FDS6990AS Equivalent & Substitute Parts

Part Overview

The FDS6990AS is a dual N-channel MOSFET array manufactured by onsemi, rated for 30V drain-to-source voltage and 7.5A continuous drain current in an 8-SOIC surface mount package. This device features Logic Level Gate operation and is part of the PowerTrench® and SyncFET™ series. The FDS6990AS is classified as Obsolete, making identification of functionally equivalent substitute components necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	30	V
Current - Continuous Drain (Id) @ 25°C	7.5	A
Rds On (Max) @ Id, Vgs	22 @ 7.5A, 10V	mOhm
Vgs(th) (Max) @ Id	3 @ 1mA	V
Gate Charge (Qg) (Max) @ Vgs	14 @ 5V	nC
Input Capacitance (Ciss) (Max) @ Vds	550 @ 15V	pF
Power - Max	900	mW
Operating Temperature Range	-55 to 150	°C (TJ)
Configuration	2 N-Channel (Dual)
Package / Case	8-SOIC (0.154", 3.90mm Width)
FET Feature	Logic Level Gate

Substitute Part Grouping Explanation

Substitution of the FDS6990AS is determined by the following critical parameters:

Voltage Rating: All substitute parts must maintain a minimum Vdss of 30V to ensure compatibility with the original circuit voltage specifications.

Current Rating: Substitute parts must support a continuous drain current (Id) of at least 7.5A at 25°C to handle the same load conditions.

On-Resistance (Rds On): The maximum on-resistance specification of 22 mOhm at 7.5A, 10V establishes the switching loss and thermal performance baseline. Substitute parts with equal or lower Rds On values maintain equivalent or improved performance.

Package Compatibility: All substitute parts are specified in 8-SOIC surface mount packages with identical 0.154" (3.90mm) width, ensuring direct PCB layout compatibility.

Configuration: All substitute parts maintain the dual N-channel (2 N-Channel) configuration required for the original circuit topology.

Logic Level Gate Operation: Substitute parts feature Logic Level Gate capability, enabling direct gate drive compatibility with standard logic-level control signals.

Operating Temperature Range: All substitute parts support the -55°C to 150°C operating temperature range, maintaining thermal performance across the full application envelope.

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On (mOhm)	Power Max (mW)	Vgs(th) (V)	Qg (nC)	Ciss (pF)	Product Status	Package
FDS6990AS	onsemi	30	7.5	22 @ 7.5A, 10V	900	3 @ 1mA	14 @ 5V	550 @ 15V	Obsolete	8-SOIC
AO4842	Alpha & Omega Semiconductor Inc.	30	—	22 @ 7.5A, 10V	2000	2.6 @ 250µA	11 @ 10V	448 @ 15V	Not For New Designs	8-SOIC
AO4882	Alpha & Omega Semiconductor Inc.	40	8	19 @ 8A, 10V	2000	2.4 @ 250µA	12 @ 10V	415 @ 20V	Active	8-SOIC
DMN3033LSD-13	Diodes Incorporated	30	6.9	20 @ 6.9A, 10V	2000	2.1 @ 250µA	13 @ 10V	725 @ 15V	Active	8-SOIC
SH8KA4TB	Rohm Semiconductor	30	9	21.4 @ 9A, 10V	3000	2.5 @ 1mA	15.5 @ 10V	640 @ 15V	Not For New Designs	8-SOIC
STS10DN3LH5	STMicroelectronics	30	10	21 @ 5A, 10V	2500	1 @ 250µA	4.6 @ 5V	475 @ 25V	Not For New Designs	8-SOIC
STS8DN3LLH5	STMicroelectronics	30	10	19 @ 5A, 10V	2700	1 @ 250µA	5.4 @ 4.5V	724 @ 25V	Active	8-SOIC
TSM4936DCS RLG	Taiwan Semiconductor Corporation	30	5.9 (Ta)	36 @ 5.9A, 10V	3000	3 @ 250µA	13 @ 10V	610 @ 15V	Not For New Designs	8-SOIC

Engineering Selection Recommendations

Primary Substitute: STS8DN3LLH5

The STS8DN3LLH5 from STMicroelectronics is the recommended primary substitute. This device maintains 30V Vdss rating, supports 10A continuous drain current (exceeding the 7.5A requirement), and delivers 19 mOhm on-resistance at 5A, 10V—superior to the FDS6990AS specification. The part is classified as Active, ensuring long-term availability and supply chain stability. RoHS3 compliance and unlimited moisture sensitivity level (MSL 1) match the original device specifications. The 8-SOIC package provides direct mechanical and electrical compatibility.

Secondary Substitute: AO4882

The AO4882 from Alpha & Omega Semiconductor Inc. provides an alternative with enhanced voltage headroom. This device is rated for 40V Vdss and 8A continuous drain current, supporting applications requiring higher voltage margins. The 19 mOhm on-resistance at 8A, 10V delivers improved switching performance. Active product status ensures ongoing availability. The 8-SOIC package maintains form-factor compatibility. This substitute is suitable for designs where voltage derating or future specification margin is required.

Tertiary Substitute: DMN3033LSD-13

The DMN3033LSD-13 from Diodes Incorporated maintains the 30V Vdss rating with 6.9A continuous drain current. The 20 mOhm on-resistance at 6.9A, 10V is within acceptable tolerance of the original specification. Active product status and RoHS3 compliance ensure procurement viability. The 8-SOIC package provides direct compatibility. This substitute is applicable for designs where the 6.9A current rating is sufficient.

Obsolete Alternatives: AO4842, SH8KA4TB, STS10DN3LH5, TSM4936DCS RLG

These parts are classified as Not For New Designs or carry higher MSL ratings (TSM4936DCS RLG: MSL 3). While electrically compatible, these devices are not recommended for new designs due to product lifecycle status and potential supply constraints.

Frequently Asked Questions (FAQ)

Q: Can the STS8DN3LLH5 directly replace the FDS6990AS without circuit modification?

A: Yes. The STS8DN3LLH5 maintains identical 30V Vdss rating, 8-SOIC package geometry, and Logic Level Gate operation. The 10A continuous drain current exceeds the 7.5A requirement, and the 19 mOhm on-resistance is superior to the original 22 mOhm specification. No circuit modifications are required.

Q: What is the significance of the on-resistance (Rds On) parameter in substitution?

A: On-resistance directly determines switching losses and thermal performance. Lower Rds On values reduce power dissipation and junction temperature rise. Substitute parts with equal or lower Rds On values maintain or improve thermal performance. The FDS6990AS specifies 22 mOhm maximum; substitutes with 19-21 mOhm values provide equivalent or superior performance.

Q: Why is the AO4882 rated for 40V when the original circuit operates at 30V?

A: The 40V rating provides voltage derating margin for transient overshoot protection and design safety. In 30V applications, the AO4882 operates well within its voltage specification, offering enhanced reliability. The higher voltage rating does not affect circuit operation at 30V.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed carry RoHS3 compliance certification, matching the original FDS6990AS specification. This ensures environmental and regulatory compatibility across all alternatives.

Q: What does "Not For New Designs" product status mean for substitution?

A: Parts classified as Not For New Designs are in end-of-life phase and may have limited availability or extended lead times. While electrically functional, these parts are not recommended for new circuit designs. Active-status alternatives (STS8DN3LLH5, AO4882, DMN3033LSD-13) are preferred for new applications.

Q: Can the TSM4936DCS RLG be used as a substitute despite its higher MSL rating?

A: The TSM4936DCS RLG carries MSL 3 (168 Hours) versus the original MSL 1 (Unlimited). This indicates higher moisture sensitivity and requires stricter handling, storage, and reflow procedures. While electrically compatible, the additional process controls and supply chain constraints make this substitute less practical than Active alternatives with MSL 1 ratings.

Q: How does gate charge (Qg) affect substitution compatibility?

A: Gate charge determines the energy required to switch the MOSFET on and off. Lower Qg values reduce gate drive power requirements and enable faster switching. The FDS6990AS specifies 14 nC at 5V. Substitute parts with 4.6-15.5 nC gate charge are compatible; lower values (STS10DN3LH5: 4.6 nC) provide faster switching response.

Q: Is the 8-SOIC package identical across all substitute parts?

A: Yes. All substitute parts are specified in 8-SOIC packages with 0.154" (3.90mm) width, ensuring identical PCB footprint and pin compatibility. Direct board-level substitution is possible without layout modifications.

Q: What is the practical current rating difference between the FDS6990AS (7.5A) and STS8DN3LLH5 (10A)?

A: The STS8DN3LLH5 supports 33% higher continuous drain current. In applications operating at or below 7.5A, this provides thermal margin and extended device lifetime. The higher current rating does not affect circuit operation; it only improves reliability and thermal performance.

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