SMDJ78C Equivalent & Substitute Parts

Part Overview

The SMDJ78C is a bidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This part operates with a 78V reverse standoff voltage and provides 3000W peak pulse power dissipation in a DO-214AB (SMC) package. The SMDJ78C is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Key Parameters

Parameter	Value
Manufacturer Part Number	SMDJ78C
Manufacturer	Littelfuse Inc.
Category	Transient Voltage Suppressors (TVS)
Type	Zener
Bidirectional Channels	1
Voltage - Reverse Standoff (Typ)	78V
Voltage - Breakdown (Min)	82.13V
Voltage - Clamping (Max) @ Ipp	132.3V
Current - Peak Pulse (10/1000µs)	23.8A
Power - Peak Pulse	3000W
Operating Temperature	-65°C ~ 150°C (TJ)
Mounting Type	Surface Mount
Package / Case	DO-214AB, SMC
RoHS Status	ROHS3 Compliant
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the SMDJ78C is determined by strict alignment of the following electrical and mechanical parameters:

Critical Parameters for Substitution:

Voltage - Reverse Standoff (Typ): 78V
Package / Case: DO-214AB, SMC
Mounting Type: Surface Mount
Bidirectional Channels: 1
Type: Zener

Acceptable Variation Ranges:

Voltage - Breakdown (Min): 82.13V to 86.7V
Voltage - Clamping (Max) @ Ipp: 126V to 132.3V
Current - Peak Pulse (10/1000µs): 11.4A to 23.9A
Power - Peak Pulse: 1500W to 3000W
Operating Temperature: -65°C to -50°C (minimum), 150°C to 175°C (maximum)

Substitute parts are grouped into two categories based on power dissipation capability: 3000W devices (full equivalents) and 1500W devices (reduced-power alternatives). All substitute parts maintain the 78V standoff voltage and DO-214AB package specification required for direct replacement.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (Typ)	Voltage - Breakdown (Min)	Voltage - Clamping (Max) @ Ipp	Current - Peak Pulse (10/1000µs)	Power - Peak Pulse	Operating Temperature	Product Status
SMDJ78C	Littelfuse Inc.	78V	82.13V	132.3V	23.8A	3000W	-65°C ~ 150°C	Obsolete
SMDJ78CA	Alpha & Omega Semiconductor Inc.	78V	86.7V	126V	23.9A	3000W	-55°C ~ 150°C	Active
SMC3K78CA-M3/9A	Vishay General Semiconductor - Diodes Division	78V	86.7V	126V	23.8A	3000W	-55°C ~ 150°C	Active
SMC3K78CAHM3/57	Vishay General Semiconductor - Diodes Division	78V	86.7V	126V	23.8A	3000W	-55°C ~ 150°C	Active
SMCJ78CA	MDD	78V	86.7V	126V	11.9A	1500W	-50°C ~ 150°C	Active
SMCJ78CA-TP	Micro Commercial Co	78V	86.7V	126V	11.9A	1500W	-55°C ~ 175°C	Active
SMCJ78CAE3/TR13	Microchip Technology	78V	86.7V	126V	11.4A	1500W	-65°C ~ 150°C	Active
SMLJ78CA	Bourns Inc.	78V	86.7V	126V	22.8A	3000W	-55°C ~ 150°C	Active
SMLJ78CA-TP	Micro Commercial Co	78V	86.7V	126V	22.8A	3000W	-55°C ~ 175°C	Active

Engineering Selection Recommendations

Full-Power Equivalents (3000W): SMDJ78CA, SMC3K78CA-M3/9A, SMC3K78CAHM3/57, SMLJ78CA, and SMLJ78CA-TP are direct functional equivalents to the SMDJ78C. These parts maintain identical power dissipation and peak pulse current specifications. All are active products with ROHS3 compliance. SMC3K78CAHM3/57 carries AEC-Q101 automotive qualification, suitable for applications requiring automotive-grade reliability.

Reduced-Power Alternatives (1500W): SMCJ78CA, SMCJ78CA-TP, and SMCJ78CAE3/TR13 operate at half the power dissipation (1500W) with proportionally reduced peak pulse current (11.4A to 11.9A). These parts are suitable only for applications where transient energy levels do not exceed 1500W. SMCJ78CAE3/TR13 maintains the original -65°C minimum operating temperature of the SMDJ78C.

Compliance Considerations: All substitute parts are ROHS3 compliant. SMLJ78CA carries REACH Affected status; all others are REACH Unaffected or Unaffected. Selection should account for supply chain compliance requirements specific to the end application.

Frequently Asked Questions (FAQ)

Q: Can I use a 1500W substitute part in place of the SMDJ78C? A: Only if your circuit's transient energy does not exceed 1500W. The SMDJ78C is rated for 3000W peak pulse power. Using a lower-power device in a higher-energy environment will result in device failure.

Q: What is the difference between SMC3K78CA-M3/9A and SMC3K78CAHM3/57? A: Both are Vishay TransZorb® devices with identical electrical specifications (78V standoff, 126V clamp, 23.8A peak pulse, 3000W power). SMC3K78CAHM3/57 carries AEC-Q101 automotive qualification; SMC3K78CA-M3/9A does not. Select based on automotive requirement.

Q: Are all substitute parts available in the same DO-214AB package? A: Yes. All listed substitute parts use DO-214AB (SMC) packaging, ensuring mechanical and thermal compatibility with the original SMDJ78C footprint.

Q: Does operating temperature range affect substitution? A: Operating temperature range is a secondary consideration. The SMDJ78C operates -65°C to 150°C. Most substitutes operate -55°C to 150°C. If your application requires -65°C minimum operation, select SMCJ78CAE3/TR13 or verify that -55°C minimum is acceptable for your design.

Q: What does "Bidirectional Channels: 1" mean? A: This indicates a single bidirectional TVS diode that protects against both positive and negative transient overvoltages on a single signal line. All substitute parts maintain this specification.

Q: Can I substitute based on clamping voltage alone? A: No. Clamping voltage must be evaluated alongside peak pulse current and power dissipation. The SMDJ78C clamps at 132.3V with 23.8A; most substitutes clamp at 126V with 23.8A to 23.9A. This 6.3V difference is within acceptable tolerance for general-purpose protection but should be verified against your circuit's overvoltage threshold requirements.

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