TOP257LN Equivalent & Substitute Parts Reference

Part Overview

The TOP257LN is an offline switch flyback converter IC manufactured by Power Integrations, part of the TOPSwitch®-HX series. This component operates at 66kHz or 132kHz switching frequency with 105W power output capability and 700V breakdown voltage rating. The part is classified as obsolete, necessitating identification of active equivalent alternatives for new designs and production continuity. Substitute parts must maintain electrical compatibility across isolation topology, switching frequency, voltage ratings, fault protection features, and thermal operating range while accommodating variations in power output levels and packaging designations.

Key Parameters

Parameter	TOP257LN Value	Criticality for Substitution
Manufacturer	Power Integrations	Primary
Series	TOPSwitch®-HX	Primary
Topology	Flyback	Primary
Output Isolation	Isolated	Primary
Voltage - Breakdown	700V	Primary
Frequency - Switching	66kHz, 132kHz	Primary
Duty Cycle	78%	Primary
Fault Protection	Current Limiting, Over Temperature, Over Voltage	Primary
Operating Temperature	-40°C ~ 150°C (TJ)	Primary
Package / Case	7-SSIP, 6 Leads, Exposed Pad, Formed Leads	Secondary
Mounting Type	Through Hole	Secondary
Internal Switch(s)	Yes	Primary
RoHS Status	RoHS Compliant	Secondary
Moisture Sensitivity Level (MSL)	1 (Unlimited)	Secondary

Substitute Part Grouping Explanation

Substitution eligibility for TOP257LN is determined by strict adherence to the following mandatory parameters:

Primary Compatibility Criteria (Non-Negotiable):

Manufacturer: Power Integrations
Series: TOPSwitch®-HX
Topology: Flyback
Output Isolation: Isolated
Voltage - Breakdown: 700V
Frequency - Switching: 66kHz, 132kHz
Duty Cycle: 78%
Fault Protection: Current Limiting, Over Temperature, Over Voltage
Operating Temperature Range: -40°C ~ 150°C (TJ)
Internal Switch(s): Yes

Secondary Compatibility Criteria (Flexible):

Package / Case: 7-SSIP, 6 Leads, Exposed Pad, Formed Leads (eSIP-7C or eSIP-7F variants acceptable)
Mounting Type: Through Hole
RoHS Status: RoHS Compliant
Moisture Sensitivity Level: 1 (Unlimited)

Power Output Variation: Power rating (Watts) is not a constraint for substitution eligibility. Substitute parts with lower power ratings (21W, 25W, 43W, 62W, 81W, 119W) are electrically compatible with the TOP257LN (105W) application, provided all primary criteria are met. Selection of specific power rating depends on application requirements.

All substitute parts listed are from the Power Integrations TOPSwitch®-HX family and share identical electrical architecture, protection mechanisms, and thermal characteristics with the TOP257LN.

Parameter Comparison

Part Number	Manufacturer	Series	Topology	Isolation	Breakdown Voltage	Switching Frequency	Duty Cycle	Power (W)	Operating Temp	Product Status	Inventory (Pcs)
TOP257LN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	105	-40°C ~ 150°C	Obsolete	2100
TOP252EG	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	21	-40°C ~ 150°C	Active	696
TOP252EN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	21	-40°C ~ 150°C	Active	5100
TOP253EG	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	43	-40°C ~ 150°C	Active	677
TOP253EN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	25	-40°C ~ 150°C	Active	1177
TOP254EG	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	62	-40°C ~ 150°C	Active	16400
TOP254EN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	62	-40°C ~ 150°C	Active	3834
TOP255EG	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	81	-40°C ~ 150°C	Active	8000
TOP255EN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	81	-40°C ~ 150°C	Active	10037
TOP256EG	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	119	-40°C ~ 150°C	Active	1266
TOP256EN	Power Integrations	TOPSwitch®-HX	Flyback	Isolated	700V	66kHz, 132kHz	78%	119	-40°C ~ 150°C	Active	27159

Engineering Selection Recommendations

Product Status Consideration: The TOP257LN is classified as obsolete. All listed substitute parts are active products with ongoing manufacturing and support from Power Integrations. Selection of active alternatives ensures long-term supply chain stability and access to technical documentation.

Compliance and Certification: All substitute parts maintain identical compliance certifications to the TOP257LN:

RoHS Compliant
REACH Unaffected
ECCN: EAR99
HTSUS: 8542.39.0001
Moisture Sensitivity Level: 1 (Unlimited)

Packaging Designation: The TOP257LN uses eSIP-7F packaging. Substitute parts employ eSIP-7C packaging. Both designations represent 7-SSIP, 6 Leads with Exposed Pad and Formed Leads in through-hole mounting configuration. Mechanical and electrical compatibility is maintained across these packaging variants within the TOPSwitch®-HX series.

Power Rating Selection: For applications currently using TOP257LN (105W), substitute parts with equal or higher power ratings are directly compatible:

TOP256EG (119W) or TOP256EN (119W) provide equivalent or superior capability
Parts with lower power ratings (TOP252 through TOP255 series) are electrically compatible but may require thermal design review for applications demanding full 105W output

Inventory Availability: TOP256EN demonstrates highest inventory availability (27,159 pcs), followed by TOP254EG (16,400 pcs) and TOP255EN (10,037 pcs). These options provide optimal supply chain flexibility for production planning.

Frequently Asked Questions (FAQ)

Q: Can TOP252EN substitute for TOP257LN in a 105W application? A: TOP252EN is electrically compatible with TOP257LN across all primary parameters (topology, isolation, voltage, frequency, protection, temperature range). However, TOP252EN is rated for 21W output. Substitution is valid from an electrical standpoint, but thermal design must accommodate the lower power rating specification. Application power requirements determine practical suitability.

Q: What is the difference between TOP254EG and TOP254EN? A: Both parts are identical in electrical specifications (62W, 700V, 66kHz/132kHz,

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