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Taiwan Semiconductor Corporation SMBJ78
- Part No.:
- SMBJ78
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SMBJ78.pdf
- Description:
- 600W, 96.4V, 10%, UNIDIRECTIONAL
- Quantity:
- Payment:
- Shipping:
Inventory:7,914
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Product details
Overview
SMBJ78 from Taiwan Semiconductor is a unidirectional 600W surface-mount transient voltage suppressor (TVS) diode in DO-214AA (SMB) package, with 78 V working stand-off voltage (VWM), 86.7–106 V breakdown voltage (VBR), and 139 V maximum clamping voltage (VC) at 4.5 A peak impulse current - designed for automotive load-dump and inductive switching surge protection in power supply rails.
For engineers reviewing the SMBJ78 datasheet, SMBJ78 pinout, SMBJ78 application, or SMBJ78 equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b, junction-to-ambient thermal resistance (55 °C/W), moisture sensitivity level (MSL 1), and unidirectional polarity marking for correct PCB orientation.
Technical Context
The SMBJ78 operates as a unidirectional avalanche diode, triggered when reverse voltage exceeds its specified VBR range (86.7–106 V @ 1 mA). It clamps transients to ≤139 V at 4.5 A (10/1000 µs waveform), limiting energy dissipation to 600 W non-repetitive peak pulse power while maintaining <1 µA leakage above 10 V.
Its glass-passivated junction ensures stable breakdown characteristics and fast response (<1.0 ps), and it meets JESD201 Class 2 whisker resistance and UL 94V-0 flammability requirements - critical for automotive and industrial control module reliability under EFT and load-switching stress.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - maximum continuous reverse operating voltage before conduction begins |
| VBR min / max | 86.7 V / 106 V @ 1 mA - guaranteed avalanche initiation window for predictable turn-on |
| VC @ IPP | 139 V @ 4.5 A (10/1000 µs) - peak clamped voltage protecting downstream ICs from overvoltage damage |
| PPK | 600 W - non-repetitive surge power handling capability per ISO 7637-2 compliance |
| ID @ VWM | <1 µA - minimal leakage current preserves system efficiency and battery life in always-on circuits |
| RθJA | 55 °C/W - thermal resistance defining safe power derating above 25°C ambient |
| Polarity | Cathode band marked - ensures correct unidirectional installation on PCB |
Pinout & Package
DO-214AA (SMB) surface-mount package: 2-terminal, single-die unidirectional TVS diode with cathode band marking on one end; matte tin-plated leads compliant with J-STD-002 solderability and JESD201 Class 2 whisker resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Low-side connection point | Connected to ground or low-impedance return path during clamping event |
| Cathode (banded end) | High-side connection point | Connected to protected line (e.g., 24 V rail); reverse-biased during normal operation |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable, repeatable breakdown voltage across temperature and lifetime |
| Fast response time <1.0 ps | Clamps ESD and EFT transients before sensitive logic or analog circuitry sustains damage |
| ISO 7637-2 Pulse 1/2a/2b/3a/3b compliance | Validated for automotive power-line immunity testing without external filtering |
| MSL Level 1 (per J-STD-020) | Zero floor-life limitation - can be stored indefinitely and mounted without baking |
| RoHS & halogen-free (IEC 61249-2-21) | Meets global environmental compliance for automotive and industrial end-equipment |
Applications
| Automotive Power Rail Protection | Industrial PLC I/O Protection |
|---|---|
Use Scenario: 24 V battery-fed ECUs subjected to load-dump transients up to 120 V per ISO 7637-2 Pulse 5a. IC Role / Device Role / Timing Role: Unidirectional TVS placed between power input and DC-DC converter input stage. Use Value: Clamps surge to ≤139 V within picoseconds, preventing latch-up or permanent damage to buck controller ICs. | Use Scenario: 24 V digital input modules exposed to inductive kickback from solenoid drivers. IC Role / Device Role / Timing Role: TVS connected across input terminal and common rail to shunt flyback energy. Use Value: Limits voltage overshoot to safe levels for optocoupler input stages and microcontroller GPIO protection. |
| LED Driver Overvoltage Clamp | Medical Equipment Power Entry |
Use Scenario: Constant-current LED driver board powered from 48 V supply, vulnerable to field wiring surges. IC Role / Device Role / Timing Role: SMBJ78 placed at DC input connector to clamp transients before bulk capacitor and controller. Use Value: Prevents overvoltage failure of MOSFET gate drivers and current-sense amplifiers during cable disconnect events. | Use Scenario: External 24 V adapter input to diagnostic imaging subsystem requiring high-reliability surge immunity. IC Role / Device Role / Timing Role: Primary-level TVS on main power entry board upstream of EMI filter and fuse. Use Value: Provides first-stage clamping with MSL 1 handling and UL 94V-0 compound for safety-critical enclosure integration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Littelfuse SMAJ78A | Same DO-214AC (SMA) package; 139 V VC @ 4.5 A but 400 W PPK rating | Lower peak power handling limits use in high-energy load-dump scenarios | Select only if layout constraints require smaller SMA footprint and surge energy is limited to ≤400 W |
| ON Semiconductor SMCJ78A | DO-214AB (SMC) package; same 78 V VWM and 139 V VC, but 1500 W PPK rating | Higher surge capacity suits heavy-duty industrial motor drives | Prefer when system-level surge testing exceeds 600 W or requires extended pulse duration margin |
Compared with SMBJ78, SMAJ78A offers smaller size but reduced surge robustness, while SMCJ78A delivers higher power handling in a larger package - choice depends on PCB space, thermal budget, and worst-case transient energy profile.
Availability
SMBJ78 is available at Aetrix Electronics and suitable for automotive body control modules, industrial programmable logic controllers, LED lighting drivers, and medical power entry systems requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for SMBJ78 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Taiwan Semiconductor Corporation (TSC) is a vertically integrated analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in TVS diodes, rectifiers, and power MOSFETs for industrial and automotive markets.
The SMBJ series was developed specifically for high-reliability surface-mount surge protection in harsh environments - emphasizing low clamping ratio, MSL 1 handling, and ISO 7637-2 compliance for automotive electronics and factory automation.
FAQ
What is the maximum clamping voltage of SMBJ78 under standard test conditions?
The SMBJ78 has a maximum clamping voltage (VC) of 139 V when subjected to a 10/1000 µs surge waveform at 4.5 A peak impulse current. This value is measured per ANSI/IEEE C62.35 and defines the upper voltage limit imposed on protected circuitry during transient events - critical for ensuring downstream ICs remain within absolute maximum ratings.
Is SMBJ78 unidirectional or bidirectional, and how is polarity identified?
SMBJ78 is a unidirectional TVS diode, indicated by its part number suffix (no "C" or "CA") and cathode band marking on the DO-214AA package. The banded end is the cathode and must be connected to the protected line (e.g., 24 V rail), while the anode connects to ground - reverse polarity would prevent proper clamping during overvoltage events.
Does SMBJ78 meet automotive surge immunity standards?
Yes, SMBJ78 meets ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b requirements for electrical disturbances in road vehicles. Its 600 W peak pulse power rating, fast response time (<1.0 ps), and controlled clamping behavior enable direct integration into automotive power distribution networks without additional filtering components.
What is the junction-to-ambient thermal resistance (RθJA) of SMBJ78, and why does it matter?
The SMBJ78 has a junction-to-ambient thermal resistance (RθJA) of 55 °C/W. This parameter determines how much the junction temperature rises above ambient per watt of dissipated surge energy - essential for derating calculations in high-temperature environments (e.g., engine compartments) where sustained power dissipation could exceed safe operating limits without adequate PCB copper area.
Can SMBJ78 be used in place of SMBJ78A, and what is the key difference?
No - SMBJ78 and SMBJ78A are not interchangeable without design review. SMBJ78A has tighter VBR tolerance (86.7–95.8 V vs. 86.7–106 V), lower clamping voltage (126 V vs. 139 V), and higher IPP (5.0 A vs. 4.5 A). Substituting SMBJ78 for SMBJ78A may result in earlier conduction and higher clamping during marginal transients, potentially affecting system-level immunity margins.
SMBJ78 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AA, SMB
- Series:
- SMBJ
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 78V
- Voltage - Breakdown (Min):
- 86.7V
- Voltage - Clamping (Max) @ Ipp:
- 139V
- Current - Peak Pulse (10/1000µs):
- 4.5A
- Power - Peak Pulse:
- 600W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AA (SMB)
SMBJ78 FAQ
1.How can I place an order for SMBJ78 through Aetrix?
Please submit a Request for Quotation (RFQ) for SMBJ78 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SMBJ78 reliable?
The price and inventory of SMBJ78 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMBJ78 is usually 5 days.
3.What payment methods are accepted for SMBJ78?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMBJ78 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMBJ78?
SMBJ78 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMBJ78 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SMBJ78?
For technical support, including SMBJ78 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMBJ78 requirements.
6.How does Aetrix verify that SMBJ78 is sourced from the original manufacturer or authorized distributors?
All SMBJ78 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SMBJ78 meets industry standards.
7.What is the process for return or replacement of SMBJ78?
All SMBJ78 units undergo pre-shipment inspection (PSI). If there is an issue with SMBJ78, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SMBJ78 part is unused and in its original packaging.
Return procedure for SMBJ78:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMBJ78 Tags
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