TOP256PG Equivalent & Substitute Parts Reference

Part Overview

The TOP256PG is an offline switch flyback converter IC from Power Integrations' TOPSwitch®-HX series, designed for isolated power supply applications. This component operates at 66 kHz switching frequency with 34 W output power capability and integrated current limiting, over-temperature, and over-voltage protection. The TOP256PG is classified as obsolete; however, equivalent and substitute parts remain available from the same product family to support design continuity and component sourcing requirements.

Key Parameters

Parameter	Value
Manufacturer	Power Integrations
Series	TOPSwitch®-HX
Topology	Flyback
Output Isolation	Isolated
Voltage - Breakdown	700V
Frequency - Switching	66 kHz
Duty Cycle	78%
Power (Watts)	34 W
Fault Protection	Current Limiting, Over Temperature, Over Voltage
Operating Temperature	-40°C ~ 150°C (TJ)
Package / Case	8-DIP (0.300", 7.62mm), 7 Leads
Mounting Type	Through Hole
RoHS Status	RoHS Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution within the TOPSwitch®-HX family is determined by the following critical parameters:

Electrical Compatibility Criteria:

Topology (Flyback)
Output Isolation (Isolated)
Voltage - Breakdown (700V)
Frequency - Switching (66 kHz)
Duty Cycle (78%)
Fault Protection (Current Limiting, Over Temperature, Over Voltage)
Operating Temperature Range (-40°C ~ 150°C)

Mechanical Compatibility Criteria:

Package / Case (8-DIP, 0.300", 7.62mm, 7 Leads)
Mounting Type (Through Hole)
Supplier Device Package (8-PDIP-C)

Substitution Variance: Power output rating (Watts) varies across the family while maintaining identical electrical and mechanical specifications. Parts are grouped by power rating: 15 W (TOP252 series), 25 W (TOP253 series), 28 W (TOP254 series), 30 W (TOP255 series), 34 W (TOP256 series), and 41 W (TOP257 series).

Packaging Variants: Substitute parts are available in two packaging configurations: standard packaging (PG suffix) and tube packaging (PN suffix). Both variants maintain identical electrical and mechanical characteristics.

Parameter Comparison

Part Number	Manufacturer	Product Status	Power (W)	Packaging	Voltage Breakdown	Switching Frequency	Package Type	Inventory (Pcs)
TOP256PG	Power Integrations	Obsolete	34	Standard	700V	66 kHz	8-DIP	1,092
TOP256PN	Power Integrations	Active	34	Tube	700V	66 kHz	8-DIP	19,116
TOP252PG	Power Integrations	Active	15	Standard	700V	66 kHz	8-DIP	968
TOP252PN	Power Integrations	Active	15	Tube	700V	66 kHz	8-DIP	16,771
TOP253PG	Power Integrations	Active	25	Standard	700V	66 kHz	8-DIP	1,025
TOP253PN	Power Integrations	Active	25	Tube	700V	66 kHz	8-DIP	35,300
TOP254PG	Power Integrations	Active	28	Tube	700V	66 kHz	8-DIP	842
TOP254PN	Power Integrations	Active	28	Tube	700V	66 kHz	8-DIP	20,300
TOP255PN	Power Integrations	Active	30	Tube	700V	66 kHz	8-DIP	5,619
TOP257PG	Power Integrations	Active	41	Tube	700V	66 kHz	8-DIP	1,057
TOP257PN	Power Integrations	Active	41	Tube	700V	66 kHz	8-DIP	1,308

Engineering Selection Recommendations

Direct Replacement (Identical Power Rating): TOP256PN is the active-status equivalent of TOP256PG. Both parts deliver 34 W output power with identical electrical and mechanical specifications. TOP256PN is available in tube packaging with significantly higher inventory (19,116 units) compared to TOP256PG (1,092 units). Selection between these two should prioritize TOP256PN due to active product status and superior availability.

Power-Scaled Alternatives: When application requirements permit power rating adjustment, the following active-status alternatives maintain full electrical and mechanical compatibility:

TOP255PN (30 W): Suitable for applications requiring power output below 34 W
TOP254PN (28 W): Suitable for applications requiring power output below 34 W
TOP253PN (25 W): Suitable for applications requiring power output below 34 W
TOP252PN (15 W): Suitable for applications requiring power output below 34 W
TOP257PN (41 W): Suitable for applications requiring power output above 34 W

All alternatives maintain 700V breakdown voltage, 66 kHz switching frequency, 78% duty cycle, identical fault protection features, and -40°C to 150°C operating temperature range.

Compliance and Certification: All substitute parts carry identical RoHS compliance status, REACH unaffected designation, and MSL 1 (Unlimited) moisture sensitivity rating. ECCN and HTSUS classifications remain consistent across the family.

Frequently Asked Questions (FAQ)

Q: Can TOP256PN directly replace TOP256PG in existing designs?

A: Yes. TOP256PN and TOP256PG are electrically and mechanically identical. The primary difference is packaging format (tube versus standard) and product status (active versus obsolete). Both parts operate at 34 W, 700V breakdown, 66 kHz switching frequency, and share the 8-DIP package configuration. PCB layout and circuit design require no modification.

Q: What determines whether a lower-power part (TOP252PN, TOP253PN, TOP254PN, TOP255PN) can substitute for TOP256PG?

A: Power output rating is the only electrical parameter that differs within the TOPSwitch®-HX family. All parts maintain identical topology (flyback), isolation (isolated), breakdown voltage (700V), switching frequency (66 kHz), duty cycle (78%), fault protection features, and operating temperature range. Substitution with lower-power variants is valid only if the application's power requirement does not exceed the substitute part's rating. Circuit design and PCB layout remain unchanged.

Q: Can TOP257PN (41 W) replace TOP256PG (34 W)?

A: Yes, from an electrical and mechanical compatibility standpoint. TOP257PN provides higher power capacity (41 W versus 34 W) while maintaining all other specifications. This substitution is valid if the application can accommodate the higher power rating. No circuit design or PCB layout modifications are required.

Q: What is the difference between PG and PN packaging suffixes?

A: The PG suffix indicates standard packaging; the PN suffix indicates tube packaging. Both variants maintain identical electrical performance and mechanical dimensions (8-DIP, 0.300", 7.62mm, 7 leads). Packaging selection depends on procurement and assembly process requirements. Electrical and thermal characteristics are unchanged.

Q: Are all substitute parts RoHS compliant?

A: Yes. All parts listed in this reference—TOP256PG, TOP256PN, TOP252 series, TOP253 series, TOP254 series, TOP255PN, and TOP257 series—carry RoHS Compliant status. REACH status is unaffected across all variants. MSL rating is 1 (Unlimited) for all parts.

Q: Which substitute part offers the best inventory availability?

A: TOP253PN offers the highest inventory level at 35,300 units. TOP254PN provides 20,300 units, and TOP256PN provides 19,116 units. If power rating flexibility exists in the application, TOP253PN (25 W) represents the most readily available option within the TOPSwitch®-HX family.

Q: Do all parts in this family operate at the same switching frequency?

A: Yes. All listed parts operate at 66 kHz switching frequency with 78% duty cycle. Frequency and duty cycle are fixed parameters across the entire TOPSwitch®-HX family and do not vary by power rating.

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