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SMBJ78 Equivalent & Substitute Parts
Part Overview
The SMBJ78 is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. The device features a 78V reverse standoff voltage with a 132.3V maximum clamping voltage and 4.8A peak pulse current capability in a DO-214AA (SMB) package. The SMBJ78 is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Voltage - Reverse Standoff (Typ) | 78V |
| Voltage - Breakdown (Min) | 82.13V |
| Voltage - Clamping (Max) @ Ipp | 132.3V |
| Current - Peak Pulse (10/1000µs) | 4.8A |
| Power - Peak Pulse | 600W |
| Unidirectional Channels | 1 |
| Package / Case | DO-214AA, SMB |
| Mounting Type | Surface Mount |
| RoHS Status | ROHS3 Compliant |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
Substitute Part Grouping Explanation
Substitution of the SMBJ78 is determined by the following critical parameters:
- Voltage - Reverse Standoff (Typ): 78V (all substitutes maintain this specification)
- Voltage - Clamping (Max) @ Ipp: Must not exceed 132.3V to ensure equivalent protection performance
- Current - Peak Pulse (10/1000µs): Minimum 4.7A required; 4.8A preferred for full equivalence
- Power - Peak Pulse: 600W (maintained across all substitutes)
- Package / Case: DO-214AA, SMB (surface-mount compatibility required)
- Unidirectional Channels: 1 (single-channel configuration)
- RoHS Status: ROHS3 Compliant (regulatory requirement)
All identified substitute parts meet these core substitution criteria and are classified as active products, providing long-term availability advantages over the obsolete SMBJ78.
Parameter Comparison
| Parameter | SMBJ78 (Littelfuse) | SMBJ78A (MDD) | SMBJ78A-13-F (Diodes Inc.) | SMBJ78A-TP (Micro Commercial) |
|---|---|---|---|---|
| Voltage - Reverse Standoff (Typ) | 78V | 78V | 78V | 78V |
| Voltage - Breakdown (Min) | 82.13V | 86.7V | 86.7V | 86.7V |
| Voltage - Clamping (Max) @ Ipp | 132.3V | 126V | 126V | 126V |
| Current - Peak Pulse (10/1000µs) | 4.8A | 4.8A | 4.7A | 4.7A |
| Power - Peak Pulse | 600W | 600W | 600W | 600W |
| Unidirectional Channels | 1 | 1 | 1 | 1 |
| Package / Case | DO-214AA, SMB | DO-214AA, SMB | DO-214AA, SMB | DO-214AA, SMB |
| Mounting Type | Surface Mount | Surface Mount | Surface Mount | Surface Mount |
| Operating Temperature | -65°C ~ 150°C | -50°C ~ 150°C | -55°C ~ 150°C | -55°C ~ 175°C |
| RoHS Status | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant |
| Product Status | Obsolete | Active | Active | Active |
Engineering Selection Recommendations
All three substitute parts (SMBJ78A from MDD, SMBJ78A-13-F from Diodes Incorporated, and SMBJ78A-TP from Micro Commercial Co) are classified as active products with ROHS3 compliance and REACH unaffected status, ensuring regulatory compliance and long-term supply availability.
The SMBJ78A (MDD) and SMBJ78A-TP (Micro Commercial Co) both maintain the 4.8A peak pulse current specification matching the original SMBJ78. The SMBJ78A-13-F (Diodes Incorporated) operates at 4.7A, representing a 1.9% reduction in peak pulse current capability.
All substitutes feature a maximum clamping voltage of 126V, which is 4.3V lower than the original SMBJ78 specification of 132.3V. This represents improved clamping performance and tighter voltage regulation.
The SMBJ78A-TP (Micro Commercial Co) offers the widest operating temperature range (-55°C ~ 175°C), extending 25°C above the standard upper limit. The SMBJ78A (MDD) operates within a narrower temperature range (-50°C ~ 150°C) compared to the original specification.
Frequently Asked Questions (FAQ)
Q: Can SMBJ78A parts directly replace the obsolete SMBJ78?
A: Yes. All substitute parts maintain the critical 78V reverse standoff voltage, 600W peak pulse power, single-channel unidirectional configuration, and DO-214AA (SMB) surface-mount package. The lower clamping voltage (126V vs. 132.3V) represents improved performance rather than a limitation.
Q: What is the difference between SMBJ78A from different manufacturers?
A: All three manufacturers (MDD, Diodes Incorporated, and Micro Commercial Co) produce SMBJ78A variants meeting the same core electrical specifications. The primary differences are peak pulse current (4.8A vs. 4.7A) and operating temperature ranges. Selection depends on supply availability and specific thermal requirements.
Q: Are there package compatibility concerns?
A: No. All substitute parts use the DO-214AA (SMB) surface-mount package, ensuring direct PCB footprint compatibility with the original SMBJ78 design.
Q: Does the lower clamping voltage (126V vs. 132.3V) affect circuit protection?
A: No. The lower clamping voltage indicates tighter voltage regulation and improved transient suppression performance. This is a beneficial characteristic for overvoltage protection applications.
Q: What compliance certifications apply to these substitutes?
A: All substitute parts are ROHS3 compliant and REACH unaffected, meeting current regulatory requirements for electronic component manufacturing and use.
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