KA3845B Equivalent & Substitute Parts

Part Overview

The KA3845B 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 supply controller. The part is currently obsolete, making equivalent substitutes necessary for new designs, repairs, and production continuity. Substitute parts must maintain compatibility across voltage supply ranges, switching frequency capabilities, duty cycle specifications, and package form factors.

Substiute Parts

KA3845B

onsemiIn Stock: 2144KA3845B Datasheet

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UC3845BNG

onsemiIn Stock: 2536UC3845BNG Datasheet

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SG3845M

Microchip TechnologyIn Stock: 4908SG3845M Datasheet

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TL3845BP

Texas InstrumentsIn Stock: 1170TL3845BP Datasheet

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TL3845P

Texas InstrumentsIn Stock: 125497TL3845P Datasheet

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UC2845BN

STMicroelectronicsIn Stock: 2001UC2845BN Datasheet

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UC3845AN

Texas InstrumentsIn Stock: 88794UC3845AN Datasheet

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UC3845BN

STMicroelectronicsIn Stock: 88892UC3845BN Datasheet

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UC3845N

onsemiIn Stock: 20465UC3845N Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution compatibility for the KA3845B is determined by the following critical parameters:

Physical Compatibility: All substitute parts must use the 8-DIP (0.300", 7.62mm) package with through-hole mounting to ensure direct PCB compatibility without layout modifications.

Electrical Compatibility: Substitute parts must support:

• Voltage supply range of 7.6V ~ 30V (encompasses the KA3845B operating range of 12V ~ 25V)
• Switching frequency capability up to 500kHz
• Maximum duty cycle of 48%
• Frequency control feature

Functional Compatibility: Substitute parts must function as power supply controllers with transistor driver output capability, supporting boost, flyback, or forward converter topologies.

Seven substitute parts meet these criteria: UC3845BNG, SG3845M, TL3845BP, TL3845P, UC2845BN, UC3845AN, UC3845BN, and UC3845N.

Parameter Comparison

Engineering Selection Recommendations

For New Designs: Select from active product status parts with ROHS3 compliance. UC3845BNG, SG3845M, TL3845BP, TL3845P, UC2845BN, UC3845AN, and UC3845BN all meet these criteria. UC3845BNG and UC3845BN offer the broadest switching frequency range (up to 500kHz) matching the KA3845B specification.

For Extended Temperature Range Applications: UC2845BN and UC3845BN support -40°C ~ 150°C operating temperature, exceeding the KA3845B range of 0°C ~ 70°C.

For Automotive Applications: TL3845P carries AEC-Q100 qualification and automotive grade designation, suitable for automotive power supply designs.

For Legacy System Repairs: UC3845N maintains onsemi manufacturer continuity but is obsolete. UC3845BN (STMicroelectronics) or UC3845BNG (onsemi) provide active alternatives with identical electrical specifications.

Compliance Consideration: All recommended substitutes except UC3845N are ROHS3 compliant, meeting current environmental regulations.

Frequently Asked Questions (FAQ)

Q: Can I directly replace KA3845B with any of these substitutes without PCB modifications?

A: Yes, all listed substitutes use the same 8-DIP (0.300", 7.62mm) through-hole package. Pin-to-pin compatibility is maintained across all substitute parts, allowing direct socket replacement.

Q: What is the primary reason the KA3845B is obsolete?

A: The KA3845B is marked obsolete by the manufacturer. Active alternatives with identical or superior electrical specifications are available from multiple manufacturers, ensuring design continuity and supply chain reliability.

Q: Which substitute offers the closest electrical match to KA3845B?

A: UC3845BNG, UC3845BN, and UC3845N provide identical electrical specifications: 7.6V ~ 30V supply voltage, up to 500kHz switching frequency, 48% maximum duty cycle, and frequency control features. UC3845BNG and UC3845BN are active products with ROHS3 compliance.

Q: Are there temperature range differences I should consider?

A: The KA3845B operates 0°C ~ 70°C. UC2845BN and UC3845BN extend this to -40°C ~ 150°C, providing wider operating margins for industrial or automotive environments. Other substitutes maintain the 0°C ~ 70°C range.

Q: Does switching frequency specification affect substitution?

A: TL3845BP and TL3845P specify 100kHz fixed switching frequency, while KA3845B and most other substitutes support up to 500kHz. For designs requiring variable or higher switching frequencies, select UC3845BNG, SG3845M, UC2845BN, UC3845BN, or UC3845N.

Q: What compliance certifications should I verify for new designs?

A: All active substitutes except UC3845N are ROHS3 compliant. TL3845P additionally carries AEC-Q100 automotive qualification. Verify REACH compliance status with your supplier for your specific application requirements.

Q: Can I use UC3845N as a substitute despite its obsolete status?

A: UC3845N is functionally equivalent but shares obsolete status with KA3845B. For long-term supply assurance, select active alternatives: UC3845BNG, UC3845BN, UC2845BN, or TL3845BP.