RUSBF155-AP Polymeric PTC Resettable Fuse - Equivalent & Substitute Parts

Part Overview

The RUSBF155-AP is a polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® series. This component provides overcurrent protection with automatic reset capability in a through-hole radial disc package. The device is rated for 6V maximum voltage with a 1.55A hold current and 2.65A trip current. The part is currently active in production with 2683 units in stock. Substitute parts are identified when electrical parameters, mechanical form factor, and regulatory compliance remain equivalent across the specified operating conditions.

Key Parameters

Parameter	Value
Voltage - Max	6V
Current - Hold (Ih) (Max)	1.55 A
Current - Trip (It)	2.65 A
Current - Max	40 A
Time to Trip	2.2 s
Resistance - Initial (Ri) (Min)	40 mOhms
Resistance - Post Trip (R1) (Max)	100 mOhms
Operating Temperature Range	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.272" Dia x 0.122" T (6.90mm x 3.10mm)
Lead Spacing	0.201" (5.10mm)
RoHS Status	ROHS3 Compliant
Approval Agency	CSA, TUV, UL

Substitute Part Grouping Explanation

Substitution eligibility for the RUSBF155-AP is determined by strict equivalence across the following critical parameters:

Voltage rating: 6V maximum
Hold current (Ih): 1.55A maximum
Trip current (It): 2.65A
Maximum current capacity: 40A
Time to trip: 2.2 seconds
Initial resistance (Ri): 40 mOhms minimum
Post-trip resistance (R1): 100 mOhms maximum
Operating temperature range: -40°C to 85°C
Mounting configuration: Through hole radial disc
Physical dimensions: 0.272" diameter x 0.122" thickness (6.90mm x 3.10mm)
Lead spacing: 0.201" (5.10mm) nominal
Regulatory compliance: CSA, TUV, UL certification
RoHS compliance: ROHS3 standard

The RUSBF155-2 meets all substitution criteria as an equivalent part within the same PolySwitch® RUSBF series.

Parameter Comparison

Parameter	RUSBF155-AP	RUSBF155-2	Match Status
Voltage - Max	6V	6V	Equivalent
Current - Hold (Ih) (Max)	1.55 A	1.55 A	Equivalent
Current - Trip (It)	2.65 A	2.65 A	Equivalent
Current - Max	40 A	40 A	Equivalent
Time to Trip	2.2 s	2.2 s	Equivalent
Resistance - Initial (Ri) (Min)	40 mOhms	40 mOhms	Equivalent
Resistance - Post Trip (R1) (Max)	100 mOhms	100 mOhms	Equivalent
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	Equivalent
Mounting Type	Through Hole	Through Hole	Equivalent
Package / Case	Radial, Disc	Radial, Disc	Equivalent
Size / Dimension	0.272" Dia x 0.122" T (6.90mm x 3.10mm)	0.272" L x 0.122" W (6.90mm x 3.10mm)	Equivalent
Lead Spacing	0.201" (5.10mm)	0.200" (5.08mm)	Equivalent
Approval Agency	CSA, TUV, UL	CSA, TUV, UL	Equivalent
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Equivalent
Product Status	Active	Active	Equivalent

Engineering Selection Recommendations

Both the RUSBF155-AP and RUSBF155-2 are active production components from Littelfuse Inc. with identical electrical specifications and regulatory certifications. Selection between these parts is based on availability and packaging format. Both parts carry CSA, TUV, and UL approvals and meet ROHS3 compliance requirements. The lead spacing difference of 0.001" (0.02mm) between the two parts is within standard manufacturing tolerance and does not affect PCB footprint compatibility for through-hole applications. Component selection should prioritize inventory availability and delivery lead time, as electrical and mechanical performance are equivalent.

Frequently Asked Questions (FAQ)

Q: Can RUSBF155-2 be used as a direct replacement for RUSBF155-AP?

A: Yes. The RUSBF155-2 is electrically and mechanically equivalent to the RUSBF155-AP. All critical parameters including voltage rating, hold current, trip current, resistance characteristics, and operating temperature range are identical. Both parts are certified by CSA, TUV, and UL and comply with ROHS3 standards.

Q: What is the significance of the lead spacing difference (0.201" vs 0.200")?

A: The 0.001" (0.02mm) difference in lead spacing falls within standard manufacturing tolerance for through-hole radial components and does not require PCB redesign. Both parts are compatible with the same footprint specifications.

Q: Are there any differences in package format between these parts?

A: Both parts are supplied in cut tape (CT) packaging and feature identical radial disc form factors. The physical dimensions of 0.272" x 0.122" (6.90mm x 3.10mm) are equivalent for both parts.

Q: What regulatory certifications apply to both substitute parts?

A: Both the RUSBF155-AP and RUSBF155-2 carry approvals from CSA, TUV, and UL. Both parts comply with ROHS3 environmental standards.

Q: How do I determine which part to order?

A: Selection should be based on current inventory availability and delivery requirements. Since electrical performance and mechanical compatibility are identical, either part satisfies the same circuit protection requirements. Consult your supplier for stock levels and lead times.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message