3KP78-B Equivalent & Substitute Parts

Part Overview

The 3KP78-B is a unidirectional Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. Rated at 78V reverse standoff voltage with a 132.3V maximum clamping voltage and 23.8A peak pulse current, this component operates across the temperature range of -55°C to 175°C in a P600 axial through-hole package. The product is currently obsolete, necessitating identification of functionally equivalent alternatives from active product lines to maintain design continuity and ensure supply chain availability.

Substiute Parts

3KP78-B

Littelfuse Inc.In Stock: 8333KP78-B Datasheet

Current PartRFQ

5KP78A-B

Littelfuse Inc.In Stock: 8895KP78A-B Datasheet

DirectRFQ

15KPA78AE3/TR13

Microchip TechnologyIn Stock: 99815KPA78AE3/TR13 Datasheet

MFR RecommendedRFQ

5KP78A-E3/54

Vishay General Semiconductor - Diodes DivisionIn Stock: 82855KP78A-E3/54 Datasheet

MFR RecommendedRFQ

5KP78AHE3/54

Vishay General Semiconductor - Diodes DivisionIn Stock: 10625KP78AHE3/54 Datasheet

MFR RecommendedRFQ

5KP78AHE3/73

Vishay General Semiconductor - Diodes DivisionIn Stock: 10165KP78AHE3/73 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 3KP78-B is determined by strict equivalence across the following critical parameters:

• Voltage Rating: Reverse standoff voltage of 78V and breakdown voltage minimum of 82.13V
• Package Type: P600 axial through-hole configuration
• Diode Type: Unidirectional Zener TVS
• Operating Temperature Range: -55°C to 175°C
• Compliance: ROHS3 compliance and general-purpose application classification

Substitute parts must maintain identical voltage specifications and package geometry to ensure direct circuit compatibility. Peak pulse current and power ratings may vary within the same voltage class, as higher-rated alternatives provide enhanced transient suppression capability without compromising circuit protection thresholds.

Parameter Comparison

Engineering Selection Recommendations

All listed substitute parts maintain electrical equivalence with the 3KP78-B across the critical voltage and temperature parameters required for direct circuit replacement. Selection among active alternatives should be based on the following criteria:

Standard Industrial Applications: The 5KP78A-B from Littelfuse Inc. provides a direct manufacturer alternative with active product status, maintaining the same supplier relationship and supply chain continuity. This part offers increased peak pulse current (40.5A) and power rating (5kW) compared to the obsolete 3KP78-B.

Enhanced Transient Protection: The 15KPA78AE3/TR13 from Microchip Technology delivers significantly higher peak pulse current (119.7A) and power dissipation (15kW), suitable for applications requiring superior transient suppression capability within the same voltage class.

Automotive and Reliability-Critical Applications: The 5KP78AHE3/54 and 5KP78AHE3/73 from Vishay General Semiconductor are qualified to AEC-Q101 automotive standards, appropriate for automotive and mission-critical environments. Both variants maintain identical electrical specifications with 5kW power rating and 39.7A peak pulse current.

Supply Chain Flexibility: The 5KP78A-E3/54 from Vishay General Semiconductor offers active status with Cut Tape packaging, providing alternative sourcing and packaging options while maintaining full electrical equivalence.

All substitute parts are ROHS3 compliant and operate across the identical temperature range (-55°C to 175°C), ensuring compatibility with existing thermal design requirements.

Frequently Asked Questions (FAQ)

Q: Can the 3KP78-B be directly replaced with any of the listed substitutes?

A: Yes. All listed substitute parts share identical voltage ratings (78V reverse standoff), breakdown characteristics, and P600 axial through-hole package geometry. Direct circuit replacement is supported without design modification.

Q: What is the significance of the higher peak pulse current ratings in substitute parts?

A: Substitute parts with higher peak pulse current ratings (5KP series at 40.5A, 15KPA series at 119.7A) provide enhanced transient suppression capability. These higher ratings do not affect circuit compatibility; they represent improved performance margins for transient events. Selection depends on application transient severity requirements.

Q: Are the Vishay 5KP78AHE3 variants suitable for non-automotive applications?

A: Yes. The AEC-Q101 automotive qualification of the 5KP78AHE3/54 and 5KP78AHE3/73 indicates enhanced reliability screening and quality assurance. These parts are suitable for any application requiring high reliability, not exclusively automotive use.

Q: What packaging differences exist among the substitute options?

A: Packaging differences are limited to distribution format: Bulk (standard), Tape & Reel (TR) for automated assembly, and Cut Tape (CT) for semi-automated handling. All variants use identical P600 axial through-hole component geometry. Packaging selection depends on assembly process requirements, not electrical performance.

Q: Does the lower clamping voltage of substitute parts (126V vs. 132.3V) affect circuit protection?

A: No. The clamping voltage difference falls within the normal manufacturing tolerance band for this voltage class. All parts maintain the same 78V reverse standoff voltage, which determines circuit protection threshold. The slightly lower clamping voltage in substitutes represents tighter manufacturing control and does not compromise protection effectiveness.

Q: Which substitute part should be selected for new designs?

A: For new designs, select from active product status parts based on application requirements: 5KP78A-B for standard industrial use, 15KPA78AE3/TR13 for enhanced transient protection, or 5KP78AHE3 variants for automotive and high-reliability applications. All are functionally equivalent to the obsolete 3KP78-B.