Equivalent & Substitute Parts for MF-R400-AP-99

Part Overview

The MF-R400-AP-99 is a polymeric PTC resettable fuse manufactured by Bourns Inc. in the Multifuse® MF-R series. This component provides overcurrent protection at 30V with a 4A hold current rating and is designed for through-hole radial mounting applications. The part is currently listed as obsolete, making identification of active equivalent alternatives essential for ongoing production and maintenance requirements.

Substiute Parts

MF-R400-AP-99

Bourns Inc.In Stock: 929MF-R400-AP-99 Datasheet

Current PartRFQ

MF-R400-AP

Bourns Inc.In Stock: 1250MF-R400-AP Datasheet

Parametric EquivalentRFQ

30R400UMR

Littelfuse Inc.In Stock: 814730R400UMR Datasheet

DirectRFQ

RUEF400-AP

LittelfuseIn Stock: 1101RUEF400-AP Datasheet

DirectRFQ

RUEF400K-AP

Littelfuse Inc.In Stock: 1845RUEF400K-AP Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MF-R400-AP-99 is determined by strict equivalence across the following critical parameters:

• Voltage rating: 30V maximum
• Hold current (Ih): 4A maximum
• Trip current (It): 8A
• Initial resistance (Ri): 10 mOhms minimum
• Post-trip resistance (R1): 50 mOhms maximum
• Operating temperature range: -40°C to 85°C
• Mounting configuration: Through-hole radial
• Lead spacing: 0.201" (5.10mm) nominal tolerance
• Time to trip: 12.7 seconds
• Package type: Radial disc configuration

All identified substitute parts meet these core electrical and mechanical parameters. Variations in physical dimensions (length and height) remain within acceptable tolerances for through-hole radial mounting applications. Differences in approval agencies and maximum current ratings above the specified hold current do not affect substitution validity.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: MF-R400-AP (Bourns Inc.)

The MF-R400-AP is the direct parametric equivalent from the original manufacturer. This part maintains identical electrical specifications and is currently in active production status. It provides the most direct replacement path with no design modifications required. Packaging is supplied in Tape & Box (TB) format with 1184 units in stock.

Secondary Recommendations: 30R400UMR, RUEF400-AP, RUEF400K-AP (Littelfuse Inc.)

All three Littelfuse alternatives meet the complete electrical and mechanical specification requirements. These parts are active production items with substantial inventory availability (8046, 1085, and 1742 units respectively). The RUEF series components feature expanded approval agency certifications (CQC, CSA, TUV, UL) compared to the original Bourns part. Lead spacing tolerance on RUEF variants is 0.199" (5.05mm), which remains within acceptable through-hole mounting tolerances. Physical dimension variations (length and height) do not impact circuit board layout compatibility for radial disc configurations.

All substitute parts carry ROHS3 compliance and REACH unaffected status, meeting current regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can MF-R400-AP-99 be directly replaced with MF-R400-AP?

A: Yes. The MF-R400-AP is the active production equivalent from Bourns Inc. with identical electrical parameters, operating temperature range, and mounting configuration. No circuit modifications are required.

Q: What is the difference between Bourns and Littelfuse alternatives?

A: All alternatives meet the core electrical specifications (30V, 4A hold current, 8A trip current, 12.7s trip time). Littelfuse parts offer additional approval certifications. Physical dimensions vary slightly but remain compatible with through-hole radial mounting. Lead spacing tolerance differences (0.201" vs 0.199") are within acceptable PCB hole spacing tolerances.

Q: Are there differences in the RUEF400-AP and RUEF400K-AP variants?

A: Both RUEF variants are electrically identical with matching 30V, 4A, and 8A specifications. The primary difference is physical height (19.30mm vs 21.30mm seated height). Both are suitable for through-hole radial applications. Selection depends on available PCB clearance.

Q: What packaging formats are available?

A: MF-R400-AP is supplied in Tape & Box (TB). Littelfuse alternatives (30R400UMR, RUEF400-AP, RUEF400K-AP) are supplied in Cut Tape (CT) format. Both formats are compatible with standard component placement and assembly processes.

Q: Are all substitutes RoHS and REACH compliant?

A: Yes. All identified alternatives carry ROHS3 compliance and REACH unaffected status, meeting current regulatory requirements for electronic component procurement.

Q: Can lead spacing tolerance differences affect PCB compatibility?

A: Lead spacing on the original part is 0.201" (5.10mm). Littelfuse RUEF variants specify 0.199" (5.05mm). This 0.002" difference is within standard PCB hole tolerance specifications and does not require design modifications for radial disc through-hole mounting.