RUSBF250-AP Equivalent & Substitute Parts

Part Overview

The RUSBF250-AP is a polymeric PTC resettable fuse manufactured by Littelfuse, part of the PolySwitch® RUSBF series. This component provides overcurrent protection with a 16V maximum voltage rating and 2.5A hold current in a through-hole radial disc package. The RUSBF250-AP is currently listed as obsolete, making identification of active equivalent parts essential for ongoing production and maintenance applications.

Key Parameters

Parameter	Value
Voltage - Max	16V
Current - Hold (Ih) (Max)	2.5 A
Current - Trip (It)	5 A
Current - Max	40 A
Time to Trip	40 s
Resistance - Initial (Ri) (Min)	20 mOhms
Resistance - Post Trip (R1) (Max)	60 mOhms
Operating Temperature	-40°C ~ 85°C
Mounting Type	Through Hole
Package / Case	Radial, Disc
Size / Dimension	0.449" L x 0.118" W (11.40mm x 3.00mm)
Height - Seated (Max)	0.720" (18.30mm)
Lead Spacing	0.199" (5.05mm)
Approval Agency	CSA, TUV, UL
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

The RUSBF250-2 qualifies as a direct substitute for the RUSBF250-AP based on the following critical parameters:

Identical voltage rating: 16V maximum
Identical hold current: 2.5A
Identical trip current: 5A
Identical maximum current: 40A
Identical time to trip: 40 seconds
Identical initial resistance: 20 mOhms minimum
Identical post-trip resistance: 60 mOhms maximum
Identical operating temperature range: -40°C to 85°C
Identical mounting type: Through Hole
Identical package type: Radial, Disc
Identical physical dimensions: 11.40mm x 3.00mm
Identical seated height: 18.30mm
Identical regulatory approvals: CSA, TUV, UL
Identical RoHS compliance: ROHS3 Compliant

The primary distinction is product status: RUSBF250-AP is obsolete, while RUSBF250-2 is active. The RUSBF250-2 is available in Cut Tape (CT) packaging with higher inventory availability.

Parameter Comparison

Parameter	RUSBF250-AP	RUSBF250-2
Manufacturer	Littelfuse	Littelfuse Inc.
Series	PolySwitch®, RUSBF	PolySwitch®, RUSBF
Product Status	Obsolete	Active
Type	Polymeric	Polymeric
Voltage - Max	16V	16V
Current - Hold (Ih) (Max)	2.5 A	2.5 A
Current - Trip (It)	5 A	5 A
Current - Max	40 A	40 A
Time to Trip	40 s	40 s
Resistance - Initial (Ri) (Min)	20 mOhms	20 mOhms
Resistance - Post Trip (R1) (Max)	60 mOhms	60 mOhms
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Through Hole	Through Hole
Package / Case	Radial, Disc	Radial, Disc
Size / Dimension	0.449" L x 0.118" W (11.40mm x 3.00mm)	0.449" L x 0.118" W (11.40mm x 3.00mm)
Height - Seated (Max)	0.720" (18.30mm)	0.720" (18.30mm)
Lead Spacing	0.199" (5.05mm)	0.118" (3.00mm)
Approval Agency	CSA, TUV, UL	CSA, TUV, UL
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Packaging Type	-	Cut Tape (CT)
Inventory Status	1029 Pcs New Original In Stock	4092 Pcs New Original In Stock

Engineering Selection Recommendations

The RUSBF250-2 is the direct active equivalent for the obsolete RUSBF250-AP. Both components maintain identical electrical and thermal specifications, with full compatibility in overcurrent protection applications requiring 16V, 2.5A hold current operation.

Selection of RUSBF250-2 is supported by:

Active product status ensuring continued availability and manufacturer support
Identical regulatory certifications: CSA, TUV, UL approvals
ROHS3 compliance maintained across both parts
Higher inventory availability (4092 units versus 1029 units)
Identical mechanical and electrical performance characteristics

The lead spacing difference (0.199" versus 0.118") reflects packaging variation and does not affect functional substitution for through-hole radial disc applications.

Frequently Asked Questions (FAQ)

Q: Can RUSBF250-2 directly replace RUSBF250-AP in existing designs?

A: Yes. The RUSBF250-2 provides identical electrical performance, thermal characteristics, and regulatory compliance. Both components are polymeric PTC resettable fuses with matching voltage, current, and resistance specifications.

Q: What is the significance of the lead spacing difference?

A: Lead spacing (0.199" for RUSBF250-AP versus 0.118" for RUSBF250-2) reflects the physical lead configuration in the radial disc package. This difference does not affect electrical function or overcurrent protection performance. PCB layout compatibility should be verified for specific applications.

Q: Why is RUSBF250-AP listed as obsolete?

A: Product obsolescence indicates the manufacturer has discontinued production. The RUSBF250-2 represents the active equivalent, ensuring access to current inventory and ongoing manufacturer support.

Q: Are regulatory approvals identical between the two parts?

A: Yes. Both RUSBF250-AP and RUSBF250-2 carry identical approvals: CSA, TUV, and UL certifications. Both maintain ROHS3 compliance.

Q: What packaging formats are available?

A: RUSBF250-AP packaging format is not specified in available data. RUSBF250-2 is supplied in Cut Tape (CT) packaging, suitable for automated assembly processes.

Q: Are there any thermal or environmental differences?

A: No. Both components operate across the identical temperature range of -40°C to 85°C with matching thermal and environmental specifications.

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