FDS6680AS Equivalent & Substitute Parts

Part Overview

The FDS6680AS is an N-Channel MOSFET manufactured by onsemi, rated for 30V drain-to-source voltage with 11.5A continuous drain current at 25°C. The device is housed in an 8-SOIC surface mount package and features PowerTrench® and SyncFET™ technology. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The FDS6680AS delivers 2.5W maximum power dissipation and operates across a temperature range of -55°C to 150°C (junction temperature).

Key Parameters

Parameter	FDS6680AS
Drain-to-Source Voltage (Vdss)	30 V
Continuous Drain Current (Id) @ 25°C	11.5 A
On-Resistance (Rds On) @ Id, Vgs	10 mOhm @ 11.5A, 10V
Gate Threshold Voltage (Vgs(th)) @ Id	3 V @ 1 mA
Gate Charge (Qg) @ Vgs	30 nC @ 10 V
Input Capacitance (Ciss) @ Vds	1240 pF @ 15 V
Power Dissipation (Max)	2.5 W
Operating Temperature Range	-55°C to 150°C (TJ)
Package Type	8-SOIC
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the FDS6680AS is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Drain-to-Source Voltage (Vdss) must equal or exceed 30V
Continuous Drain Current (Id) must meet or exceed 11.5A at 25°C
On-Resistance (Rds On) must not exceed 10 mOhm at rated current and gate voltage
Power Dissipation capability must support 2.5W minimum
Gate drive voltage compatibility (4.5V and 10V operation)
Operating temperature range must encompass -55°C to 150°C

Mechanical Compatibility Criteria:

Surface mount package type: 8-SOIC or equivalent footprint
Package dimensions: 0.154" width, 3.90mm width standard

The substitute parts listed below satisfy these criteria within the allowed parameter ranges specified for N-Channel MOSFET technology.

Parameter Comparison

Parameter	FDS6680AS (onsemi)	FDS4470 (Fairchild)	IRF7821TRPBF (Infineon)	TSM180N03CS RLG (Taiwan Semiconductor)
Vdss (V)	30	40	30	30
Id @ 25°C (A)	11.5	12.5	13.6	9
Rds On (mOhm) @ Id, Vgs	10 @ 11.5A, 10V	9 @ 12.5A, 10V	9.1 @ 13A, 10V	18 @ 8A, 10V
Vgs(th) (V) @ Id	3 @ 1mA	5 @ 250µA	1 @ 250µA	2 @ 250µA
Qg (nC) @ Vgs	30 @ 10V	63 @ 10V	14 @ 4.5V	14 @ 4.5V
Ciss (pF) @ Vds	1240 @ 15V	2659 @ 20V	1010 @ 15V	345 @ 25V
Power Dissipation (W)	2.5	2.5	2.5	2.5
Operating Temperature (°C)	-55 to 150	-55 to 175	-55 to 155	-55 to 150
Package	8-SOIC	8-SOIC	8-SO	8-SOP
Product Status	Obsolete	Active	Active	Active

Engineering Selection Recommendations

FDS4470 (Fairchild Semiconductor): The FDS4470 is an active product offering higher voltage rating (40V vs. 30V) with improved current capability (12.5A vs. 11.5A) and lower on-resistance (9 mOhm vs. 10 mOhm). This part provides enhanced performance margins and extended operating temperature range (-55°C to 175°C). The FDS4470 is suitable for applications requiring voltage headroom beyond 30V specifications. Both parts carry ROHS3 compliance and EAR99 classification.

IRF7821TRPBF (Infineon Technologies): The IRF7821TRPBF maintains the 30V voltage rating with superior current handling (13.6A vs. 11.5A) and lower on-resistance (9.1 mOhm vs. 10 mOhm). This part features reduced gate charge (14 nC vs. 30 nC) and lower input capacitance (1010 pF vs. 1240 pF), enabling faster switching characteristics. The IRF7821TRPBF is an active product with ROHS3 compliance and operates across -55°C to 155°C. The 8-SO package maintains footprint compatibility with standard 8-SOIC layouts.

TSM180N03CS RLG (Taiwan Semiconductor Corporation): The TSM180N03CS RLG maintains 30V voltage rating but delivers lower continuous current (9A vs. 11.5A) with higher on-resistance (18 mOhm vs. 10 mOhm). This part is suitable only for applications with reduced current requirements below 9A. The TSM180N03CS RLG features significantly lower input capacitance (345 pF vs. 1240 pF) and reduced gate charge (14 nC vs. 30 nC), beneficial for high-frequency switching applications. This part carries MSL 3 moisture sensitivity rating and is an active product with ROHS3 compliance.

Frequently Asked Questions (FAQ)

Q: Can the FDS4470 directly replace the FDS6680AS in all applications?

A: The FDS4470 is electrically compatible for applications operating at or below 30V. The higher 40V rating provides additional voltage margin. Current and on-resistance specifications are superior, making the FDS4470 suitable for direct substitution in designs where the original 30V specification is maintained. Verify that the application does not depend on the specific gate threshold voltage (3V for FDS6680AS vs. 5V for FDS4470).

Q: What are the switching performance differences between these substitutes?

A: Gate charge and input capacitance directly affect switching speed. The IRF7821TRPBF exhibits the lowest gate charge (14 nC) and input capacitance (1010 pF), enabling faster switching transitions compared to the FDS6680AS (30 nC, 1240 pF). The FDS4470 shows higher gate charge (63 nC) and capacitance (2659 pF), resulting in slower switching. The TSM180N03CS RLG provides the lowest capacitance (345 pF) but is limited by lower current rating.

Q: Are all substitute parts available in the same package?

A: The FDS6680AS, FDS4470, and IRF7821TRPBF are all surface mount devices in 8-pin configurations (8-SOIC or 8-SO). The TSM180N03CS RLG uses 8-SOP packaging. All four packages maintain compatible 0.154" (3.90mm) width dimensions and are suitable for standard PCB layouts. Verify specific pin assignments with manufacturer datasheets before PCB redesign.

Q: Which substitute offers the best thermal performance?

A: All four parts share identical 2.5W maximum power dissipation ratings. Thermal performance depends on application circuit design, PCB thermal management, and ambient conditions rather than device specifications. The FDS4470 and IRF7821TRPBF support higher maximum junction temperatures (175°C and 155°C respectively) compared to the FDS6680AS (150°C), providing additional thermal margin in high-temperature environments.

Q: What is the impact of different on-resistance values?

A: On-resistance directly determines conduction losses. The FDS4470 and IRF7821TRPBF both offer 9-9.1 mOhm (vs. 10 mOhm original), reducing power dissipation by approximately 10%. The TSM180N03CS RLG exhibits 18 mOhm, doubling conduction losses. For applications sensitive to power efficiency, the FDS4470 or IRF7821TRPBF are preferred. For current-limited applications below 9A, the TSM180N03CS RLG remains viable.

Q: Are there compliance or certification differences?

A: All substitute parts carry ROHS3 compliance and EAR99 export classification. The FDS6680AS, IRF7821TRPBF, and TSM180N03CS RLG specify MSL 1 or MSL 3 moisture sensitivity levels. The FDS4470 does not specify MSL rating in provided data. All parts are REACH unaffected. Verify specific compliance requirements for your application before final selection.

Q: Can the TSM180N03CS RLG be used in high-current applications?

A: No. The TSM180N03CS RLG is rated for 9A continuous current, below the FDS6680AS specification of 11.5A. This part is suitable only for applications requiring 9A or less. Using the TSM180N03CS RLG in applications exceeding 9A will result in thermal stress and potential device failure.

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