RUSBF090 Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The RUSBF090 is a polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® series. This component provides overcurrent protection with automatic reset capability in through-hole radial configuration. The part is active in production and widely used in circuit protection applications requiring 16V maximum voltage rating and 900 mA hold current specification. Substitute parts are identified when equivalent electrical and mechanical parameters align with application requirements, enabling component sourcing flexibility and inventory optimization.

Substiute Parts

RUSBF090

Littelfuse Inc.In Stock: 1434RUSBF090 Datasheet

Current PartRFQ

MF-R090-0-9

Bourns Inc.In Stock: 3246MF-R090-0-9 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the RUSBF090 is determined by the following critical parameters:

• Current - Hold (Ih) (Max): Must match at 900 mA to ensure equivalent protection threshold
• Current - Trip (It): Must match at 1.8 A to maintain consistent trip behavior
• Mounting Type: Must be Through Hole to ensure PCB compatibility
• Package / Case: Must be Radial, Disc configuration for mechanical fit
• Operating Temperature Range: Must support -40°C ~ 85°C minimum
• RoHS Compliance: Must meet ROHS3 standard for regulatory alignment

The MF-R090-0-9 from Bourns Inc. meets these core substitution criteria. Voltage rating differences (30V vs. 16V) do not preclude substitution, as higher voltage-rated components operate safely in lower-voltage applications. Physical dimensions remain compatible within specified tolerances.

Parameter Comparison

Engineering Selection Recommendations

Both the RUSBF090 and MF-R090-0-9 are active production components with ROHS3 compliance and equivalent regulatory certifications (CSA, TUV, UL for RUSBF090; cURus, TUV for MF-R090-0-9). Selection between these parts should be based on:

• Inventory availability: MF-R090-0-9 currently has 3210 units in stock versus 1385 units for RUSBF090
• Voltage margin requirements: MF-R090-0-9 provides 30V rating, offering additional voltage headroom in applications where circuit voltage may exceed 16V nominal
• Post-trip resistance tolerance: RUSBF090 specifies 180 mOhms maximum versus 220 mOhms for MF-R090-0-9; applications sensitive to post-trip resistance should verify compatibility
• Packaging format: RUSBF090 is supplied in Bag packaging; MF-R090-0-9 is supplied in Bulk packaging

Both components satisfy the core electrical and mechanical requirements for direct substitution in 16V, 900 mA hold current applications.

Frequently Asked Questions (FAQ)

Q: Can MF-R090-0-9 replace RUSBF090 in a 16V circuit?

A: Yes. The MF-R090-0-9 is rated for 30V maximum, which exceeds the 16V circuit requirement. All critical parameters—hold current (900 mA), trip current (1.8 A), initial resistance (70 mOhms), and operating temperature range (-40°C ~ 85°C)—are identical. Physical dimensions and lead spacing are compatible within tolerance.

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

A: The MF-R090-0-9 30V rating indicates the component can safely operate at voltages up to 30V. In a 16V application, this provides additional voltage margin without affecting protection characteristics. The hold current and trip current thresholds remain unchanged.

Q: Are there mechanical compatibility concerns?

A: No. Both components use Through Hole, Radial Disc packaging with nearly identical dimensions (7.40mm diameter, 3.10mm vs. 3.00mm thickness) and lead spacing (5.05mm vs. 5.10mm). These minor variations fall within standard PCB design tolerances.

Q: Does post-trip resistance difference affect substitution?

A: The MF-R090-0-9 specifies 220 mOhms maximum post-trip resistance versus 180 mOhms for RUSBF090. Applications where post-trip resistance is a critical design parameter should evaluate this 40 mOhms difference against circuit requirements.

Q: Are both parts RoHS compliant?

A: Yes. Both RUSBF090 and MF-R090-0-9 are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards.