FDMB668P P-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The FDMB668P is a P-Channel MOSFET manufactured by onsemi, rated for 20V drain-to-source voltage with 6.1A continuous drain current at 25°C. This device is housed in an 8-MLP MicroFET surface mount package and is part of the PowerTrench® series. The FDMB668P is classified as obsolete, making identification of functionally equivalent substitute components necessary for ongoing design support, production continuity, and component sourcing.

Substiute Parts

FDMB668P

onsemiIn Stock: 1158FDMB668P Datasheet

Current PartRFQ

PMPB33XP,115

NXP USA Inc.In Stock: 32251PMPB33XP,115 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the FDMB668P is determined by strict equivalence across the following critical electrical and mechanical parameters:

Electrical Equivalence Criteria:

• FET Type: P-Channel topology required
• Drain to Source Voltage (Vdss): Minimum 20V rating
• Continuous Drain Current (Id): Minimum 6.1A at 25°C ambient temperature
• On-State Resistance (Rds On): Maximum 35mOhm at rated current and gate voltage
• Power Dissipation: Minimum 1.9W at ambient temperature
• Operating Temperature Range: Full -55°C to 150°C capability

Mechanical Equivalence Criteria:

• Mounting Type: Surface Mount only
• Package Classification: Compatible with 8-pin or smaller pin-count configurations
• Thermal Performance: Adequate for 1.9W dissipation minimum

The PMPB33XP,115 substitute part meets these criteria with equivalent or superior electrical ratings while maintaining surface mount compatibility. The substitute part is classified as Active product status, ensuring ongoing availability and manufacturing support.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The FDMB668P is classified as obsolete. The PMPB33XP,115 is classified as Active, ensuring continued manufacturing support, availability, and compliance with current industry standards.

Compliance and Certification: Both parts carry identical ECCN (EAR99) and HTSUS (8541.29.0095) classifications, confirming regulatory equivalence for export and tariff purposes.

Electrical Performance: The PMPB33XP,115 substitute provides equivalent voltage rating (20V Vdss) and comparable on-state resistance characteristics. The substitute exhibits lower gate charge and input capacitance, resulting in reduced gate drive power requirements and faster switching transients. The continuous drain current rating of the substitute (5.5A) is lower than the original part (6.1A); applications requiring the full 6.1A rating must evaluate whether the 5.5A substitute meets circuit requirements.

Thermal Performance: The PMPB33XP,115 offers superior thermal performance at case temperature (Tc), rated at 12.5W versus the original part's 1.9W ambient temperature rating. This enhanced thermal capability supports higher power dissipation in thermally managed applications.

Package Consideration: The substitute part uses a 6-pin XFDFN package with exposed pad, compared to the original 8-pin MicroFET package. PCB layout redesign is required for substitution, including trace routing and thermal management modifications.

Frequently Asked Questions (FAQ)

Q: Can the PMPB33XP,115 directly replace the FDMB668P without PCB modification?

A: No. The PMPB33XP,115 uses a 6-XFDFN package with exposed pad, while the FDMB668P uses an 8-PowerWDFN package. Pin count and footprint differ, requiring PCB layout redesign. Thermal pad placement and trace routing must be updated to accommodate the new package geometry.

Q: What is the impact of the lower continuous drain current rating on the substitute part?

A: The PMPB33XP,115 is rated for 5.5A continuous drain current at 25°C, compared to 6.1A for the FDMB668P. Applications operating at or below 5.5A drain current experience no functional impact. Circuits requiring sustained currents above 5.5A must evaluate whether the substitute meets thermal and electrical requirements under actual operating conditions.

Q: Are the on-state resistance characteristics compatible?

A: Yes. The PMPB33XP,115 exhibits 37mOhm maximum on-state resistance at 5.5A and 4.5V gate voltage, compared to 35mOhm for the FDMB668P at 6.1A and 4.5V. The difference of 2mOhm is negligible for most applications. At equivalent current levels, the substitute provides comparable conduction losses.

Q: Does the substitute part offer any performance advantages?

A: The PMPB33XP,115 provides lower gate charge (23nC versus 59nC) and lower input capacitance (1575pF versus 2085pF), reducing gate drive power and enabling faster switching response. The substitute also supports higher maximum gate voltage (±12V versus ±8V) and offers superior thermal performance at case temperature (12.5W versus 1.9W).

Q: What is the significance of the different package types?

A: The 8-PowerWDFN package of the original part differs from the 6-XFDFN package of the substitute in pin count, footprint dimensions, and thermal pad configuration. Substitution requires complete PCB redesign, including component placement, trace routing, and thermal management strategy. The exposed pad on the substitute part improves thermal dissipation when properly connected to ground planes.

Q: Are both parts compliant with the same regulatory standards?

A: Yes. Both the FDMB668P and PMPB33XP,115 carry identical ECCN (EAR99) and HTSUS (8541.29.0095) classifications, confirming regulatory equivalence for export control and tariff purposes.

Q: Why is the original part classified as obsolete?

A: The FDMB668P is no longer in active production. The PMPB33XP,115, classified as Active, represents the current manufacturing alternative with equivalent or superior electrical characteristics and ongoing supplier support.