FDS8978 Equivalent & Substitute Parts

Part Overview

The FDS8978 is a dual N-channel MOSFET array manufactured by onsemi, rated for 30V drain-to-source voltage with 7.5A continuous drain current. This device features logic level gate operation and is housed in an 8-SOIC surface mount package. The FDS8978 is classified as obsolete, necessitating identification of active equivalent parts for new designs and ongoing production support. Substitute components must maintain electrical compatibility across voltage, current, and thermal specifications while accommodating the 8-SOIC package footprint.

Substiute Parts

FDS8978

onsemiIn Stock: 18384FDS8978 Datasheet

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AO4818B

Alpha & Omega Semiconductor Inc.In Stock: 6180AO4818B Datasheet

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AO4822

Alpha & Omega Semiconductor Inc.In Stock: 18720AO4822 Datasheet

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DMG4800LSD-13

Diodes IncorporatedIn Stock: 45460DMG4800LSD-13 Datasheet

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DMN3033LSD-13

Diodes IncorporatedIn Stock: 26422DMN3033LSD-13 Datasheet

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SH8KA4TB

Rohm SemiconductorIn Stock: 1432SH8KA4TB Datasheet

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STS8DN3LLH5

STMicroelectronicsIn Stock: 15280STS8DN3LLH5 Datasheet

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TSM4936DCS RLG

Taiwan Semiconductor CorporationIn Stock: 27750TSM4936DCS RLG Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the FDS8978 is determined by the following critical parameters:

Electrical Compatibility Requirements:

• Drain-to-Source Voltage (Vdss): Must equal or exceed 30V
• Continuous Drain Current (Id): Must equal or exceed 7.5A at 25°C
• On-State Resistance (Rds On): Must not significantly exceed 18mOhm to maintain thermal performance
• Gate Threshold Voltage (Vgs(th)): Must be compatible with logic level gate operation (typically ≤2.5V)
• Operating Temperature Range: Must span -55°C to 150°C

Mechanical Compatibility Requirements:

• Package Type: 8-SOIC surface mount package with 0.154" (3.90mm) width
• Configuration: Dual N-channel (2 N-Channel)
• Mounting: Surface mount technology

Regulatory & Compliance Requirements:

• RoHS3 Compliance
• Moisture Sensitivity Level (MSL): 1 (Unlimited)
• REACH Status: REACH Unaffected

Substitute parts are grouped into two categories: Direct Equivalents (matching all critical parameters within acceptable tolerances) and Enhanced Alternatives (exceeding specifications with higher current ratings or improved thermal characteristics).

Parameter Comparison

Engineering Selection Recommendations

Recommended Primary Substitutes (Active Status):

AO4818B and AO4822 (Alpha & Omega Semiconductor) are the preferred direct substitutes for the FDS8978. Both devices are active products with identical 30V/8A ratings, matching package geometry (8-SOIC), and equivalent on-state resistance (19mOhm). These parts maintain full RoHS3 compliance and MSL-1 moisture sensitivity rating. The marginal increase in drain current (8A vs. 7.5A) and gate charge reduction (18nC vs. 26nC) provide improved performance margins without design modification.

STS8DN3LLH5 (STMicroelectronics) offers enhanced specifications with 10A continuous drain current, reduced gate charge (5.4nC), and lower gate threshold voltage (1V), all within the 8-SOIC package. This part is actively produced and suitable for applications requiring improved switching performance and thermal headroom.

DMG4800LSD-13 (Diodes Incorporated) provides equivalent 7.5A current rating with superior on-state resistance (16mOhm @ 9A, 10V) and significantly reduced gate charge (8.56nC @ 5V). This active product is compatible with the FDS8978 footprint and electrical requirements.

Secondary Alternatives (Limited Availability):

DMN3033LSD-13 (Diodes Incorporated) is an active product with 6.9A rating, slightly below the FDS8978 specification. This part is suitable only for applications where the 7.5A requirement can be relaxed.

Parts Not Recommended for New Designs:

SH8KA4TB (Rohm Semiconductor) and TSM4936DCS RLG (Taiwan Semiconductor) carry "Not For New Designs" status. While electrically compatible, these parts should not be selected for new product development. TSM4936DCS RLG additionally carries MSL-3 moisture sensitivity, requiring controlled storage conditions.

Compliance & Regulatory Alignment:

All recommended substitutes maintain RoHS3 compliance and REACH unaffected status, matching the FDS8978 regulatory profile. MSL-1 rating is preserved across primary recommendations, ensuring compatibility with standard PCB assembly processes.

Frequently Asked Questions (FAQ)

Q: Can I directly replace FDS8978 with AO4818B or AO4822 without PCB modifications?

A: Yes. Both AO4818B and AO4822 are pin-compatible with the FDS8978 in the 8-SOIC package. Electrical specifications are equivalent or superior, requiring no circuit design changes. Both parts are active products with full RoHS3 compliance.

Q: What is the primary reason the FDS8978 is obsolete?

A: The FDS8978 is classified as obsolete by onsemi. Active equivalent products from other manufacturers (Alpha & Omega, STMicroelectronics, Diodes Incorporated) provide equivalent or superior performance and are recommended for all new designs and production continuity.

Q: How do I select between AO4818B, DMG4800LSD-13, and STS8DN3LLH5?

A: Selection depends on application requirements. AO4818B and AO4822 provide direct electrical equivalence with 8A rating. DMG4800LSD-13 offers superior on-state resistance (16mOhm) at equivalent 7.5A current. STS8DN3LLH5 provides the highest current rating (10A) with lowest gate charge (5.4nC), suitable for high-frequency switching applications. All three are active products in 8-SOIC packages.

Q: Are there package compatibility concerns between 8-SOIC, 8-SO, and 8-SOP variants?

A: While all variants share the 0.154" (3.90mm) width specification, 8-SO and 8-SOP packages may have minor pitch or lead configuration differences. Verify PCB footprint compatibility before substitution. 8-SOIC packages (AO4818B, AO4822, STS8DN3LLH5) are direct mechanical equivalents to the FDS8978.

Q: Why does TSM4936DCS RLG have higher on-state resistance (36mOhm) than the FDS8978?

A: TSM4936DCS RLG is rated for lower continuous drain current (5.9A vs. 7.5A), resulting in higher on-state resistance specification. This part is not recommended for applications requiring the full 7.5A specification. Additionally, this part carries "Not For New Designs" status and MSL-3 moisture sensitivity.

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

A: Gate charge affects switching speed and driver power requirements. Lower gate charge (STS8DN3LLH5 at 5.4nC) enables faster switching and reduced driver losses. Higher gate charge (FDS8978 at 26nC) requires longer switching times. Selection depends on circuit switching frequency and driver capability.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All recommended substitute parts (AO4818B, AO4822, DMG4800LSD-13, DMN3033LSD-13, STS8DN3LLH5) are RoHS3 compliant and REACH unaffected, matching the FDS8978 regulatory profile.

Q: What does MSL-1 vs. MSL-3 mean for component handling?

A: MSL-1 (Unlimited) indicates the component has unlimited shelf life and requires no special moisture control during storage or assembly. MSL-3 (168 Hours) requires controlled humidity storage and limits the time between package opening and PCB assembly to 168 hours. FDS8978 and all primary recommended substitutes are MSL-1 rated.

Q: Can I use SH8KA4TB or TSM4936DCS RLG in production?

A: Both parts are electrically compatible but carry "Not For New Designs" status. SH8KA4TB may be used for legacy product support or repair applications. TSM4936DCS RLG additionally carries MSL-3 moisture sensitivity, adding handling complexity. For new designs, select from active products: AO4818B, AO4822, DMG4800LSD-13, or STS8DN3LLH5.