TOP243FN Equivalent & Substitute Parts

Part Overview

The TOP243FN is an offline switch flyback converter IC manufactured by Power Integrations, designed for isolated power supply applications. This device operates in the TOPSwitch®-GX series and delivers 45W of power using flyback topology with integrated frequency control and comprehensive fault protection. The TOP243FN is classified as obsolete, making identification of functionally equivalent active alternatives essential for new designs and production continuity.

Substiute Parts

TOP243FN

Power IntegrationsIn Stock: 1509TOP243FN Datasheet

Current PartRFQ

TOP265KG-TL

Power IntegrationsIn Stock: 4170TOP265KG-TL Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the TOP243FN is determined by the following critical parameters:

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

Voltage Rating: The substitute breakdown voltage (725V for TOP265KG-TL) must equal or exceed the original specification (700V).

Switching Frequency: The substitute must support the same switching frequency range or compatible frequencies (66kHz, 132kHz).

Power Capacity: The substitute power rating (53W for TOP265KG-TL) must meet or exceed the original 45W requirement.

Fault Protection: The substitute must include equivalent or enhanced protection features (current limiting, over temperature, over voltage).

Control Features: Frequency control capability must be maintained.

Temperature Range: Operating temperature specifications must be identical or broader.

Manufacturer Consistency: Both parts are manufactured by Power Integrations, ensuring design compatibility within the TOPSwitch® family.

The TOP265KG-TL qualifies as a substitute because it meets all these criteria while offering enhanced specifications and active product status.

Parameter Comparison

Engineering Selection Recommendations

For Obsolete Part Replacement: The TOP243FN is classified as obsolete. The TOP265KG-TL is an active product within the Power Integrations TOPSwitch® family and provides functional equivalence with enhanced specifications.

Compliance & Certifications: Both parts maintain RoHS compliance and REACH unaffected status, ensuring regulatory continuity. Both carry EAR99 ECCN classification.

Performance Headroom: The TOP265KG-TL offers 8W additional power capacity (53W vs. 45W) and higher breakdown voltage (725V vs. 700V), providing design margin for existing 45W applications.

Enhanced Protection: The TOP265KG-TL includes additional fault protection features (over load, short circuit) compared to the TOP243FN, improving system reliability.

Package Transition: The substitution requires a package change from through-hole TO-262-7 to surface-mount 12-ESOP. PCB layout redesign is necessary.

Series Evolution: The transition from TOPSwitch®-GX to TOPSwitch®-JX represents a product line advancement within the same manufacturer ecosystem.

Frequently Asked Questions (FAQ)

Q: Can TOP265KG-TL directly replace TOP243FN without circuit modifications?

A: Functional substitution is possible, but circuit redesign is required due to package change (through-hole to surface-mount) and different pin configurations (6 leads vs. 11 leads). The electrical characteristics are compatible for 45W applications.

Q: What are the key differences between TOP243FN and TOP265KG-TL?

A: Primary differences include: product status (obsolete vs. active), series generation (GX vs. JX), package type (TO-262-7 through-hole vs. 12-ESOP surface-mount), power rating (45W vs. 53W), breakdown voltage (700V vs. 725V), duty cycle (66.5% vs. 78%), and fault protection features (enhanced in TOP265KG-TL).

Q: Is the TOP265KG-TL suitable for 45W applications originally designed for TOP243FN?

A: Yes. The TOP265KG-TL exceeds the original 45W specification with 53W capacity and maintains compatible operating temperature range (-40°C ~ 150°C). The higher breakdown voltage and additional protection features provide enhanced performance margins.

Q: What packaging considerations apply to this substitution?

A: The TOP243FN uses through-hole TO-262-7 packaging with 6 leads. The TOP265KG-TL uses surface-mount 12-ESOP packaging with 11 leads and an exposed pad. PCB redesign, including trace routing and thermal management modifications, is required.

Q: Are both parts RoHS compliant?

A: Yes. Both TOP243FN and TOP265KG-TL are RoHS compliant and REACH unaffected, maintaining regulatory compliance for new designs.

Q: What is the switching frequency compatibility?

A: Both parts support 66kHz and 132kHz switching frequencies. The TOP243FN specifies a range (66kHz ~ 132kHz), while TOP265KG-TL specifies discrete frequencies (66kHz, 132kHz). Both are compatible for applications using these frequencies.

Q: Does the TOP265KG-TL provide better fault protection?

A: Yes. The TOP265KG-TL includes over load and short circuit protection in addition to current limiting, over temperature, and over voltage protection found in TOP243FN. This represents enhanced system protection.