and ROHS3 compliance but provide higher hold current ratings (7.3A and 9A respectively). These substitutes are appropriate for applications requiring elevated overcurrent protection thresholds. Lower initial and post-trip resistance values (6 mOhms and 14-15 mOhms) result in reduced voltage drop characteristics. Physical dimensions increase to accommodate higher current capacity.

Frequently Asked Questions (FAQ)

Q: Can 0ZSC0450FF1E be used as a direct replacement for LR4-450F?

A: Yes. The 0ZSC0450FF1E maintains identical electrical specifications including 20V voltage rating, 4.5A hold current, 8.9A trip current, and matching resistance characteristics. Physical dimensions are compatible with strap mounting. Approval agency differences (cURus/TUV vs CSA/TUV/UL) should be evaluated against application requirements.

Q: Is MF-LR450 compatible with 20V circuits?

A: No. The MF-LR450 has a maximum voltage rating of 16V. This part is suitable only for applications with circuit voltages of 16V or lower. Use of this part in 20V circuits exceeds its voltage specification.

Q: When should MF-LR730/20-0 or MF-LR900/20-0 be selected?

A: These parts are selected when the application requires higher overcurrent protection thresholds than the 4.5A hold current of the LR4-450F. The MF-LR730/20-0 provides 7.3A hold current protection, while the MF-LR900/20-0 provides 9A hold current protection. Both maintain 20V voltage compatibility. Physical dimensions are larger to accommodate higher current capacity.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. The LR4-450F and all listed substitute parts (0ZSC0450FF1E, MF-LR450, MF-LR730/20-0, MF-LR900/20-0) are ROHS3 compliant.

Q: What is the impact of different approval agencies on part selection?

A: The LR4-450F carries CSA, TUV, and UL approvals. The Bel Fuse and Bourns substitutes carry cURus and TUV approvals. Application certification requirements determine whether approval agency differences affect part selection. Consult application specifications and regulatory requirements.

Q: Do all parts operate across the same temperature range?

A: Yes. All listed parts operate across the -40°C to 85°C temperature range.

Q: How do physical dimensions differ among substitute parts?

A: The 0ZSC0450FF1E maintains nearly identical dimensions to the LR4-450F (0.402" W vs 0.413" W). The MF-LR450 has similar dimensions (0.402" W). The MF-LR730/20-0 and MF-LR900/20-0 have larger dimensions (1.106" L x 0.559" W and 1.831" L x 0.323" W respectively) to accommodate higher current capacity. All parts maintain strap mounting compatibility.