TOP246FN Equivalent & Substitute Parts Reference

Part Overview

The TOP246FN is an offline flyback converter IC from Power Integrations' TOPSwitch®-GX series, designed for isolated power supply applications. This component integrates a high-voltage switch with control circuitry in a TO-262-7C through-hole package, delivering up to 125 W output power with built-in fault protection including current limiting, over-temperature, and over-voltage monitoring.

The TOP246FN is classified as obsolete. Identifying suitable substitute components is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for legacy systems or new designs requiring equivalent functionality.

Substiute Parts

TOP246FN

Power IntegrationsIn Stock: 1560TOP246FN Datasheet

Current PartRFQ

TOP268KG-TL

Power IntegrationsIn Stock: 38311TOP268KG-TL Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the TOP246FN is evaluated based on the following critical parameters that define functional equivalence within Power Integrations' offline flyback converter product line:

Topology & Isolation: Both the main part and substitute must operate as isolated flyback converters with internal switching capability.

Voltage Rating: Breakdown voltage must meet or exceed the 700V specification to ensure safe operation across input voltage ranges.

Switching Frequency: Operating frequency range must overlap or be compatible with 66kHz to 132kHz to maintain EMI characteristics and transformer design compatibility.

Power Capacity: Output power rating must support the application requirements; lower-rated substitutes may be acceptable for reduced-power variants.

Fault Protection: Presence of current limiting, over-temperature, and over-voltage protection ensures equivalent safety functionality.

Control Features: Frequency control capability must be maintained for equivalent regulation performance.

Operating Temperature Range: The -40°C to 150°C junction temperature range must be supported.

Compliance & Certifications: RoHS compliance and REACH status must be maintained for regulatory equivalence.

The TOP268KG-TL qualifies as a substitute based on these criteria, though with specific parameter differences noted in the comparison table below.

Parameter Comparison

Engineering Selection Recommendations

For Active Production & New Designs:

The TOP268KG-TL is the recommended substitute for the obsolete TOP246FN. This component is in active production status, ensuring long-term supply chain availability. Both parts are RoHS compliant and REACH unaffected, meeting current regulatory requirements.

Design Considerations:

The TOP268KG-TL operates at a lower power rating (73 W versus 125 W). This substitute is suitable for applications requiring up to 73 W output power. For designs requiring the full 125 W capacity of the original TOP246FN, alternative higher-power rated converters from the TOPSwitch®-JX series should be evaluated.

Package & Assembly Impact:

The TOP268KG-TL uses a 12-BESOP surface-mount package, whereas the TOP246FN uses a through-hole TO-262-7 package. PCB layout redesign is required for substitution. The TOP268KG-TL includes an exposed pad for improved thermal management in surface-mount applications.

Moisture Sensitivity:

The TOP268KG-TL has MSL rating 3 (168 hours), compared to MSL 1 (unlimited) for the TOP246FN. Storage and handling procedures must comply with moisture sensitivity requirements.

Protection Features:

The TOP268KG-TL provides enhanced fault protection including over-load and short-circuit detection, offering improved safety margins compared to the original part.

Frequently Asked Questions (FAQ)

Q: Can the TOP268KG-TL directly replace the TOP246FN without circuit modifications?

A: No. While both are isolated flyback converters with compatible topologies and control features, the TOP268KG-TL has a lower power rating (73 W versus 125 W) and different package type (surface-mount 12-BESOP versus through-hole TO-262-7). Circuit redesign and PCB layout changes are required.

Q: What is the power rating difference, and does it affect substitution?

A: The TOP246FN is rated for 125 W output power, while the TOP268KG-TL is rated for 73 W. The substitute is suitable only for applications requiring up to 73 W. For higher-power applications, alternative components must be selected.

Q: Are there voltage compatibility concerns between the 700V and 725V breakdown ratings?

A: No. The TOP268KG-TL's 725V breakdown voltage exceeds the TOP246FN's 700V rating, providing equivalent or improved voltage margin. Both are compatible with standard offline AC input voltage ranges.

Q: How do the switching frequency specifications compare?

A: Both parts support 66kHz and 132kHz switching frequencies. The TOP246FN specifies a continuous range (66kHz ~ 132kHz), while the TOP268KG-TL specifies discrete frequencies (66kHz, 132kHz). Frequency control capability is maintained in both.

Q: What is the impact of the different duty cycle specifications?

A: The TOP246FN operates at 66.5% duty cycle, while the TOP268KG-TL operates at 78%. Duty cycle is design-dependent and determined by transformer turns ratio and load conditions. This parameter difference does not prevent substitution but requires transformer design verification.

Q: Does the enhanced fault protection in the TOP268KG-TL affect compatibility?

A: No. The TOP268KG-TL includes additional over-load and short-circuit protection beyond the TOP246FN's current limiting, over-temperature, and over-voltage protection. Enhanced protection is a beneficial feature that improves system reliability.

Q: What are the implications of the MSL rating difference?

A: The TOP246FN has MSL 1 (unlimited moisture sensitivity), while the TOP268KG-TL has MSL 3 (168-hour limit). The substitute requires controlled storage conditions and must be used within 168 hours of package opening. Standard moisture-barrier packaging and desiccant storage are required.

Q: Is PCB layout redesign mandatory for substitution?

A: Yes. The different package types (through-hole TO-262-7 versus surface-mount 12-BESOP) require complete PCB layout redesign. Pin assignments and thermal management approaches differ between the packages.

Q: Are there any compliance or certification concerns with substitution?

A: No. Both parts are RoHS compliant and REACH unaffected. Regulatory compliance is maintained. However, end-product certification may require re-validation depending on safety and EMC standards applicable to the application.