06R120BPR Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The 06R120BPR is a polymeric PTC resettable fuse manufactured by Littelfuse Inc., rated for 6V maximum voltage with 1.2A hold current. This component is designed for overcurrent protection in electronic circuits with automatic reset capability after fault condition removal. The part is currently classified as obsolete, making identification of compatible substitute components essential for ongoing design support, maintenance, and production continuity.

Key Parameters

Parameter	Value
Voltage - Max	6V
Current - Hold (Ih) (Max)	1.2 A
Current - Trip (It)	2 A
Current - Max	40 A
Time to Trip	500 ms
Resistance - Initial (Ri) (Min)	65 mOhms
Resistance - Post Trip (R1) (Max)	140 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 06R120BPR is determined by strict equivalence across the following critical parameters:

Voltage rating: 6V maximum
Current hold specification: 1.2A maximum
Current trip threshold: 2A
Maximum current capacity: 40A
Time to trip response: 500 milliseconds
Operating temperature range: -40°C to 85°C
Mounting configuration: Through hole radial disc package
Lead spacing tolerance: 0.201" ± acceptable mechanical variation

The RUSBF120-2 meets all specified electrical and mechanical criteria for direct substitution. Both components are polymeric PTC resettable fuses with identical functional ratings and environmental specifications.

Parameter Comparison

Parameter	06R120BPR	RUSBF120-2	Match Status
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Identical
Type	Polymeric	Polymeric	Identical
Voltage - Max	6V	6V	Identical
Current - Hold (Ih) (Max)	1.2 A	1.2 A	Identical
Current - Trip (It)	2 A	2 A	Identical
Current - Max	40 A	40 A	Identical
Time to Trip	500 ms	500 ms	Identical
Resistance - Initial (Ri) (Min)	65 mOhms	70 mOhms	Within tolerance
Resistance - Post Trip (R1) (Max)	140 mOhms	140 mOhms	Identical
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	Identical
Mounting Type	Through Hole	Through Hole	Identical
Package / Case	Radial, Disc	Radial, Disc	Identical
Lead Spacing	0.201" (5.10mm)	0.200" (5.08mm)	Within tolerance
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Identical
Product Status	Obsolete	Active	Substitute is active

Engineering Selection Recommendations

The RUSBF120-2 is the qualified substitute for the obsolete 06R120BPR. Selection rationale is based on the following factors:

Electrical Equivalence: All critical electrical parameters match specification, including voltage rating, hold current, trip current, maximum current capacity, and response time. Initial resistance variance (70 mOhms vs. 65 mOhms minimum) remains within acceptable operational tolerance for polymeric PTC fuse applications.

Mechanical Compatibility: Both components utilize identical through-hole radial disc packaging with lead spacing within 0.02mm variance (5.08mm vs. 5.10mm), ensuring direct PCB footprint compatibility without layout modification.

Regulatory Compliance: The RUSBF120-2 maintains ROHS3 compliance and carries expanded approval certifications (CSA, TUV, UL) compared to the original part (cURus, TUV), providing enhanced regulatory coverage for new designs and production environments.

Product Status: The RUSBF120-2 is actively manufactured and stocked (3990 units available), ensuring supply chain continuity and long-term availability for production requirements.

Frequently Asked Questions (FAQ)

Q: Can the RUSBF120-2 be used as a direct replacement for the 06R120BPR in existing designs?

A: Yes. The RUSBF120-2 meets all electrical and mechanical specifications for direct substitution. PCB footprint compatibility is maintained, and no circuit redesign is required.

Q: What is the significance of the initial resistance difference (65 mOhms vs. 70 mOhms)?

A: The 5 mOhms variance falls within normal manufacturing tolerance for polymeric PTC fuses and does not affect circuit protection performance or thermal characteristics in typical applications.

Q: Are there packaging differences between these parts?

A: The 06R120BPR is supplied in standard packaging, while the RUSBF120-2 is available in cut tape format. Both maintain identical component geometry and through-hole radial configuration. Tape packaging does not affect component electrical or mechanical properties.

Q: What certifications does the RUSBF120-2 carry?

A: The RUSBF120-2 holds CSA, TUV, and UL approvals, providing broader regulatory acceptance than the original 06R120BPR (cURus, TUV).

Q: Is the lead spacing difference (5.10mm vs. 5.08mm) a concern for PCB assembly?

A: No. The 0.02mm variance is within standard PCB tolerance and does not affect insertion or soldering operations on standard through-hole assembly equipment.

Q: Why is the 06R120BPR classified as obsolete?

A: Obsolescence reflects manufacturer discontinuation. The RUSBF120-2 represents the active production equivalent within the Littelfuse polymeric PTC fuse product line.

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