FDC633N N-Channel MOSFET 30V 5.2A Equivalent & Substitute Parts

Part Overview

The FDC633N is an N-Channel MOSFET manufactured by onsemi, rated for 30V drain-to-source voltage with 5.2A continuous drain current at 25°C. The device is housed in a SuperSOT-6 surface mount package and is designed for general-purpose switching applications. The FDC633N is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Drain-to-Source Voltage (Vdss)	30	V
Continuous Drain Current (Id) @ 25°C	5.2	A
On-Resistance (Rds On) @ 5.2A, 4.5V	42	mOhm
Gate Threshold Voltage (Vgs(th)) @ 250µA	1	V
Gate Charge (Qg) @ 4.5V	16	nC
Power Dissipation (Max)	1.6	W
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-23-6 Thin (SuperSOT-6)	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitution of the FDC633N is determined by the following critical parameters:

Primary Substitution Criteria:

FET Type: N-Channel (required)
Drain-to-Source Voltage (Vdss): 30V minimum (required)
Continuous Drain Current (Id): 5.2A or greater (required for direct replacement)
On-Resistance (Rds On): Lower or equal values preferred for thermal performance
Operating Temperature Range: -55°C to 150°C (required)
Package Type: Surface mount configurations compatible with SOT-23-6 footprint or equivalent

Secondary Considerations:

Gate Charge (Qg): Lower values reduce switching losses
Power Dissipation: Higher ratings provide thermal margin
Product Status: Active status preferred for long-term availability

Substitute parts are grouped into two categories:

Category A – Direct Current Rating Matches or Exceeds (5.2A or higher): These parts maintain or exceed the 5.2A continuous drain current specification, providing equivalent or superior current handling capacity.

Category B – Reduced Current Rating (Below 5.2A): These parts operate below the 5.2A specification and are suitable only for applications where the actual circuit current requirement is lower than the FDC633N rating.

Parameter Comparison

Part Number	Manufacturer	FET Type	Vdss (V)	Id @ 25°C (A)	Rds On (mOhm)	Vgs(th) (V)	Qg (nC)	Power Diss. (W)	Package	Product Status
FDC633N	onsemi	N-Channel	30	5.2	42 @ 5.2A, 4.5V	1 @ 250µA	16 @ 4.5V	1.6	SOT-23-6 Thin	Obsolete
AO6400	Alpha & Omega Semiconductor	N-Channel	30	6.9	28 @ 6.9A, 10V	1.4 @ 250µA	12 @ 4.5V	2	SC-74, SOT-457	Not For New Designs
AO6424A	Alpha & Omega Semiconductor	N-Channel	30	6.5	35 @ 5A, 10V	2.4 @ 250µA	12 @ 10V	2.5	SC-74, SOT-457	Active
RSQ020N03TR	Rohm Semiconductor	N-Channel	30	2	134 @ 2A, 10V	2.5 @ 1mA	3.1 @ 5V	0.6	SOT-23-6 Thin	Active
RSQ045N03TR	Rohm Semiconductor	N-Channel	30	4.5	38 @ 4.5A, 10V	2.5 @ 1mA	9.5 @ 5V	0.6	SOT-23-6 Thin	Active
RTQ020N03TR	Rohm Semiconductor	N-Channel	30	2	125 @ 2A, 4.5V	1.5 @ 1mA	3.3 @ 4.5V	1.25	SOT-23-6 Thin	Active
RTQ035N03TR	Rohm Semiconductor	N-Channel	30	3.5	54 @ 3.5A, 4.5V	1.5 @ 1mA	6.4 @ 4.5V	1.25	SOT-23-6 Thin	Not For New Designs
RTQ045N03TR	Rohm Semiconductor	N-Channel	30	4.5	43 @ 4.5A, 4.5V	1.5 @ 1mA	10.7 @ 4.5V	1.25	SOT-23-6 Thin	Not For New Designs

Engineering Selection Recommendations

For Applications Requiring Full 5.2A Capacity:

AO6424A (Alpha & Omega Semiconductor) is the primary substitute. This device is rated for 6.5A continuous drain current, exceeding the FDC633N specification by 25%. The AO6424A carries Active product status, ensuring long-term availability and supply chain stability. The device is RoHS3 compliant and REACH unaffected. On-resistance of 35 mOhm at 5A, 10V is comparable to the FDC633N at 42 mOhm, with superior power dissipation rating of 2.5W. Package compatibility requires verification as the AO6424A uses SC-74/SOT-457 versus the FDC633N SuperSOT-6.

AO6400 (Alpha & Omega Semiconductor) provides an alternative with 6.9A rating and lower on-resistance of 28 mOhm. However, this device is classified as Not For New Designs, limiting its suitability for new product development.

For Applications with Reduced Current Requirements (Below 5.2A):

RTQ045N03TR (Rohm Semiconductor) is rated for 4.5A and maintains the SOT-23-6 Thin package footprint, ensuring direct PCB compatibility. This device is Active status and RoHS3 compliant. On-resistance of 43 mOhm at 4.5A, 4.5V closely matches the FDC633N specification. Power dissipation of 1.25W provides adequate thermal margin for most applications operating below 4.5A.

RSQ045N03TR (Rohm Semiconductor) offers 4.5A rating with 38 mOhm on-resistance at 4.5A, 10V. This device is Active status and maintains SOT-23-6 Thin package compatibility. Power dissipation of 0.6W is lower than the FDC633N, suitable for lower-power switching applications.

RTQ035N03TR (Rohm Semiconductor) is rated for 3.5A with 54 mOhm on-resistance. Although classified as Not For New Designs, this device maintains SOT-23-6 Thin package compatibility and is suitable for legacy system support.

For Lower Current Applications (Below 3.5A):

RTQ020N03TR and RSQ020N03TR are rated for 2A continuous drain current. Both maintain SOT-23-6 Thin package compatibility and Active product status. These devices are suitable only for applications where circuit current does not exceed 2A.

Compliance and Certification:

All recommended substitute parts are RoHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements. Moisture sensitivity level is 1 (Unlimited) across all substitutes, matching the FDC633N specification.

Frequently Asked Questions (FAQ)

Q: Can AO6424A directly replace FDC633N on the PCB?

A: Electrical substitution is valid; however, package compatibility must be verified. The FDC633N uses SuperSOT-6 (SOT-23-6 Thin), while AO6424A uses SC-74/SOT-457. Footprint differences may require PCB layout modification. Consult device datasheets for pin configuration and mechanical dimensions.

Q: What is the difference between RTQ045N03TR and RSQ045N03TR?

A: Both devices are rated for 4.5A at 30V and maintain SOT-23-6 Thin package compatibility. RTQ045N03TR has on-resistance of 43 mOhm at 4.5A, 4.5V with 1.25W power dissipation. RSQ045N03TR has on-resistance of 38 mOhm at 4.5A, 10V with 0.6W power dissipation. RTQ045N03TR is preferred for applications requiring higher power dissipation capability. Both are classified as Not For New Designs.

Q: Why is AO6400 listed as "Not For New Designs"?

A: Product status indicates manufacturer recommendation against use in new product development. While AO6400 remains available in inventory, long-term supply and support are not guaranteed. For new designs, AO6424A (Active status) is the preferred Alpha & Omega Semiconductor option.

Q: Can I use RTQ020N03TR in place of FDC633N?

A: RTQ020N03TR is rated for 2A continuous drain current, which is 62% below the FDC633N specification of 5.2A. This substitution is valid only if the actual circuit current requirement does not exceed 2A. Using RTQ020N03TR in a 5.2A application will result in device failure or thermal shutdown.

Q: What does "On-Resistance (Rds On)" mean for substitution?

A: On-resistance is the resistance between drain and source when the MOSFET is fully conducting. Lower on-resistance reduces power dissipation and heat generation. The FDC633N has 42 mOhm at 5.2A, 4.5V. Substitute parts with equal or lower on-resistance at equivalent current and gate voltage provide equivalent or superior performance.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed carry RoHS3 compliance certification. The FDC633N is not explicitly marked as RoHS3 compliant in the provided data. If RoHS3 compliance is a design requirement, all listed substitutes meet this criterion.

Q: What is the significance of Gate Charge (Qg)?

A: Gate charge determines the energy required to switch the MOSFET on and off. Lower gate charge reduces switching losses and allows faster switching speeds. The FDC633N has 16 nC at 4.5V. Substitutes with lower gate charge (such as AO6400 at 12 nC) provide improved switching efficiency.

Q: Can I use a substitute part rated for higher voltage than 30V?

A: The provided substitute list contains only 30V-rated devices. Using a higher-voltage MOSFET is electrically valid but may introduce unnecessary cost and size penalties. Voltage rating selection should match circuit requirements.

Q: What is the operating temperature range for all substitutes?

A: The FDC633N operates from -55°C to 150°C (TJ). Most substitutes maintain this range. RSQ020N03TR and RSQ045N03TR specify 150°C maximum without explicit lower limit in the provided data. Verify complete temperature specifications in device datasheets for applications requiring full -55°C to 150°C operation.

Q: Is package compatibility automatic between SOT-23-6 variants?

A: No. While multiple substitutes use SOT-23-6 Thin packaging, mechanical dimensions and pin configurations may vary. SuperSOT-6, TSMT6 (SC-95), and standard SOT-23-6 are distinct package variants. PCB footprint verification is mandatory before substitution.

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