KBU4K Bridge Rectifier Equivalent & Substitute Parts

Part Overview

The KBU4K is a single-phase bridge rectifier manufactured by onsemi, rated for 800 V peak reverse voltage with 4 A average rectified current. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity. The KBU4K is housed in a 4-SIP through-hole package and operates across a temperature range of -55°C to 150°C.

Key Parameters

Parameter	Value
Diode Type	Single Phase
Technology	Standard
Voltage - Peak Reverse (Max)	800 V
Current - Average Rectified (Io)	4 A
Voltage - Forward (Vf) (Max) @ If	1 V @ 4 A
Operating Temperature	-55°C ~ 150°C (TJ)
Mounting Type	Through Hole
Package / Case	4-SIP

Substitute Part Grouping Explanation

Substitution for the KBU4K is determined by the following critical parameters:

Voltage Rating: All substitutes maintain 800 V peak reverse voltage, ensuring compatibility with the original design voltage specification.
Current Rating: Substitute parts range from 2.8 A to 8 A average rectified current. Parts rated at or above 4 A provide direct functional equivalence; parts with higher ratings offer design margin.
Package Type: All substitutes use 4-SIP through-hole packaging, maintaining mechanical and electrical interface compatibility.
Diode Type & Technology: All substitutes are single-phase standard bridge rectifiers, preserving circuit topology requirements.
Operating Temperature Range: Substitutes operate within or exceed the original -55°C to 150°C range, ensuring thermal compatibility.

Parameter Comparison

Part Number	Manufacturer	Voltage - Peak Reverse (Max)	Current - Average Rectified (Io)	Voltage - Forward (Vf) (Max) @ If	Operating Temperature	Package / Case	Product Status
KBU4K	onsemi	800 V	4 A	1 V @ 4 A	-55°C ~ 150°C	4-SIP, KBU	Obsolete
GBU4K	Diotec Semiconductor	800 V	2.8 A	1 V @ 4 A	-50°C ~ 150°C	4-SIP, GBU	Active
GBU408-G	Comchip Technology	800 V	4 A	1 V @ 2 A	-55°C ~ 150°C	4-SIP, GBU	Active
GBU608-G	Comchip Technology	800 V	6 A	1 V @ 3 A	-55°C ~ 150°C	4-SIP, GBU	Active
GBU808-G	Comchip Technology	800 V	8 A	1 V @ 4 A	-55°C ~ 150°C	4-SIP, GBU	Active
GBU2508-G	Comchip Technology	800 V	4.2 A	1 V @ 12.5 A	-55°C ~ 150°C	4-SIP, GBU	Active

Engineering Selection Recommendations

Direct Equivalent: GBU408-G (Comchip Technology) provides the closest functional match with identical 4 A current rating and matching -55°C to 150°C operating temperature range. This part is actively manufactured and RoHS3 compliant.

Higher Current Margin: GBU2508-G (Comchip Technology) offers 4.2 A rating with enhanced design margin and is RoHS3 compliant. GBU608-G and GBU808-G provide progressively higher current ratings (6 A and 8 A respectively) for applications requiring additional thermal or current headroom.

Lower Current Alternative: GBU4K (Diotec Semiconductor) operates at 2.8 A, which is below the original 4 A specification. This part is suitable only for applications where the actual circuit current demand is confirmed to be below 2.8 A.

All active substitute parts carry RoHS3 compliance and REACH documentation availability, supporting modern regulatory requirements. The KBU4K's obsolete status necessitates migration to one of these active alternatives for new designs and ongoing procurement.

Frequently Asked Questions (FAQ)

Q: Can GBU4K replace KBU4K directly? A: GBU4K is electrically compatible in terms of voltage rating and package type. However, its 2.8 A current rating is below the original 4 A specification. Use only if circuit analysis confirms actual current demand does not exceed 2.8 A.

Q: Which substitute offers the best direct replacement? A: GBU408-G matches the original 4 A current rating and operating temperature range (-55°C to 150°C). It is actively manufactured and RoHS3 compliant.

Q: Are higher-rated parts (GBU608-G, GBU808-G) suitable substitutes? A: Yes. Higher current ratings provide design margin and are fully compatible with the 800 V voltage specification and 4-SIP package. They are appropriate for applications where additional thermal headroom is beneficial.

Q: What is the difference between GBU2508-G and GBU408-G? A: Both are rated at approximately 4 A (4.2 A vs. 4 A). GBU2508-G has a higher forward voltage test current specification (12.5 A vs. 2 A), indicating different characterization conditions. Both are suitable direct replacements.

Q: Are all substitutes RoHS3 compliant? A: Yes. All active substitute parts listed carry RoHS3 compliance certification, meeting current environmental and regulatory standards.

Q: Does package compatibility affect substitution? A: All substitutes use 4-SIP through-hole packaging. While the package designation differs (KBU vs. GBU), the physical form factor and pin configuration are compatible with standard 4-SIP footprints.

Q: What is the temperature range difference between KBU4K and GBU4K? A: KBU4K operates from -55°C to 150°C; GBU4K operates from -50°C to 150°C. The 5°C difference at the lower limit may be significant for applications requiring full -55°C operation.

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