SA78CA Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA78CA is a 78V Zener transient voltage suppressor diode manufactured by onsemi in DO-15 through-hole packaging. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. The SA78CA provides 126V maximum clamping voltage at 4A peak pulse current, suitable for general-purpose transient voltage suppression applications.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	78V
Voltage - Breakdown (Min)	86.7V
Voltage - Clamping (Max) @ Ipp	126V
Current - Peak Pulse (10/1000µs)	4A
Power - Peak Pulse	500W
Type	Zener
Bidirectional Channels	1
Mounting Type	Through Hole
Package / Case	DO-204AC, DO-15, Axial
Applications	General Purpose

Substitute Part Grouping Explanation

Substitute parts for the SA78CA are classified into two categories based on electrical and mechanical compatibility:

Direct Equivalents (Identical Electrical Performance): Parts maintaining the same reverse standoff voltage (78V), breakdown voltage (86.7V minimum), clamping voltage (126V maximum), and peak pulse current (4A nominal) with identical or compatible packaging. These parts are functionally interchangeable in the same circuit application.

Similar Substitutes (Comparable Electrical Performance with Package Variation): Parts with matching voltage specifications but different mounting technology (surface mount versus through-hole) or slightly elevated performance parameters. These require circuit board redesign or layout modification.

Key Parameters Determining Substitution:

Voltage - Reverse Standoff: 78V (±tolerance)
Voltage - Clamping (Max) @ Ipp: 126V (maximum allowable)
Current - Peak Pulse: 4A minimum
Bidirectional Channels: 1
Type: Zener
Applications: General Purpose

Parameter Comparison

Part Number	Manufacturer	Standoff Voltage	Breakdown (Min)	Clamping (Max)	Peak Pulse Current	Power - Peak Pulse	Package Type	Product Status
SA78CA	onsemi	78V	86.7V	126V	4A	500W	DO-15	Obsolete
SA78CA	Taiwan Semiconductor Corporation	78V	86.7V	126V	4.1A	500W	DO-204AC (DO-15)	Active
SA78CA-E3/54	Vishay General Semiconductor - Diodes Division	78V	86.7V	126V	4A	500W	DO-204AC (DO-15)	Active
SA78CAHE3/54	Vishay General Semiconductor - Diodes Division	78V	86.7V	126V	4A	500W	DO-204AC (DO-15)	Active
SA78CA-AP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
SA78CA-BP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
SA78CA-TP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
P5KE78CA-AP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
P5KE78CA-BP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
P5KE78CA-TP	Micro Commercial Co	78V	86.7V	126V	4A	500W	DO-15	Active
SMBJ85CA-TR	STMicroelectronics	85V	94V	137V	4.6A	600W	SMB	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Replacement):

SA78CA-E3/54 and SA78CAHE3/54 from Vishay General Semiconductor are active products with identical electrical specifications and DO-204AC (DO-15) packaging. The SA78CAHE3/54 variant includes AEC-Q101 automotive qualification, suitable for applications requiring automotive-grade components.

SA78CA variants from Taiwan Semiconductor Corporation and Micro Commercial Co (SA78CA-AP, SA78CA-BP, SA78CA-TP) maintain identical voltage specifications and through-hole packaging. These parts are in active production status with ROHS3 compliance.

Secondary Substitutes (Performance-Compatible):

P5KE78CA series from Micro Commercial Co (P5KE78CA-AP, P5KE78CA-BP, P5KE78CA-TP) provide identical electrical performance with extended operating temperature range (-65°C to 175°C versus -55°C to 175°C). These parts are suitable where wider temperature operation is required.

Alternative with Package Modification:

SMBJ85CA-TR from STMicroelectronics operates at 85V standoff with 137V clamping voltage and 4.6A peak pulse current. This surface-mount SMB package alternative requires circuit board redesign and is suitable only when surface-mount technology is preferred and the slightly elevated voltage specifications are acceptable for the application.

Frequently Asked Questions (FAQ)

Q: Can SA78CA-E3/54 directly replace the obsolete onsemi SA78CA?

A: Yes. Both parts maintain 78V reverse standoff voltage, 126V maximum clamping voltage, and 4A peak pulse current. The DO-204AC (DO-15) package is mechanically and electrically compatible with the original DO-15 package. No circuit modifications are required.

Q: What is the difference between SA78CA variants from different manufacturers?

A: All SA78CA variants (Taiwan Semiconductor Corporation, Vishay, Micro Commercial Co) meet the same electrical specifications for the 78V/126V clamping rating. Differences exist in product status (active versus obsolete), compliance certifications (ROHS3), and operating temperature ranges. Selection depends on supply chain availability and compliance requirements.

Q: Is SMBJ85CA-TR a suitable replacement?

A: SMBJ85CA-TR is electrically comparable but not a direct replacement. The 85V standoff voltage and 137V clamping voltage are elevated compared to the 78V/126V specification. Additionally, the SMB surface-mount package requires circuit board redesign. Use only when higher voltage ratings are acceptable and surface-mount technology is preferred.

Q: What does the suffix designation mean (AP, BP, TP)?

A: Suffix designations indicate packaging and tape configuration variants from Micro Commercial Co. All three variants (AP, BP, TP) maintain identical electrical specifications and are functionally interchangeable. Selection is based on supply chain availability and packaging preference.

Q: Are Vishay SA78CA-E3/54 and SA78CAHE3/54 interchangeable?

A: Both parts are electrically identical with identical DO-204AC (DO-15) packaging. SA78CAHE3/54 includes AEC-Q101 automotive qualification. Use SA78CAHE3/54 in applications requiring automotive-grade certification; otherwise, both parts are interchangeable.

Q: What compliance standards apply to these substitute parts?

A: Active substitute parts comply with ROHS3 and maintain REACH Unaffected status. SA78CAHE3/54 includes AEC-Q101 automotive qualification. All parts are classified under ECCN EAR99 and HTSUS 8541.10.0080.

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