TOP255LN Equivalent & Substitute Parts Reference

Part Overview

The TOP255LN is an offline flyback converter IC from Power Integrations' TOPSwitch®-HX series, designed for isolated power supply applications. This component operates at 66kHz or 132kHz switching frequency with 81W power capability and 700V breakdown voltage rating. The TOP255LN is classified as obsolete, necessitating identification of active equivalent alternatives for new designs and production continuity. Substitute parts must maintain electrical compatibility across critical parameters including topology, switching frequency, voltage rating, fault protection features, and thermal operating range to ensure functional equivalence in flyback converter applications.

Key Parameters

Parameter	TOP255LN	Unit
Manufacturer	Power Integrations	—
Series	TOPSwitch®-HX	—
Topology	Flyback	—
Output Isolation	Isolated	—
Voltage - Breakdown	700	V
Frequency - Switching	66, 132	kHz
Power (Watts)	81	W
Duty Cycle	78	%
Operating Temperature	-40 to 150	°C (TJ)
Package / Case	7-SSIP, 6 Leads, Exposed Pad, Formed Leads	—
Supplier Device Package	eSIP-7F	—
Mounting Type	Through Hole	—
Fault Protection	Current Limiting, Over Temperature, Over Voltage	—
Internal Switch(s)	Yes	—
RoHS Status	RoHS Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the TOP255LN is determined by strict equivalence across the following critical parameters:

Mandatory Equivalence Criteria:

Topology: Flyback converter architecture
Output Isolation: Isolated configuration
Voltage - Breakdown: 700V rating
Frequency - Switching: 66kHz and 132kHz operation
Duty Cycle: 78%
Operating Temperature Range: -40°C to 150°C (TJ)
Fault Protection: Current Limiting, Over Temperature, Over Voltage
Internal Switch(s): Integrated switch present
Package / Case: 7-SSIP, 6 Leads, Exposed Pad, Formed Leads
Mounting Type: Through Hole
RoHS Status: RoHS Compliant
MSL: 1 (Unlimited)

Power Rating Consideration: The TOP255LN delivers 81W. Substitute parts are grouped by power output capability. Direct equivalents maintain 81W rating. Parts with different power ratings (21W, 25W, 43W, 62W, 119W) are listed as parametric equivalents within the TOPSwitch®-HX family but require design verification for power budget compatibility.

Package Variant: The TOP255LN uses eSIP-7F package. Active substitutes employ eSIP-7C package variant, which maintains the same 7-SSIP, 6-lead physical footprint and through-hole mounting but represents a packaging evolution within the product line.

Product Status: The TOP255LN is obsolete. All listed substitutes are active products, ensuring long-term availability and supply chain continuity.

Parameter Comparison

Part Number	Manufacturer	Power (W)	Voltage Breakdown (V)	Switching Freq (kHz)	Package	Product Status	Inventory (Pcs)
TOP255LN	Power Integrations	81	700	66, 132	eSIP-7F	Obsolete	1720
TOP255EG	Power Integrations	81	700	66, 132	eSIP-7C	Active	8000
TOP255EN	Power Integrations	81	700	66, 132	eSIP-7C	Active	10037
TOP254EG	Power Integrations	62	700	66, 132	eSIP-7C	Active	16400
TOP254EN	Power Integrations	62	700	66, 132	eSIP-7C	Active	3834
TOP256EG	Power Integrations	119	700	66, 132	eSIP-7C	Active	1266
TOP256EN	Power Integrations	119	700	66, 132	eSIP-7C	Active	27159
TOP253EG	Power Integrations	43	700	66, 132	eSIP-7C	Active	677
TOP253EN	Power Integrations	25	700	66, 132	eSIP-7C	Active	1177
TOP252EG	Power Integrations	21	700	66, 132	eSIP-7C	Active	696
TOP252EN	Power Integrations	21	700	66, 132	eSIP-7C	Active	5100

Engineering Selection Recommendations

Direct Electrical Equivalents (81W Power Rating):

TOP255EG and TOP255EN are direct functional equivalents to TOP255LN. Both maintain the 81W power rating, 700V breakdown voltage, 66kHz/132kHz switching frequency, and identical fault protection architecture. Both are active products with RoHS compliance and unlimited moisture sensitivity rating. TOP255EN offers higher inventory availability (10,037 pcs) compared to TOP255EG (8,000 pcs), supporting supply chain continuity for high-volume applications.

Package Transition:

The transition from eSIP-7F (TOP255LN) to eSIP-7C (TOP255EG, TOP255EN) represents a packaging evolution within the TOPSwitch®-HX family. Both packages maintain 7-SSIP, 6-lead configuration with exposed pad and formed leads, supporting identical through-hole mounting on existing PCB layouts. No circuit redesign is required for package substitution.

Parametric Equivalents (Alternative Power Ratings):

For applications where 81W exceeds power requirements, TOP254EG and TOP254EN (62W) provide lower power alternatives with identical electrical characteristics. TOP256EG and TOP256EN (119W) accommodate higher power demands. TOP253 and TOP252 series parts serve lower power applications (43W, 25W, 21W respectively). Selection among these alternatives depends on application power budget and thermal design margins.

Compliance and Certification:

All substitute parts maintain RoHS compliance, MSL 1 (Unlimited) rating, and identical fault protection features (Current Limiting, Over Temperature, Over Voltage). No additional qualification or testing is required from a regulatory or environmental standpoint.

Frequently Asked Questions (FAQ)

Q: Can TOP255EG or TOP255EN directly replace TOP255LN without PCB modification?

A: Yes. Both TOP255EG and TOP255EN maintain identical electrical specifications (81W, 700V, 66/132kHz, isolated flyback topology) and physical footprint (7-SSIP, 6-lead through-hole package). The eSIP-7C package variant is mechanically compatible with eSIP-7F PCB layouts. No circuit redesign is required.

Q: What is the difference between TOP255EG and TOP255EN?

A: TOP255EG and TOP255EN are functionally identical. Both deliver 81W power, operate at 700V breakdown voltage, and support 66kHz/132kHz switching. The primary distinction is inventory availability: TOP255EN has 10,037 pcs in stock versus TOP255EG with 8,000 pcs. Both are active products with identical compliance certifications.

Q: Can I use TOP254EN (62W) in a design originally specified for TOP255LN (81W)?

A: TOP254EN is a parametric equivalent within the TOPSwitch®-HX family with identical electrical characteristics except power rating. Substitution requires design verification to confirm that 62W output meets application power requirements. Thermal design margins and load current limits must be re-evaluated. This is not a direct drop-in replacement.

Q: Are all substitute parts RoHS compliant?

A: Yes. All listed substitute parts (TOP255EG, TOP255EN, TOP254EG, TOP254EN, TOP256EG, TOP256EN, TOP253EG, TOP253EN, TOP252EG, TOP252EN) are RoHS compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching TOP255LN compliance status.

Q: What fault protection features are included in substitute parts?

A: All substitute parts include identical fault protection: Current Limiting, Over Temperature, and Over Voltage protection. These features are standard across the TOPSwitch®-HX series and ensure equivalent reliability and safety performance.

Q: Is the eSIP-7C package physically compatible with eSIP-7F PCB footprints?

A: Yes. Both eSIP-7C and eSIP-7F packages use 7-SSIP, 6-lead configuration with exposed pad and formed leads. Physical footprint and through-hole mounting are identical, supporting direct PCB compatibility without layout modification.

Q: What is the operating temperature range for substitute parts?

A: All substitute parts operate across -40°C to 150°C junction temperature (TJ), matching TOP255LN specifications. This range supports industrial and consumer applications without thermal derating requirements.

Q: Why is TOP255LN classified as obsolete?

A: TOP255LN is obsolete due to product line evolution. Active equivalents (TOP255EG, TOP255EN) represent the current generation within the TOPSwitch®-HX family, offering improved packaging and supply chain continuity. Existing TOP255LN inventory (1,720 pcs) remains available, but new designs should transition to active alternatives.

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