KA3842B Equivalent & Substitute Parts

Part Overview

The KA3842B is an offline switch IC manufactured by onsemi, designed for power management applications in converter topologies operating up to 500kHz. This 8-DIP through-hole component functions as a frequency-controlled power management IC with a 97% duty cycle and supply voltage range of 12V to 25V. The KA3842B is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements.

Substiute Parts

KA3842B

onsemiIn Stock: 13563KA3842B Datasheet

Current PartRFQ

UC3842BNG

onsemiIn Stock: 2438UC3842BNG Datasheet

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LT1246CN8#PBF

Analog Devices Inc.In Stock: 801LT1246CN8#PBF Datasheet

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TL3842BP

Texas InstrumentsIn Stock: 1470TL3842BP Datasheet

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TL3842P

Texas InstrumentsIn Stock: 24398TL3842P Datasheet

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UC3842AN

onsemiIn Stock: 89007UC3842AN Datasheet

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UC3842BN

STMicroelectronicsIn Stock: 55131UC3842BN Datasheet

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UC3842N

onsemiIn Stock: 2331UC3842N Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution for the KA3842B is determined by strict alignment of the following critical parameters:

Primary Substitution Criteria:

• Package / Case: 8-DIP (0.300", 7.62mm) form factor
• Mounting Type: Through Hole
• Voltage - Supply (Vcc/Vdd): Minimum 10V to 30V range (encompasses KA3842B's 12V ~ 25V requirement)
• Frequency - Switching: Up to 500kHz capability
• Control Features: Frequency Control
• Operating Temperature: 0°C ~ 70°C minimum range

Secondary Compatibility Factors:

• Duty Cycle: Maximum 96% or higher
• Topology: Offline switch, boost, or flyback configurations
• REACH and ECCN compliance status

Substitute parts meeting these criteria maintain functional and mechanical compatibility with the KA3842B in offline switch and converter applications.

Parameter Comparison

Engineering Selection Recommendations

Preferred Active Substitutes:

UC3842BNG (onsemi) and TL3842P (Texas Instruments) are the primary recommended substitutes. Both maintain active product status, ROHS3 compliance, and full parameter compatibility with the KA3842B. UC3842BNG offers the same manufacturer lineage as the original part, while TL3842P provides broader supply availability with 24,348 units in stock.

Secondary Active Substitute:

UC3842BN (STMicroelectronics) is an active product with ROHS3 compliance and 55,100 units in inventory. This part meets all electrical and mechanical substitution criteria and represents a viable alternative for high-volume applications.

Extended Temperature Range Option:

LT1246CN8#PBF (Analog Devices Inc.) extends the operating temperature range to 0°C ~ 100°C and supports switching frequencies up to 1MHz. This part is suitable for applications requiring enhanced thermal performance, though it operates in a buck topology rather than the offline switch topology of the KA3842B.

Obsolete Status Alternatives:

UC3842AN and UC3842N are classified as obsolete. While these parts meet substitution criteria, they should be considered only when active alternatives are unavailable. UC3842AN maintains RoHS non-compliance status, which may conflict with modern regulatory requirements.

Last Time Buy Consideration:

TL3842BP (Texas Instruments) carries Last Time Buy status. This designation indicates limited future availability and should be selected only when other active alternatives are unsuitable for the application.

Frequently Asked Questions (FAQ)

Q: Can I use UC3842BNG as a direct replacement for KA3842B?

A: Yes. UC3842BNG matches all critical substitution parameters: 8-DIP package, through-hole mounting, 10V ~ 30V supply voltage range (encompassing KA3842B's 12V ~ 25V), up to 500kHz switching frequency, and frequency control features. UC3842BNG is active and ROHS3 compliant.

Q: What is the difference between TL3842BP and TL3842P?

A: Both parts are manufactured by Texas Instruments in 8-DIP packages with identical electrical specifications. TL3842BP carries Last Time Buy status with 1,392 units available, while TL3842P is active with 24,348 units in stock. For new designs, TL3842P is preferred due to active status and higher availability.

Q: Why does LT1246CN8#PBF have a higher switching frequency specification?

A: LT1246CN8#PBF supports up to 1MHz switching frequency compared to the KA3842B's 500kHz maximum. This higher frequency capability does not prevent substitution; the part remains compatible with applications designed for 500kHz operation. The extended temperature range (0°C ~ 100°C) and buck topology represent the primary functional differences.

Q: Are all substitute parts ROHS3 compliant?

A: No. UC3842AN is RoHS non-compliant. All other listed substitutes (UC3842BNG, LT1246CN8#PBF, TL3842BP, TL3842P, UC3842BN) are ROHS3 compliant. For applications requiring RoHS compliance, avoid UC3842AN.

Q: What does "Last Time Buy" status mean for TL3842BP?

A: Last Time Buy indicates that Texas Instruments has announced the end of production for this part. Existing inventory may be available, but future procurement cannot be guaranteed. For new designs requiring long-term component availability, select active alternatives such as TL3842P or UC3842BNG.

Q: Can I substitute KA3842B with UC3842N?

A: UC3842N meets all electrical and mechanical substitution criteria. However, UC3842N is classified as obsolete, and only 2,300 units are in inventory. This part should be selected only when active alternatives are unavailable or when existing designs are locked to this specific part number.

Q: Do all substitute parts support the same duty cycle as KA3842B?

A: The KA3842B specifies 97% duty cycle. Most substitutes support 96% maximum duty cycle (UC3842BNG, TL3842BP, UC3842AN, UC3842BN), while TL3842P matches 97% and LT1246CN8#PBF supports 100%. All values are sufficient for offline switch and converter applications designed for the KA3842B.