SMLJ78A Equivalent & Substitute Parts

Part Overview

The SMLJ78A is a unidirectional transient voltage suppressor (TVS) diode manufactured by Bourns Inc., designed for general-purpose overvoltage protection in surface-mount applications. This component features a 78V reverse standoff voltage, 126V maximum clamping voltage, and 3000W peak pulse power rating in a DO-214AB (SMC) package. The part is active in production status and ROHS3 compliant. Equivalent and substitute parts are identified to support procurement flexibility, inventory management, and design continuity across multiple manufacturers while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value	Unit
Manufacturer Part Number	SMLJ78A	—
Manufacturer	Bourns Inc.	—
Category	Transient Voltage Suppressors (TVS)	—
Type	Zener	—
Unidirectional Channels	1	—
Voltage - Reverse Standoff (Typ)	78	V
Voltage - Breakdown (Min)	86.7	V
Voltage - Clamping (Max) @ Ipp	126	V
Current - Peak Pulse (10/1000µs)	22.8	A
Power - Peak Pulse	3000	W
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	DO-214AB, SMC	—
RoHS Status	ROHS3 Compliant	—
Product Status	Active	—

Substitute Part Grouping Explanation

Substitute parts for the SMLJ78A are classified based on strict electrical and mechanical parameter alignment. The primary substitution criteria are:

Critical Parameters for Substitution:

Voltage - Reverse Standoff (Typ): 78V
Voltage - Clamping (Max) @ Ipp: 126V
Voltage - Breakdown (Min): 86.7V
Unidirectional Channels: 1
Package / Case: DO-214AB, SMC
Mounting Type: Surface Mount
Type: Zener

Substitute Categories:

Direct Equivalents maintain all critical electrical parameters and identical power ratings (3000W):

SMDJ78A (Alpha & Omega Semiconductor Inc.)

Functional Equivalents maintain all critical voltage parameters with identical package and mounting but differ in peak pulse current and power rating:

SMCJ78A (MDD)
SMCJ78A-TP (Micro Commercial Co)
TPSMC91A (Littelfuse Inc.)

Enhanced Performance Equivalents maintain all critical voltage parameters with identical package and mounting but provide higher peak pulse current and power ratings (5000W):

5.0SMDJ78A (Taiwan Semiconductor Corporation)
5.0SMDJ78A-T7 (Littelfuse Inc.)

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Breakdown Min (V)	Voltage - Clamping Max (V)	Current - Peak Pulse (A)	Power - Peak Pulse (W)	Operating Temp (°C)	Package	RoHS Status	Product Status
SMLJ78A	Bourns Inc.	78	86.7	126	22.8	3000	-55 to 150	DO-214AB, SMC	ROHS3 Compliant	Active
SMDJ78A	Alpha & Omega Semiconductor Inc.	78	86.7	126	23.9	3000	-55 to 150	DO-214AB, SMC	ROHS3 Compliant	Active
5.0SMDJ78A	Taiwan Semiconductor Corporation	78	86.7	126	39.7	5000	-55 to 175	DO-214AB, SMC	ROHS3 Compliant	Active
5.0SMDJ78A-T7	Littelfuse Inc.	78	86.7	126	39.7	5000	-65 to 150	DO-214AB, SMC	ROHS3 Compliant	Active
SMCJ78A	MDD	78	86.7	126	11.9	1500	-50 to 150	DO-214AB, SMC	ROHS3 Compliant	Active
SMCJ78A-TP	Micro Commercial Co	78	86.7	126	11.9	1500	-55 to 175	DO-214AB, SMC	ROHS3 Compliant	Active
TPSMC91A	Littelfuse Inc.	77.8	86.5	125	12.2	1500	-55 to 150	DO-214AB, SMC	ROHS3 Compliant	Active

Engineering Selection Recommendations

Direct Substitution (SMDJ78A): SMDJ78A from Alpha & Omega Semiconductor Inc. is the closest direct equivalent, matching all critical voltage parameters, power rating, and operating temperature range. This part maintains identical electrical performance with marginally higher peak pulse current (23.9A vs 22.8A). ROHS3 compliance and active product status confirm suitability for new designs and production continuity.

Enhanced Performance Substitution (5.0SMDJ78A, 5.0SMDJ78A-T7): Both 5.0SMDJ78A and 5.0SMDJ78A-T7 maintain identical voltage specifications while providing higher peak pulse current (39.7A) and power rating (5000W). These parts are suitable for applications requiring greater transient energy absorption. 5.0SMDJ78A-T7 from Littelfuse Inc. includes automotive-grade qualification (AEC-Q101) and extended lower temperature range (-65°C), appropriate for automotive and harsh environment applications.

Reduced Power Substitution (SMCJ78A, SMCJ78A-TP, TPSMC91A): SMCJ78A, SMCJ78A-TP, and TPSMC91A provide lower peak pulse current (11.9A to 12.2A) and power rating (1500W). These parts maintain voltage specifications within acceptable tolerance and are suitable for applications with lower transient energy requirements. TPSMC91A includes automotive-grade qualification (AEC-Q101) from Littelfuse Inc. SMCJ78A-TP offers extended upper temperature range (-55°C to 175°C).

Compliance and Status: All substitute parts maintain ROHS3 compliance and active production status, ensuring regulatory alignment and long-term availability.

Frequently Asked Questions (FAQ)

Q: Can SMDJ78A directly replace SMLJ78A without circuit modification? A: Yes. SMDJ78A maintains identical voltage specifications (78V reverse standoff, 126V clamping), identical power rating (3000W), and identical package (DO-214AB, SMC). The marginal increase in peak pulse current (23.9A vs 22.8A) represents improved performance with no negative impact on circuit operation.

Q: What is the difference between direct equivalents and enhanced performance equivalents? A: Direct equivalents (SMDJ78A) match the SMLJ78A in all electrical parameters including power rating. Enhanced performance equivalents (5.0SMDJ78A, 5.0SMDJ78A-T7) maintain identical voltage specifications but provide higher peak pulse current (39.7A) and power rating (5000W), suitable for applications with greater transient stress.

Q: Can reduced power parts (SMCJ78A, SMCJ78A-TP, TPSMC91A) replace SMLJ78A? A: Reduced power parts maintain voltage specifications but provide lower peak pulse current (11.9A to 12.2A) and power rating (1500W). Substitution is valid only if the application's transient energy requirement does not exceed 1500W. Circuit analysis is required to confirm suitability.

Q: Are all substitute parts available in the same package? A: Yes. All substitute parts use DO-214AB (SMC) surface-mount package, ensuring mechanical and footprint compatibility on PCBs designed for SMLJ78A.

Q: Which substitute part is recommended for automotive applications? A: 5.0SMDJ78A-T7 from Littelfuse Inc. and TPSMC91A from Littelfuse Inc. both carry automotive-grade qualification (AEC-Q101). 5.0SMDJ78A-T7 provides enhanced power rating (5000W) and extended lower temperature range (-65°C), suitable for demanding automotive environments.

Q: Do all substitute parts comply with ROHS3? A: Yes. All substitute parts listed maintain ROHS3 compliance, ensuring regulatory alignment with current environmental standards.

Q: What is the operating temperature consideration when selecting substitutes? A: SMLJ78A operates from -55°C to 150°C. Substitute parts offer varying ranges: SMCJ78A-TP and 5.0SMDJ78A extend to 175°C upper limit; 5.0SMDJ78A-T7 extends to -65°C lower limit. Selection depends on application temperature requirements.

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