3KP28-B Equivalent & Substitute Parts

Part Overview

The 3KP28-B is a unidirectional Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. Rated at 28V reverse standoff voltage with a 47.67V maximum clamping voltage and 66.1A peak pulse current, this component provides 3kW peak pulse power dissipation in a through-hole P600 axial package. The part is currently obsolete, necessitating identification of functionally equivalent alternatives from active product lines that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	28V
Voltage - Breakdown (Min)	29.48V
Voltage - Clamping (Max) @ Ipp	47.67V
Current - Peak Pulse (10/1000µs)	66.1A
Power - Peak Pulse	3000W (3kW)
Operating Temperature Range	-55°C ~ 175°C (TJ)
Mounting Type	Through Hole
Package / Case	P600, Axial
Type	Zener
Unidirectional Channels	1
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 3KP28-B is determined by the following critical parameters:

Mandatory Matching Criteria:

Voltage - Reverse Standoff: 28V (exact match required)
Type: Zener, Unidirectional (1 channel)
Operating Temperature Range: -55°C ~ 175°C minimum
RoHS Status: ROHS3 Compliant
Mounting Type: Through Hole
Applications: General Purpose

Allowable Variation Criteria:

Voltage - Clamping (Max) @ Ipp: 45.4V to 50V (within acceptable overvoltage protection envelope)
Current - Peak Pulse: 66.1A minimum (higher values acceptable for enhanced transient handling)
Power - Peak Pulse: 3kW minimum (higher ratings acceptable)
Package / Case: P600 or R-6 axial packages (both through-hole compatible)
Manufacturer: Multiple qualified sources acceptable

Substitute parts must maintain the 28V standoff voltage specification and general-purpose protection function while accommodating variations in clamping voltage, peak current capacity, and power dissipation within the defined ranges. Package compatibility is confirmed for both P600 and R-6 axial through-hole formats.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff	Voltage - Breakdown (Min)	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse (10/1000µs)	Power - Peak Pulse	Package / Case	Product Status
3KP28-B	Littelfuse Inc.	28V	29.48V	47.67V	66.1A	3000W	P600, Axial	Obsolete
5KP28A-B	Littelfuse Inc.	28V	31.1V	45.4V	112.3A	5000W	P600, Axial	Active
3KP28A-TP	Micro Commercial Co	28V	31.1V	45.4V	—	3000W	R-6, Axial	Active
15KP28A-TP	Micro Commercial Co	28V	31.1V	47.5V	—	15000W	R-6, Axial	Active
15KPA28AE3/TR13	Microchip Technology	28V	31.28V	47.5V	317.9A	15000W	P600, Axial	Active
15KPA28E3/TR13	Microchip Technology	28V	29.48V	—	—	15000W	P600, Axial	Active
30KP28A-TP	Micro Commercial Co	28V	31.28V	50V	—	30000W	R-6, Axial	Active
5KP28A-E3/54	Vishay General Semiconductor - Diodes Division	28V	31.1V	45.4V	110A	5000W	P600, Axial	Active
5KP28AHE3/54	Vishay General Semiconductor - Diodes Division	28V	31.1V	45.4V	110A	5000W	P600, Axial	Active
5KP28AHE3/73	Vishay General Semiconductor - Diodes Division	28V	31.1V	45.4V	110A	5000W	P600, Axial	Active

Engineering Selection Recommendations

Direct Replacement (Same Power Rating): The 3KP28A-TP from Micro Commercial Co provides equivalent 3kW peak pulse power dissipation with matching 28V standoff voltage. This part is active and ROHS3 compliant. The R-6 axial package is mechanically compatible with through-hole PCB layouts designed for the original P600 package. This option maintains the original power specification while transitioning to an active product line.

Enhanced Protection (Higher Power Rating): The 5KP28A-B from Littelfuse Inc., 5KP28A-E3/54 from Vishay, and 5KP28AHE3 variants from Vishay offer 5kW peak pulse power with identical 28V standoff voltage and P600 package compatibility. These parts provide increased transient current handling (110A to 112.3A) and are suitable for applications requiring enhanced overvoltage margin. All variants are active and ROHS3 compliant.

Maximum Protection (Highest Power Rating): The 15KPA28AE3/TR13 from Microchip Technology and 15KP28A-TP from Micro Commercial Co deliver 15kW peak pulse power with 28V standoff voltage. The Microchip part maintains P600 package compatibility with 317.9A peak pulse current. The Micro Commercial part uses R-6 package. These options are appropriate for high-energy transient environments and are active with ROHS3 compliance.

Automotive Grade Option: The 5KP28AHE3/54 and 5KP28AHE3/73 from Vishay are AEC-Q101 qualified automotive-grade variants with identical electrical specifications to standard 5KP28A-E3/54. These are suitable for automotive and harsh-environment applications requiring automotive qualification.

All recommended substitutes maintain ROHS3 compliance, -55°C to 175°C operating temperature range, and general-purpose application suitability.

Frequently Asked Questions (FAQ)

Q: Can I use a higher power-rated TVS diode as a direct substitute? A: Yes. Higher power ratings (5kW, 15kW, 30kW) are acceptable substitutes provided the 28V reverse standoff voltage, Zener type, unidirectional configuration, and through-hole mounting are maintained. Higher power ratings provide enhanced transient protection capability without compromising circuit function.

Q: Are P600 and R-6 packages interchangeable? A: Both P600 and R-6 are axial through-hole packages suitable for standard PCB layouts. They are mechanically compatible for through-hole mounting applications. Verify PCB pad spacing and lead length requirements for your specific design.

Q: What is the difference between standard and automotive-grade variants? A: Automotive-grade parts (5KP28AHE3/54, 5KP28AHE3/73) carry AEC-Q101 qualification, indicating compliance with automotive reliability and testing standards. These are required for automotive applications but are functionally equivalent to standard variants for general-purpose use.

Q: Does clamping voltage variation affect substitutability? A: Clamping voltage variations within the 45.4V to 50V range are acceptable. The original 3KP28-B specifies 47.67V maximum clamping. Substitute parts with 45.4V to 50V clamping maintain effective overvoltage suppression within the design envelope. Verify your circuit's maximum allowable clamping voltage requirement.

Q: Why is the 3KP28-B obsolete? A: The part is no longer manufactured by Littelfuse Inc. Active alternatives from multiple manufacturers provide equivalent or enhanced functionality and are recommended for new designs and production continuity.

Q: Can I substitute with a different voltage rating? A: No. The 28V reverse standoff voltage is a critical parameter. Substitutes must maintain exactly 28V standoff voltage. Parts with different voltage ratings (e.g., 24V, 30V) are not compatible and will not provide correct overvoltage protection.

Q: What certifications should I verify for my application? A: All listed substitutes are ROHS3 compliant. For automotive applications, specify AEC-Q101 qualified variants (5KP28AHE3 series). Verify REACH compliance status if required by your supply chain or regulatory requirements.

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