TOP258LG Equivalent & Substitute Parts

Part Overview

The TOP258LG 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 a maximum power rating of 122W and features integrated current limiting, over-temperature, and over-voltage protection. The device is classified as obsolete, necessitating identification of active equivalent alternatives for new designs and production continuity. Substitute parts must maintain electrical compatibility across voltage breakdown, topology, switching frequency, duty cycle, and thermal operating range while accommodating variations in power output and packaging designations.

Key Parameters

Parameter	TOP258LG Value	Criticality for Substitution
Manufacturer	Power Integrations	Required Match
Series	TOPSwitch®-HX	Required Match
Topology	Flyback	Required Match
Voltage - Breakdown	700V	Required Match
Frequency - Switching	66kHz, 132kHz	Required Match
Duty Cycle	78%	Required Match
Output Isolation	Isolated	Required Match
Internal Switch(s)	Yes	Required Match
Fault Protection	Current Limiting, Over Temperature, Over Voltage	Required Match
Operating Temperature	-40°C ~ 150°C (TJ)	Required Match
Package / Case	7-SSIP, 6 Leads, Exposed Pad, Formed Leads	Required Match
Mounting Type	Through Hole	Required Match
Power (Watts)	122W	Application-Dependent
RoHS Status	RoHS Compliant	Regulatory Requirement
Product Status	Obsolete	Substitution Driver

Substitute Part Grouping Explanation

Substitution of the TOP258LG is determined by strict adherence to the following electrical and mechanical parameters:

Required Matching Parameters:

Manufacturer: Power Integrations
Series: TOPSwitch®-HX
Topology: Flyback
Voltage - Breakdown: 700V
Switching Frequency: 66kHz, 132kHz
Duty Cycle: 78%
Output Isolation: Isolated
Internal Switch(s): Yes
Fault Protection: Current Limiting, Over Temperature, Over Voltage
Operating Temperature Range: -40°C ~ 150°C (TJ)
Package / Case: 7-SSIP, 6 Leads, Exposed Pad, Formed Leads
Mounting Type: Through Hole
RoHS Compliance: RoHS Compliant

Variable Parameter (Application-Dependent):

Power (Watts): Substitute parts range from 21W to 119W. Selection depends on circuit power requirements. The TOP258LG at 122W can be substituted with parts rated at equal or higher power output.

All substitute parts listed are active products with current manufacturing status, ensuring long-term availability and supply chain continuity.

Parameter Comparison

Part Number	Manufacturer	Series	Topology	Voltage Breakdown	Switching Frequency	Duty Cycle	Power (W)	Operating Temp (°C)	Package	Product Status	Inventory (Pcs)
TOP258LG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	122	-40 ~ 150	7-SSIP	Obsolete	664
TOP252EG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	21	-40 ~ 150	7-SSIP	Active	696
TOP252EN	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	21	-40 ~ 150	7-SSIP	Active	5100
TOP253EG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	43	-40 ~ 150	7-SSIP	Active	677
TOP253EN	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	25	-40 ~ 150	7-SSIP	Active	1177
TOP254EG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	62	-40 ~ 150	7-SSIP	Active	16400
TOP254EN	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	62	-40 ~ 150	7-SSIP	Active	3834
TOP255EG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	81	-40 ~ 150	7-SSIP	Active	8000
TOP255EN	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	81	-40 ~ 150	7-SSIP	Active	10037
TOP256EG	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	119	-40 ~ 150	7-SSIP	Active	1266
TOP256EN	Power Integrations	TOPSwitch®-HX	Flyback	700V	66kHz, 132kHz	78%	119	-40 ~ 150	7-SSIP	Active	27159

Engineering Selection Recommendations

Primary Substitution Candidates:

For applications requiring power output at or above 122W, TOP256EG and TOP256EN are the direct electrical equivalents, each rated at 119W. Both parts are active products with full manufacturing support. TOP256EN offers superior inventory availability (27,159 units) compared to TOP256EG (1,266 units), providing enhanced supply chain reliability.

Secondary Substitution Candidates:

For applications with lower power requirements, the following active alternatives maintain full electrical and mechanical compatibility:

TOP255EG / TOP255EN (81W): Suitable for designs requiring 81W maximum output
TOP254EG / TOP254EN (62W): Suitable for designs requiring 62W maximum output
TOP253EG / TOP253EN (43W / 25W): Suitable for designs requiring lower power outputs
TOP252EG / TOP252EN (21W): Suitable for minimal power requirement applications

Compliance and Regulatory Status:

All substitute parts maintain RoHS compliance and REACH unaffected status, matching the regulatory profile of the TOP258LG. Moisture sensitivity level (MSL) is 1 (Unlimited) across all alternatives, indicating no special handling requirements during storage or assembly.

Product Status Consideration:

The TOP258LG is classified as obsolete. All listed substitute parts are active products with current manufacturing status, ensuring continued availability for new production runs and design revisions.

Frequently Asked Questions (FAQ)

Q1: Can TOP256EN directly replace TOP258LG in existing designs?

TOP256EN maintains electrical equivalence across all critical parameters: 700V breakdown voltage, 66kHz/132kHz switching frequency, 78% duty cycle, isolated output, and identical fault protection features. The 7-SSIP package and through-hole mounting are identical. The 119W power rating of TOP256EN accommodates the 122W requirement of TOP258LG. Direct substitution is electrically valid without circuit modification.

Q2: What is the difference between TOP256EG and TOP256EN?

Both TOP256EG and TOP256EN are identical in electrical specifications and package configuration. The suffix designates packaging format: EG indicates tube packaging, while EN indicates alternative packaging. Selection between these variants depends on procurement and assembly line requirements. TOP256EN offers significantly higher inventory availability.

Q3: Can lower-power alternatives such as TOP254EN substitute for TOP258LG?

TOP254EN is electrically compatible across all parameters except power output. TOP254EN is rated at 62W, while TOP258LG is rated at 122W. Substitution is valid only if the application circuit requires 62W or less. Using an undersized power rating in a higher-power application will result in thermal stress and potential device failure.

Q4: Are all substitute parts RoHS compliant?

All substitute parts listed are RoHS compliant and REACH unaffected, matching the regulatory status of TOP258LG. No additional compliance documentation is required for substitution.

Q5: What is the operating temperature range for substitute parts?

All substitute parts operate across the identical temperature range: -40°C to +150°C (junction temperature). Thermal management requirements remain unchanged from the original TOP258LG design.

Q6: Do substitute parts require PCB layout modifications?

All substitute parts use the 7-SSIP package with 6 leads, exposed pad, and formed leads. The mechanical footprint and pin configuration are identical to TOP258LG. Existing PCB layouts require no modification for component substitution.

Q7: Which substitute part offers the best supply chain availability?

TOP256EN provides the highest inventory level at 27,159 units, followed by TOP254EG at 16,400 units and TOP255EN at 10,037 units. For long-term production continuity, TOP256EN is the recommended choice.

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