FDS6670AS N-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The FDS6670AS is an N-Channel MOSFET manufactured by onsemi, rated for 30V drain-to-source voltage with 13.5A continuous drain current at 25°C. The device is housed in an 8-SOIC surface mount package and features PowerTrench® and SyncFET™ technology. The FDS6670AS is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	FDS6670AS	Unit
Drain-to-Source Voltage (Vdss)	30	V
Continuous Drain Current (Id) @ 25°C	13.5	A
On-Resistance (Rds On) @ 13.5A, 10V	9	mOhm
Gate Threshold Voltage (Vgs(th)) @ 1mA	3	V
Gate Charge (Qg) @ 10V	38	nC
Input Capacitance (Ciss) @ 15V	1540	pF
Power Dissipation (Max)	2.5	W
Operating Temperature Range	-55 to 150	°C
Package Type	8-SOIC	—
FET Type	N-Channel	—

Substitute Part Grouping Explanation

Substitution of the FDS6670AS is determined by the following critical parameters:

Electrical Compatibility Requirements:

Drain-to-Source Voltage (Vdss) must be equal to or greater than 30V
Continuous Drain Current (Id) must be equal to or greater than 13.5A
On-Resistance (Rds On) must be equal to or less than 9mOhm at rated current and 10V gate voltage
Gate Threshold Voltage (Vgs(th)) must be compatible with 10V drive voltage
Power Dissipation must support 2.5W minimum

Mechanical Compatibility Requirements:

Surface mount package type (8-SOIC or equivalent 8-pin surface mount)
Package footprint: 0.154" width, 3.90mm width standard
Mounting type: Surface Mount

Environmental Compatibility Requirements:

Operating temperature range must encompass -55°C to 150°C
RoHS3 compliance required
Moisture Sensitivity Level (MSL) of 1 or 3 acceptable

Substitute parts are grouped into two categories: direct equivalents (matching all critical parameters within tolerance) and functional alternatives (meeting electrical requirements with minor parameter variations).

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On @ 10V (mOhm)	Vgs(th) (V)	Qg @ 10V (nC)	Ciss @ 15V (pF)	Power Diss (W)	Temp Range (°C)	Package	Status
FDS6670AS	onsemi	30	13.5	9	3	38	1540	2.5	-55 to 150	8-SOIC	Obsolete
FDS8896	onsemi	30	15	6	2.5	67	2525	2.5	-55 to 150	8-SOIC	Active
IRF8721TRPBF	Infineon	30	14	8.5	2.35	12	1040	2.5	-55 to 150	8-SO	Active
IRF7821TRPBF	Infineon	30	13.6	9.1	1	14	1010	2.5	-55 to 155	8-SO	Active
AO4492	Alpha & Omega	30	14	9.5	2.2	18	770	3.1	-55 to 150	8-SOIC	Obsolete
DMN3010LSS-13	Diodes Inc.	30	16	9	2	43.7	2096	2.5	-55 to 150	8-SOP	Active
SI4174DY-T1-GE3	Vishay	30	17	9.5	2.2	27	985	2.5	-55 to 150	8-SOIC	Active
SI4686DY-T1-GE3	Vishay	30	18.2	9.5	3	26	1220	3	-55 to 150	8-SOIC	Active
RSS125N03TB	Rohm	30	12.5	8.9	2.5	28	1670	2	-55 to 150	8-SOP	Active
FDS4470	Fairchild	40	12.5	9	5	63	2659	2.5	-55 to 175	8-SOIC	Active
TSM180N03CS RLG	Taiwan Semi	30	9	18	2	14	345	2.5	-55 to 150	8-SOP	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents):

The FDS8896 from onsemi is the primary recommended substitute. It maintains the same 30V Vdss rating, exceeds the minimum 13.5A current requirement at 15A, and delivers superior on-resistance performance at 6mOhm. The device is manufactured by the same supplier, uses identical PowerTrench® technology, and is classified as Active. Both parts share the 8-SOIC package footprint and identical operating temperature range.

The IRF7821TRPBF from Infineon provides near-equivalent performance with 13.6A continuous drain current and 9.1mOhm on-resistance. This part is Active and meets all electrical requirements. The 8-SO package is mechanically compatible with the 8-SOIC footprint. Operating temperature extends to 155°C, exceeding the FDS6670AS specification.

Secondary Substitutes (Functional Alternatives):

The SI4174DY-T1-GE3 from Vishay Siliconix offers 17A continuous drain current with 9.5mOhm on-resistance, providing current margin above the 13.5A requirement. The TrenchFET® technology and Active status support long-term availability. The 8-SOIC package is directly compatible.

The DMN3010LSS-13 from Diodes Incorporated provides 16A continuous drain current with 9mOhm on-resistance, matching the FDS6670AS on-resistance specification. The device is Active and housed in an 8-SOP package compatible with the 8-SOIC footprint.

Marginal Substitutes (Limited Compatibility):

The RSS125N03TB from Rohm Semiconductor delivers 12.5A continuous drain current, which falls below the FDS6670AS 13.5A specification. This part is suitable only for applications where the actual operating current does not exceed 12.5A. The 8.9mOhm on-resistance is acceptable, and the device is Active.

The TSM180N03CS RLG from Taiwan Semiconductor Corporation provides only 9A continuous drain current, significantly below the FDS6670AS rating. This part is not suitable for direct substitution in applications requiring the full 13.5A capability.

Not Recommended:

The FDS4470 from Fairchild Semiconductor, while Active, operates at 40V Vdss, which exceeds the FDS6670AS specification. This higher voltage rating introduces unnecessary design complexity and cost. The 12.5A current rating also falls below the FDS6670AS requirement.

The AO4492 from Alpha & Omega Semiconductor is classified as Obsolete, eliminating the procurement advantage over the FDS6670AS itself.

Frequently Asked Questions (FAQ)

Q: Can the FDS8896 directly replace the FDS6670AS in existing designs?

A: Yes. The FDS8896 maintains the same 30V Vdss rating, 8-SOIC package footprint, and operating temperature range. The 15A continuous drain current exceeds the FDS6670AS 13.5A specification, and the 6mOhm on-resistance is superior. No circuit modifications are required.

Q: What is the difference between 8-SOIC and 8-SO packages?

A: Both designations refer to 8-pin surface mount packages with identical 0.154" (3.90mm) width and pin spacing. The packages are mechanically and electrically interchangeable. Differences in naming convention reflect manufacturer terminology rather than physical incompatibility.

Q: Why does the FDS4470 have a higher Vdss rating than the FDS6670AS?

A: The FDS4470 is rated for 40V Vdss compared to the FDS6670AS 30V rating. Higher voltage ratings do not provide functional advantages in 30V applications and typically result in increased on-resistance and gate charge. The FDS4470 is not recommended as a substitute.

Q: Is the IRF7821TRPBF suitable for applications requiring the full 13.5A continuous current?

A: Yes. The IRF7821TRPBF is rated for 13.6A continuous drain current, which meets the FDS6670AS requirement. The 9.1mOhm on-resistance is within acceptable tolerance of the FDS6670AS 9mOhm specification.

Q: What does "Obsolete" product status mean for the FDS6670AS?

A: Obsolete status indicates that the manufacturer has discontinued production and will not accept new orders. Existing inventory may be available through authorized distributors, but long-term procurement is not guaranteed. Active substitute parts ensure design continuity and future availability.

Q: Can the TSM180N03CS RLG replace the FDS6670AS?

A: No. The TSM180N03CS RLG is rated for only 9A continuous drain current, which is significantly below the FDS6670AS 13.5A specification. This part is suitable only for applications with lower current requirements.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed in this reference are RoHS3 compliant, matching the FDS6670AS compliance status. Moisture Sensitivity Level (MSL) ratings are either 1 (Unlimited) or 3 (168 Hours), both acceptable for standard surface mount assembly processes.

Q: What is the significance of gate charge (Qg) differences between substitute parts?

A: Gate charge affects switching speed and driver circuit requirements. The FDS6670AS specifies 38nC at 10V. Substitute parts with lower gate charge (such as IRF7821TRPBF at 14nC) enable faster switching and reduce driver power dissipation. Higher gate charge values require more robust gate drive circuits but do not prevent substitution.

Q: Which substitute part offers the best on-resistance performance?

A: The FDS8896 delivers the lowest on-resistance at 6mOhm, compared to the FDS6670AS 9mOhm specification. This superior performance reduces power dissipation and heat generation in switching applications.

Q: Can substitute parts with higher power dissipation ratings be used in place of the FDS6670AS?

A: Yes. Parts with higher power dissipation ratings (such as AO4492 at 3.1W or SI4686DY-T1-GE3 at 3W) are fully compatible with the FDS6670AS 2.5W specification. Higher ratings provide additional thermal margin and do not affect circuit operation.

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