3KP85A Equivalent & Substitute Parts

Part Overview

The 3KP85A is a unidirectional Transient Voltage Suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose transient voltage protection applications. This component features an 85V reverse standoff voltage with a 137V maximum clamping voltage and 21.9A peak pulse current capability at 3000W peak pulse power dissipation. The 3KP85A is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	85V
Voltage - Breakdown (Min)	94.4V
Voltage - Clamping (Max) @ Ipp	137V
Current - Peak Pulse (10/1000µs)	21.9A
Power - Peak Pulse	3000W
Operating Temperature Range	-55°C ~ 175°C (TJ)
Mounting Type	Through Hole
Package / Case	P600, Axial
Type	Zener
Unidirectional Channels	1

Substitute Part Grouping Explanation

Substitution for the 3KP85A is determined by the following critical parameters:

Voltage - Reverse Standoff: 85V (exact match required)
Voltage - Clamping (Max) @ Ipp: 137V (exact match required)
Voltage - Breakdown (Min): 94.4V (exact match required)
Type: Zener, Unidirectional (1 channel)
Mounting Type: Through Hole, Axial package orientation
Operating Temperature Range: Minimum -55°C to 175°C capability

Substitute parts are grouped into two categories:

Category 1: Direct Electrical Equivalents (Same Power Rating) Parts maintaining the 3000W peak pulse power specification with identical voltage parameters and compatible package footprints.

Category 2: Enhanced Performance Substitutes (Higher Power Rating) Parts with identical voltage parameters but increased peak pulse current (36A–36.5A) and 5000W peak pulse power capability, offering superior transient suppression margin while maintaining electrical compatibility.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse	Power - Peak Pulse	Operating Temperature	Package / Case	Product Status
3KP85A	Littelfuse Inc.	85V	137V	21.9A	3000W	-55°C ~ 175°C	P600, Axial	Obsolete
3KP85A-TP	Micro Commercial Co	85V	137V	21.9A	3000W	-55°C ~ 175°C	R-6, Axial	Active
5KP85A	Diotec Semiconductor	85V	137V	36A	5000W	-50°C ~ 175°C	P600, Axial	Active
5KP85A-E3/54	Vishay General Semiconductor - Diodes Division	85V	137V	36.5A	5000W	-55°C ~ 175°C	P600, Axial	Active
5KP85A-E3/73	Vishay General Semiconductor - Diodes Division	85V	137V	36.5A	5000W	-55°C ~ 175°C	P600, Axial	Active
5KP85AHE3/54	Vishay General Semiconductor - Diodes Division	85V	137V	36.5A	5000W	-55°C ~ 175°C	P600, Axial	Active

Engineering Selection Recommendations

For Direct Replacement (Identical Specifications): The 3KP85A-TP from Micro Commercial Co is the primary direct substitute, maintaining identical electrical specifications (21.9A peak pulse current, 3000W power dissipation) and operating temperature range (-55°C ~ 175°C). This part is currently active and ROHS3 compliant. Package variation (R-6 vs. P600) requires mechanical verification for PCB footprint compatibility.

For Enhanced Performance Applications: The 5KP85A-E3/54 and 5KP85AHE3/54 from Vishay General Semiconductor offer superior transient suppression capability with 36.5A peak pulse current and 5000W power dissipation while maintaining identical voltage parameters. Both parts are ROHS3 compliant and support the full -55°C ~ 175°C operating temperature range. The 5KP85AHE3/54 includes AEC-Q101 automotive qualification for applications requiring automotive-grade reliability.

For Standard Industrial Applications: The 5KP85A-E3/73 from Vishay General Semiconductor provides equivalent enhanced performance specifications with active product status and ROHS3 compliance.

For Cost-Optimized Procurement: The 5KP85A from Diotec Semiconductor offers enhanced performance (36A, 5000W) at potentially lower cost, with the trade-off of a reduced lower operating temperature limit (-50°C vs. -55°C).

Frequently Asked Questions (FAQ)

Q: Can the 5KP85A series parts directly replace the 3KP85A? A: Yes, electrically. All 5KP85A variants maintain the required 85V reverse standoff and 137V clamping voltages. The higher peak pulse current (36–36.5A) and power rating (5000W) provide enhanced protection margin. Package footprint compatibility must be verified; P600 packages are mechanically identical, while R-6 packages require PCB layout confirmation.

Q: What is the difference between 5KP85A-E3/54, 5KP85A-E3/73, and 5KP85AHE3/54? A: All three parts share identical electrical specifications (85V standoff, 137V clamp, 36.5A peak pulse, 5000W power). The designations reflect different packaging configurations and qualification levels. The 5KP85AHE3/54 includes AEC-Q101 automotive qualification; the others are standard industrial-grade components.

Q: Is the 3KP85A-TP a true equivalent? A: Yes. The 3KP85A-TP maintains identical electrical performance (21.9A, 3000W, -55°C ~ 175°C). The package designation changes from P600 to R-6, requiring mechanical compatibility verification with the PCB design.

Q: Why would I choose a higher-power 5KP85A over the 3KP85A-TP equivalent? A: Enhanced performance substitutes provide greater transient suppression margin and improved reliability in high-stress applications. The 5KP85A series handles 64% higher peak pulse current and 67% higher power dissipation, reducing component stress and extending service life.

Q: Are all substitute parts ROHS3 compliant? A: Yes. All listed substitute parts carry ROHS3 compliance certification, meeting environmental and hazardous substance restrictions.

Q: What is the operating temperature consideration for the 5KP85A from Diotec? A: The Diotec 5KP85A operates from -50°C to 175°C, compared to -55°C for other substitutes. This 5°C lower limit may be significant for applications requiring full -55°C cold-start performance.

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