SA78A Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA78A is a unidirectional Zener-type transient voltage suppressor diode manufactured by onsemi, designed for general-purpose overvoltage protection applications. Specified with a 78V reverse standoff voltage and 126V maximum clamping voltage at peak pulse current, the SA78A operates in the DO-15 (DO-204AC) axial through-hole package. The main part is classified as obsolete, necessitating identification of active equivalent and substitute components that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

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

Substitute Part Grouping Explanation

Substitution of the SA78A is determined by strict equivalence across the following electrical and mechanical parameters:

Voltage - Reverse Standoff (Typ): 78V
Voltage - Breakdown (Min): 86.7V
Voltage - Clamping (Max) @ Ipp: 126V
Current - Peak Pulse (10/1000µs): 4A (or 4.1A within tolerance)
Power - Peak Pulse: 500W
Type: Zener, Unidirectional
Mounting Type: Through Hole
Package / Case: DO-204AC or DO-15 Axial

Substitute parts are classified into two categories:

Direct Manufacturer Equivalents: Parts from Vishay General Semiconductor (SA78A-E3/54, SA78AHE3/54) that maintain identical electrical specifications and are manufactured to the same base product number SA78.

Similar Functional Equivalents: Parts from Micro Commercial Co (P5KE78A series) and Taiwan Semiconductor Corporation (SA78A) that meet all electrical parameters and package requirements but may differ in product status, operating temperature range, or packaging format.

Parameter Comparison

Part Number	Manufacturer	Vwm (Typ) V	Vbr (Min) V	Vc (Max) V	Ipp A	Ppk W	Package	Product Status	Operating Temp °C
SA78A	onsemi	78	86.7	126	4	500	DO-15	Obsolete	—
SA78A-E3/54	Vishay	78	86.7	126	4	500	DO-204AC	Active	-55 to 175
SA78AHE3/54	Vishay	78	86.7	126	4	500	DO-204AC	Active	-55 to 175
P5KE78A-AP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-65 to 175
P5KE78A-BP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-65 to 175
P5KE78A-TP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-65 to 175
SA78A	Taiwan Semiconductor	78	86.7	126	4.1	500	DO-204AC	Active	-55 to 175
SA78A-AP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-55 to 175
SA78A-BP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-55 to 175
SA78A-TP	Micro Commercial Co	78	86.7	126	4	500	DO-15	Active	-55 to 175

Engineering Selection Recommendations

For Active Production: Vishay SA78A-E3/54 and SA78AHE3/54 are direct equivalents with active product status and ROHS3 compliance. SA78AHE3/54 includes AEC-Q101 automotive qualification for applications requiring automotive-grade reliability.

For General-Purpose Applications: Micro Commercial Co P5KE78A series (P5KE78A-AP, P5KE78A-BP, P5KE78A-TP) and SA78A variants (SA78A-AP, SA78A-BP, SA78A-TP) provide active alternatives with identical electrical specifications. These parts support extended operating temperature range (-65°C to 175°C for P5KE series) and are available in bulk packaging.

For Temperature-Constrained Designs: Taiwan Semiconductor SA78A offers active status with -55°C to 175°C operating range and ROHS3 compliance, with peak pulse current of 4.1A within specification tolerance.

All substitute parts maintain compliance with REACH regulations and EAR99 export classification. Selection should be based on product availability, packaging format requirements (tape & reel versus bulk), and operating temperature specifications for the target application.

Frequently Asked Questions (FAQ)

Q: Can SA78A-E3/54 directly replace the obsolete onsemi SA78A?

A: Yes. SA78A-E3/54 maintains identical electrical specifications (78V standoff, 126V clamping, 4A peak pulse current, 500W peak power) and through-hole mounting. The primary difference is package designation (DO-204AC versus DO-15), which are mechanically equivalent. Both are unidirectional Zener TVS diodes for general-purpose overvoltage protection.

Q: What is the difference between Vishay SA78A-E3/54 and SA78AHE3/54?

A: Both parts are electrically and mechanically identical with 78V standoff voltage and 126V clamping voltage. SA78AHE3/54 includes AEC-Q101 automotive qualification and automotive-grade designation, making it suitable for automotive applications requiring enhanced reliability screening and traceability.

Q: Are Micro Commercial Co P5KE78A parts compatible with the original SA78A?

A: Yes. P5KE78A-AP, P5KE78A-BP, and P5KE78A-TP maintain all critical electrical parameters (78V standoff, 86.7V breakdown minimum, 126V clamping, 4A peak pulse current, 500W peak power) and DO-15 through-hole packaging. These parts are available in bulk format and support extended temperature range (-65°C to 175°C).

Q: What packaging formats are available for SA78A substitutes?

A: Vishay parts (SA78A-E3/54, SA78AHE3/54) are supplied in tape & reel format. Micro Commercial Co variants and Taiwan Semiconductor SA78A are available in bulk packaging. All maintain DO-15 or DO-204AC axial through-hole package compatibility.

Q: Do all substitute parts meet RoHS compliance?

A: Vishay SA78A-E3/54 and SA78AHE3/54 are ROHS3 compliant. Taiwan Semiconductor SA78A is ROHS3 compliant. Micro Commercial Co parts do not specify RoHS status in provided data. All parts are REACH unaffected.

Q: Which substitute offers the widest operating temperature range?

A: Micro Commercial Co P5KE78A series (P5KE78A-AP, P5KE78A-BP, P5KE78A-TP) supports -65°C to 175°C operating range, providing 10°C lower minimum temperature compared to Vishay and Taiwan Semiconductor alternatives.

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