SA78 Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA78 is a unidirectional Zener-type transient voltage suppressor diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection applications. The device features a 78V reverse standoff voltage with a 132.3V maximum clamping voltage at peak pulse current, housed in a DO-204AC (DO-15) axial through-hole package. The SA78 is classified as obsolete, making identification of active equivalent parts essential for new designs and ongoing production support.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	78	V
Voltage - Breakdown (Min)	82.13	V
Voltage - Clamping (Max) @ Ipp	132.3	V
Current - Peak Pulse (10/1000µs)	4	A
Power - Peak Pulse	500	W
Operating Temperature Range	-55 to 175	°C (TJ)
Mounting Type	Through Hole	-
Package / Case	DO-204AC, DO-15, Axial	-
Type	Zener	-
Unidirectional Channels	1	-

Substitute Part Grouping Explanation

Substitution of the SA78 is determined by strict equivalence across the following critical parameters:

Voltage - Reverse Standoff (Typ): 78V
Voltage - Clamping (Max) @ Ipp: Must not exceed 132.3V
Current - Peak Pulse (10/1000µs): Minimum 4A
Power - Peak Pulse: 500W
Mounting Type: Through Hole
Package / Case: DO-204AC, DO-15, Axial
Type: Zener
Unidirectional Channels: 1
Operating Temperature Range: -55°C to 175°C minimum

All substitute parts listed maintain these electrical and mechanical specifications within the defined tolerances, ensuring functional compatibility in existing circuit designs.

Parameter Comparison

Parameter	SA78 (Littelfuse)	SA78A (Taiwan Semiconductor)	P5KE78A-TP (Micro Commercial)	SA78A-AP (Micro Commercial)	SA78A-BP (Micro Commercial)	SA78A-TP (Micro Commercial)
Voltage - Reverse Standoff (Typ)	78V	78V	78V	78V	78V	78V
Voltage - Breakdown (Min)	82.13V	86.7V	86.7V	86.7V	86.7V	86.7V
Voltage - Clamping (Max) @ Ipp	132.3V	126V	126V	126V	126V	126V
Current - Peak Pulse (10/1000µs)	4A	4.1A	4A	4A	4A	4A
Power - Peak Pulse	500W	500W	500W	500W	500W	500W
Operating Temperature Range	-55 to 175°C	-55 to 175°C	-65 to 175°C	-55 to 175°C	-55 to 175°C	-55 to 175°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	DO-204AC, DO-15	DO-204AC, DO-15	DO-15	DO-15	DO-15	DO-15
Type	Zener	Zener	Zener	Zener	Zener	Zener
Unidirectional Channels	1	1	1	1	1	1
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified	Not specified	Not specified	Not specified
Product Status	Obsolete	Active	Active	Active	Active	Active

Engineering Selection Recommendations

The SA78 is obsolete and no longer in active production. All listed substitute parts are active components with current manufacturing support.

SA78A (Taiwan Semiconductor Corporation) provides direct functional equivalence with improved clamping voltage performance (126V vs. 132.3V) and maintains identical reverse standoff voltage and operating temperature specifications. This part is available in tape and reel packaging.

P5KE78A-TP, SA78A-AP, SA78A-BP, and SA78A-TP (all Micro Commercial Co) offer equivalent electrical performance with active product status. These variants differ primarily in packaging format (bulk) and minor temperature range extensions in the case of P5KE78A-TP (-65°C lower limit). All maintain the critical 78V reverse standoff voltage and 500W peak pulse power rating.

All substitute parts maintain ROHS3 compliance and REACH unaffected status, ensuring regulatory compatibility with modern manufacturing and environmental standards.

Frequently Asked Questions (FAQ)

Q: Can SA78A variants from different manufacturers be used interchangeably?

A: Yes. SA78A-AP, SA78A-BP, and SA78A-TP from Micro Commercial Co are functionally equivalent to SA78A from Taiwan Semiconductor Corporation. All maintain identical electrical specifications: 78V reverse standoff voltage, 126V maximum clamping voltage, 4A peak pulse current, and 500W peak pulse power. Differences are limited to packaging format (bulk vs. tape and reel) and inventory availability.

Q: What is the difference between P5KE78A-TP and SA78A variants?

A: P5KE78A-TP differs from SA78A variants in extended lower operating temperature limit (-65°C vs. -55°C). Electrical specifications are equivalent: 78V reverse standoff, 126V clamping voltage, 4A peak pulse current, and 500W peak pulse power. Both are suitable for general-purpose transient voltage suppression applications.

Q: Is the clamping voltage difference between SA78 (132.3V) and SA78A (126V) significant?

A: The SA78A clamping voltage of 126V is lower than the original SA78 specification of 132.3V. This represents improved clamping performance and is within acceptable substitution parameters for general-purpose applications. Circuit designers must verify that the lower clamping voltage meets specific application requirements.

Q: Are all substitute parts available in DO-204AC (DO-15) axial through-hole packaging?

A: SA78A from Taiwan Semiconductor Corporation is available in DO-204AC (DO-15) axial packaging. Micro Commercial Co variants (P5KE78A-TP, SA78A-AP, SA78A-BP, SA78A-TP) are specified in DO-15 axial packaging. Both designations refer to the same physical form factor and are mechanically compatible.

Q: What compliance certifications apply to these substitute parts?

A: SA78A (Taiwan Semiconductor) is ROHS3 compliant. All substitute parts maintain REACH unaffected status. Specific RoHS compliance for Micro Commercial Co variants is not specified in available documentation but should be confirmed with the supplier for regulatory compliance verification.

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