FSDH321 Equivalent & Substitute Parts

Part Overview

The FSDH321 is an offline switch flyback converter IC manufactured by onsemi, designed for isolated power management applications. This 8-DIP through-hole component operates at 100kHz switching frequency with 17W power capability and integrated fault protection including current limiting, overload, overtemperature, and overvoltage detection.

The FSDH321 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support legacy system maintenance and new production requirements.

Substiute Parts

FSDH321

onsemiIn Stock: 6371FSDH321 Datasheet

Current PartRFQ

NCP1075AAP100G

onsemiIn Stock: 908NCP1075AAP100G Datasheet

MFR RecommendedRFQ

FSQ110

Fairchild SemiconductorIn Stock: 6417FSQ110 Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the FSDH321 are identified based on the following critical parameters that determine functional compatibility:

Core Substitution Criteria:

• Topology: Flyback converter architecture
• Output Isolation: Isolated configuration
• Internal Switch(es): Integrated switching element
• Switching Frequency: 100kHz operation
• Voltage - Breakdown: Minimum 650V rating
• Voltage - Supply Range: Overlap with 8V ~ 20V input specification
• Power Rating: Minimum 17W capability
• Fault Protection: Current limiting, overtemperature, and overvoltage protection
• Mounting Type: Through-hole compatible
• Package Compatibility: 8-DIP or equivalent pin-compatible packages

Two substitute parts meet these criteria with varying degrees of parametric alignment and product status considerations.

Parameter Comparison

Engineering Selection Recommendations

NCP1075AAP100G (onsemi - MFR Recommended Substitute)

This part is designated as the manufacturer-recommended substitute. It maintains onsemi sourcing continuity and carries active product status with ROHS3 compliance certification. The NCP1075AAP100G operates within the required 100kHz switching frequency and provides isolated flyback topology with integrated fault protection. The 700V breakdown voltage exceeds the FSDH321 specification, providing additional voltage margin. The supply voltage range extends to 6.5V minimum, offering broader input compatibility. Operating temperature range extends to -40°C ~ 125°C, supporting wider environmental conditions. Power rating of 14W is below the FSDH321 specification; applications requiring the full 17W capability must be evaluated against actual load requirements. The package uses 7 leads within an 8-DIP footprint; PCB layout verification is required to confirm pin compatibility.

FSQ110 (Fairchild Semiconductor - Parametric Equivalent)

This part provides parametric equivalence with matching 650V breakdown voltage, 8V ~ 20V supply range, 100kHz switching frequency, and 17W power rating. The FSQ110 maintains identical fault protection features and operating temperature range as the FSDH321. Active product status ensures ongoing availability. The 8-MDIP package maintains full pin and footprint compatibility with the original 8-DIP specification. Sourcing transitions from onsemi to Fairchild Semiconductor; supply chain and qualification considerations apply.

Frequently Asked Questions (FAQ)

Q: Can the NCP1075AAP100G directly replace the FSDH321 in existing PCB designs?

A: The NCP1075AAP100G uses 7 leads within an 8-DIP package footprint. While the physical dimensions match the 8-DIP standard, the reduced lead count requires PCB layout verification. Pin-to-pin compatibility must be confirmed against the specific application schematic before implementation.

Q: What is the significance of the power rating difference between FSDH321 (17W) and NCP1075AAP100G (14W)?

A: The NCP1075AAP100G is rated for 14W maximum output power, compared to the FSDH321 at 17W. Applications operating below 14W output power are unaffected. Designs requiring the full 17W capability must evaluate whether the NCP1075AAP100G can support the intended load, considering thermal management and duty cycle constraints.

Q: Why does the NCP1075AAP100G have a lower minimum supply voltage (6.5V vs. 8V)?

A: The NCP1075AAP100G extends the minimum supply voltage specification to 6.5V, providing broader input range compatibility. This represents an enhancement over the FSDH321 specification and does not create compatibility issues for applications designed for 8V ~ 20V operation.

Q: Is the FSQ110 a suitable alternative if onsemi parts are unavailable?

A: The FSQ110 provides parametric equivalence across all critical specifications: 650V breakdown voltage, 8V ~ 20V supply range, 100kHz switching frequency, 17W power rating, and identical fault protection features. The 8-MDIP package maintains full footprint compatibility. Sourcing from Fairchild Semiconductor introduces supply chain considerations and may require qualification review depending on application requirements.

Q: What compliance certifications apply to these substitute parts?

A: The FSDH321 and NCP1075AAP100G both carry ROHS3 compliance certification. Both parts are classified as REACH Unaffected and carry EAR99 ECCN designation. The FSQ110 compliance status is not specified in the available documentation.

Q: How do the operating temperature ranges compare?

A: The FSDH321 and FSQ110 both operate across -25°C ~ 85°C (TA). The NCP1075AAP100G extends the operating range to -40°C ~ 125°C (TJ), supporting wider environmental conditions. Applications with temperature requirements within the -25°C ~ 85°C range are compatible with all three parts.