STS9D8NH3LL Equivalent & Substitute Parts

Part Overview

The STS9D8NH3LL is a dual N-channel MOSFET array manufactured by STMicroelectronics, part of the STripFET™ series. This device integrates two N-channel MOSFETs in a single 8-SOIC surface mount package, designed for logic-level gate drive applications with a maximum drain-source voltage of 30V and continuous drain current ratings of 8A to 9A per channel.

The STS9D8NH3LL is classified as obsolete. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this component.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	30	V
Continuous Drain Current (Id) @ 25°C	8, 9	A
On-State Resistance (Rds On) @ Id, Vgs	22 mOhm @ 4A, 10V	mOhm
Gate Threshold Voltage (Vgs(th)) @ Id	1	V @ 250µA
Gate Charge (Qg) @ Vgs	10	nC @ 4.5V
Input Capacitance (Ciss) @ Vds	857	pF @ 25V
Maximum Power Dissipation	2	W
Operating Temperature (TJ)	150	°C
Configuration	2 N-Channel (Dual)	—
Package / Case	8-SOIC (0.154", 3.90mm Width)	—
FET Feature	Logic Level Gate	—
Technology	MOSFET (Metal Oxide)	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the STS9D8NH3LL is determined by the following critical parameters:

Mandatory Matching Parameters:

Drain to Source Voltage (Vdss): 30V
Configuration: 2 N-Channel (Dual)
Package / Case: 8-SOIC (0.154", 3.90mm Width)
FET Feature: Logic Level Gate
Technology: MOSFET (Metal Oxide)

Performance Parameters (Allowable Variation):

Continuous Drain Current (Id) @ 25°C: 6.7A to 10A (encompasses the 8A–9A range of the main part)
On-State Resistance (Rds On): 18 mOhm to 23 mOhm (within acceptable switching and thermal performance range)
Gate Threshold Voltage (Vgs(th)): 1V to 3V (logic-level gate drive compatibility)
Gate Charge (Qg): 10 nC to 26 nC (acceptable for gate drive circuit design)
Input Capacitance (Ciss): 448 pF to 1270 pF (within typical gate drive specifications)
Maximum Power Dissipation: 1.42W to 2W (thermal management compatibility)
Operating Temperature (TJ): Minimum –55°C to maximum 150°C (includes or exceeds the main part's 150°C maximum)

Compliance Parameters:

RoHS Status: ROHS3 Compliant
Moisture Sensitivity Level (MSL): 1 (Unlimited)
REACH Status: REACH Unaffected
ECCN: EAR99
HTSUS: 8541.29.0095

Substitute parts must meet all mandatory matching parameters and comply with all regulatory and environmental standards. Performance parameters must fall within the specified ranges to ensure functional equivalence in the target application.

Parameter Comparison

Part Number	Manufacturer	Vdss (V)	Id @ 25°C (A)	Rds On (mOhm)	Vgs(th) (V)	Qg (nC)	Ciss (pF)	Power Max (W)	Tj Max (°C)	Package	Status
STS9D8NH3LL	STMicroelectronics	30	8, 9	22 @ 4A, 10V	1 @ 250µA	10 @ 4.5V	857 @ 25V	2	150	8-SOIC	Obsolete
AO4818B	Alpha & Omega Semiconductor Inc.	30	8	19 @ 8A, 10V	2.4 @ 250µA	18 @ 10V	888 @ 15V	2	150	8-SOIC	Active
AO4822A	Alpha & Omega Semiconductor Inc.	30	8	19 @ 8A, 10V	2.4 @ 250µA	18 @ 10V	888 @ 15V	2	150	8-SOIC	Active
AO4842	Alpha & Omega Semiconductor Inc.	30	—	22 @ 7.5A, 10V	2.6 @ 250µA	11 @ 10V	448 @ 15V	2	150	8-SOIC	Not For New Designs
AO4854	Alpha & Omega Semiconductor Inc.	30	8	19 @ 8A, 10V	2.4 @ 250µA	18 @ 10V	888 @ 15V	2	150	8-SOIC	Active
DMG4822SSD-13	Diodes Incorporated	30	10	20 @ 8.5A, 10V	3 @ 250µA	10.5 @ 10V	478.9 @ 16V	1.42	150	8-SOIC	Active
DMN3018SSD-13	Diodes Incorporated	30	6.7	22 @ 10A, 10V	2.1 @ 250µA	13.2 @ 10V	697 @ 15V	1.5	150	8-SOIC	Active
DMN3033LSD-13	Diodes Incorporated	30	6.9	20 @ 6.9A, 10V	2.1 @ 250µA	13 @ 10V	725 @ 15V	2	150	8-SOIC	Active
DMN3033LSDQ-13	Diodes Incorporated	30	6.9	20 @ 6.9A, 10V	2.1 @ 250µA	13 @ 10V	725 @ 15V	2	150	8-SOIC	Active
FDS8978	onsemi	30	7.5	18 @ 7.5A, 10V	2.5 @ 250µA	26 @ 10V	1270 @ 15V	1.6	150	8-SOIC	Obsolete
FDS8984	onsemi	30	7	23 @ 7A, 10V	2.5 @ 250µA	13 @ 10V	635 @ 15V	1.6	150	8-SOIC	Active

Engineering Selection Recommendations

Primary Substitutes (Active Product Status):

The following parts are recommended as primary substitutes due to active product status, full compliance with regulatory standards, and parameter alignment within acceptable ranges:

AO4818B, AO4822A, AO4854 (Alpha & Omega Semiconductor Inc.): These three parts are electrically equivalent with identical 30V Vdss, 8A continuous drain current, 19 mOhm Rds On, and 2W maximum power dissipation. All three are ROHS3 compliant and carry active product status. AO4822A offers the highest inventory availability (210,100 pcs).
DMG4822SSD-13 (Diodes Incorporated): Offers 10A continuous drain current, exceeding the main part's 8A–9A range, with 20 mOhm Rds On and 1.42W power dissipation. Active status and full compliance.
DMN3033LSD-13, DMN3033LSDQ-13 (Diodes Incorporated): Both provide 6.9A continuous drain current with 20 mOhm Rds On and 2W power dissipation. Active status and full compliance. DMN3033LSDQ-13 includes additional qualification.
FDS8984 (onsemi): Provides 7A continuous drain current with 23 mOhm Rds On and 1.6W power dissipation. Active product status and full compliance.

Secondary Substitutes (Obsolete or Not For New Designs):

AO4842 (Alpha & Omega Semiconductor Inc.): Classified as "Not For New Designs." Use only for legacy system maintenance or repair applications where no active alternative is available.
FDS8978 (onsemi): Classified as obsolete. Use only for legacy system maintenance or repair applications where no active alternative is available.

Selection Criteria:

For new designs, select from the primary substitute group. For legacy system support, secondary substitutes are acceptable only when primary alternatives are unavailable. All recommended substitutes maintain the 8-SOIC package form factor, 30V Vdss rating, dual N-channel configuration, logic-level gate drive capability, and 150°C maximum junction temperature of the original part. All substitutes are ROHS3 compliant, MSL 1 (Unlimited), REACH unaffected, and carry EAR99 ECCN classification.

Frequently Asked Questions (FAQ)

Q: Can I use AO4854 as a direct replacement for STS9D8NH3LL?

A: Yes. AO4854 meets all mandatory matching parameters: 30V Vdss, dual N-channel configuration, 8-SOIC package, logic-level gate drive, and 2W power dissipation. It is ROHS3 compliant with active product status. The 19 mOhm Rds On is lower than the main part's 22 mOhm, resulting in improved efficiency.

Q: What is the difference between AO4818B, AO4822A, and AO4854?

A: All three parts are electrically identical with respect to the parameters provided: 30V Vdss, 8A continuous drain current, 19 mOhm Rds On, 2W power dissipation, and 8-SOIC package. The differences lie in packaging format (Tape & Reel for AO4818B, unspecified for AO4822A, and Bulk for AO4854) and inventory availability. Selection should be based on procurement requirements and supply chain availability.

Q: Why do some substitute parts have lower continuous drain current ratings than the main part?

A: The STS9D8NH3LL is rated for 8A to 9A continuous drain current. Substitute parts with lower ratings (such as DMN3018SSD-13 at 6.7A or DMN3033LSD-13 at 6.9A) remain functionally equivalent if the application does not require the full 8A–9A current range. These parts maintain the same 30V Vdss, package form factor, and logic-level gate drive capability. Application-specific current requirements must be verified before selection.

Q: Can I use DMG4822SSD-13, which has 10A continuous drain current, instead of STS9D8NH3LL?

A: Yes. DMG4822SSD-13 exceeds the main part's current rating (10A versus 8A–9A) and maintains all other mandatory parameters: 30V Vdss, dual N-channel configuration, 8-SOIC package, and logic-level gate drive. The 20 mOhm Rds On is within acceptable range. This part is suitable for applications requiring higher current capacity or margin.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed in this document are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity level, REACH unaffected status, and EAR99 ECCN classification, matching the regulatory profile of the main part.

Q: Should I use FDS8978 or AO4842 for new designs?

A: No. FDS8978 is classified as obsolete, and AO4842 is classified as "Not For New Designs." For new designs, select from the active product group: AO4818B, AO4822A, AO4854, DMG4822SSD-13, DMN3033LSD-13, DMN3033LSDQ-13, or FDS8984. These parts carry active product status and are supported for ongoing production.

Q: What is the significance of the 8-SOIC package specification?

A: The 8-SOIC (Small Outline Integrated Circuit) package with 0.154" (3.90mm) width is a standard surface mount form factor. All substitute parts maintain this identical package specification, ensuring mechanical and electrical compatibility with existing PCB layouts and assembly processes. No board redesign is required when substituting between parts with matching 8-SOIC packages.

Q: How do I determine which substitute part is best for my application?

A: Evaluate the following in order of priority: (1) Product status—select active parts for new designs; (2) Continuous drain current requirement—ensure the substitute meets or exceeds your application's maximum current; (3) On-state resistance (Rds On)—lower values reduce power dissipation and heat generation; (4) Inventory availability—confirm supply chain access; (5) Packaging format—select based on procurement and assembly requirements (Tape & Reel, Bulk, or Cut Tape).

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