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Vishay General Semiconductor - Diodes Division SMCJ78A-E3/9AT
- Part No.:
- SMCJ78A-E3/9AT
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SMCJ78A-E3/9AT.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AB
- Quantity:
- Payment:
- Shipping:
Inventory:2,347
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Product details
Overview
SMCJ78A-E3/9AT from Vishay General Semiconductor is a unidirectional transient voltage suppressor (TVS) diode in SMC (DO-214AB) package, designed for robust overvoltage protection of DC power rails and signal lines. It features a 78 V stand-off voltage (VWM), 86.7–95.8 V breakdown voltage (VBR) at 1 mA, 1500 W peak pulse power (10/1000 µs), 126 V clamping voltage (VC) at 11.9 A peak surge current, and operates across -55 °C to +150 °C junction temperature - deployed in automotive power supply input stages.
For engineers reviewing the SMCJ78A-E3/9AT datasheet, SMCJ78A-E3/9AT pinout, SMCJ78A-E3/9AT application, or SMCJ78A-E3/9AT equivalent, key selection criteria include clamping performance under 10/1000 µs transients, thermal resistance (RθJA = 75 °C/W), unidirectional polarity marking, RoHS-compliant matte tin plating, and compatibility with automated SMT placement on 8.0 mm × 8.0 mm copper pads.
Technical Context
The SMCJ78A-E3/9AT implements a glass-passivated silicon avalanche junction optimized for fast response (<1 ps) to ESD and lightning-induced surges. Its low incremental surge resistance ensures stable clamping during repetitive transients, while meeting MSL Level 1 per J-STD-020 and supporting peak forward surge current (IFSM) up to 200 A (8.3 ms half-sine).
Designed for unidirectional operation, it uses cathode-band polarity identification and delivers 0.106 %/°C temperature coefficient of VBR, enabling predictable voltage margining across automotive temperature ranges. The device is rated for 6.5 W steady-state power dissipation at TA = 50 °C on infinite heatsink.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins; defines safe DC rail margin for 72–80 V systems. |
| VBR @ IT = 1 mA | 86.7–95.8 V - Measured breakdown range confirming reliable avalanche initiation without premature conduction. |
| VC @ IPPM = 11.9 A | 126 V - Clamped voltage during 1500 W 10/1000 µs surge; determines maximum stress on downstream ICs. |
| PPPM | 1500 W - Peak pulse power handling capability; validates protection against ISO 7637-2 Pulse 1/2/5a/b and IEC 61000-4-5 surges. |
| RθJA | 75 °C/W - Junction-to-ambient thermal resistance on standard PCB pad layout; informs derating above 25 °C ambient. |
| IFSM | 200 A - Non-repetitive forward surge rating (8.3 ms); supports protection against load dump events in 24 V automotive systems. |
| TJ max. | +150 °C - Maximum junction temperature; enables use in under-hood environments with minimal thermal margin loss. |
Pinout & Package
Package: SMC (DO-214AB), surface-mount, low-profile case with matte tin-plated leads solderable per J-STD-002 and JESD 22-B102. Cathode identified by black band.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Current entry terminal in forward bias; connected to protected circuit ground or low-side return path | Enables unidirectional clamping from cathode to anode during overvoltage; must be routed to lowest-impedance ground plane. |
| Cathode | Current exit terminal in forward bias; marked with black band; connected to protected line (e.g., 78 V rail) | Defines polarity-sensitive connection - reverse connection disables clamping function and risks device failure. |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable leakage (<1 µA at VWM) and long-term reliability under humidity and thermal cycling. |
| MSL Level 1 rating | Supports lead-free reflow without preconditioning; compatible with standard SMT assembly at 260 °C peak. |
| RoHS-compliant (E3 suffix) | Meets EU Directive 2011/65/EU and JEDEC JESD201 Class 2 whisker resistance for high-reliability applications. |
| Low incremental surge resistance | Minimizes VC overshoot during fast-rising transients, improving protection margin for 75–100 V logic interfaces. |
| AEC-Q101 qualification option | HE3/HM3 variants available for automotive-grade validation; SMCJ78A-E3/9AT is commercial-grade but shares identical die and package. |
Applications
| Automotive Power Input Protection | Industrial DC Power Rail Clamp |
|---|---|
Use Scenario: Protecting 72–80 V battery-fed ECUs against load dump (ISO 7637-2 Pulse 5a) and alternator transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and DC-DC converter input. Use Value: Clamps 126 V at 11.9 A, limiting stress on upstream fuse and downstream regulator while surviving 200 A surge peaks. | Use Scenario: Safeguarding programmable logic controller (PLC) 75 V auxiliary power inputs from switching noise and inductive kickback. IC Role / Device Role / Timing Role: Standoff protector on field-side power entry, coordinated with upstream MOV and downstream LC filter. Use Value: 78 V VWM provides 3–5 V margin above nominal rail; 1500 W rating handles repeated 10/1000 µs surges without degradation. |
| Telecom Line Interface Surge Suppression | Motor Drive DC Bus Overvoltage Clamp |
Use Scenario: Shielding backplane power distribution in 48–72 V telecom shelf systems from hot-swap and lightning-induced surges. IC Role / Device Role / Timing Role: Primary clamp on mid-rail distribution node, located adjacent to connector entry point. Use Value: 126 V clamping voltage ensures downstream ASICs rated for 100 V abs max remain within safe operating area during IEC 61000-4-5 4 kV tests. | Use Scenario: Mitigating regenerative voltage spikes on 75 V DC bus of brushless motor drives during rapid deceleration. IC Role / Device Role / Timing Role: Parallel-connected TVS across bus terminals to absorb energy not captured by braking resistor. Use Value: 1500 W peak power rating absorbs short-duration spikes without thermal runaway; 0.106 %/°C VBR TC maintains consistent trip point across motor enclosure temperature swings. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SAC78A-E3/9AT | Same VWM/VBR/VC specs, but lower PPPM = 600 W and higher RθJA = 100 °C/W | Limited to lower-energy transients (e.g., ESD-only); unsuitable for ISO 7637-2 Pulse 5a | Select only when system-level surge testing requires <600 W clamping and space constraints prohibit SMC footprint. |
| SMCJ78CA-E3/9AT | Bidirectional variant with identical VWM/VBR/PPPM, but no polarity marking and symmetric clamping in both directions | Required for AC-coupled or floating signal lines where reverse polarity events occur | Choose only if protecting bidirectional data/power buses (e.g., CAN FD, RS-485) where unidirectional polarity cannot be guaranteed. |
Compared with SAC78A-E3/9AT and SMCJ78CA-E3/9AT, the SMCJ78A-E3/9AT uniquely balances 1500 W surge capacity, unidirectional polarity control, and industry-standard SMC thermal performance - making it optimal for fixed-polarity DC rail protection where high-energy transients dominate design requirements.
Availability
SMCJ78A-E3/9AT is available at Aetrix Electronics and suitable for automotive ECU power inputs, industrial PLC power rails, telecom shelf distribution nodes, and motor drive DC bus protection requiring stable component supply and full traceability.
Supply support for SMCJ78A-E3/9AT 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
Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, rectifiers, MOSFETs, and protection devices with emphasis on reliability, efficiency, and application-specific optimization.
The SMCJ series targets high-power transient suppression in harsh environments, engineered for automotive, industrial, and telecom systems demanding AEC-Q101 readiness, robust surge immunity, and consistent clamping performance across temperature.
FAQ
What is the clamping voltage of the SMCJ78A-E3/9AT at its rated peak pulse current?
The SMCJ78A-E3/9AT has a maximum clamping voltage (VC) of 126 V at 11.9 A peak pulse current (IPPM) under the standard 10/1000 µs waveform. This value is measured per ANSI/IEEE C62.35 and defines the upper voltage limit imposed on protected circuitry during a full-rated surge event. The SMCJ78A-E3/9AT maintains this clamping performance across its operational temperature range, ensuring predictable protection behavior in automotive and industrial deployments.
Is the SMCJ78A-E3/9AT suitable for automotive applications requiring AEC-Q101 qualification?
The SMCJ78A-E3/9AT itself is a commercial-grade part with E3 suffix (RoHS-compliant, non-automotive qualified). However, Vishay offers the functionally identical SMCJ78A-HE3_X variant, which carries full AEC-Q101 qualification for automotive use. Engineers selecting the SMCJ78A-E3/9AT for automotive designs must verify whether end-customer qualification requirements mandate certified parts - if so, the HE3 variant of SMCJ78A-E3/9AT should be specified instead.
How does the SMCJ78A-E3/9AT differ from the bidirectional SMCJ78CA-E3/9AT?
The SMCJ78A-E3/9AT is unidirectional with cathode-band polarity marking and conducts only during reverse-biased overvoltage events, whereas the SMCJ78CA-E3/9AT is bidirectional with no polarity marking and clamps symmetrically in both directions. Their VWM, VBR, PPPM, and VC values are identical, but the SMCJ78A-E3/9AT is intended for fixed-polarity DC rails, while the SMCJ78CA-E3/9AT suits AC-coupled or floating lines like CAN or RS-485. Using SMCJ78A-E3/9AT in bidirectional circuits risks failure during positive transients.
What is the thermal resistance and how does it affect PCB layout for the SMCJ78A-E3/9AT?
The SMCJ78A-E3/9AT has a typical junction-to-ambient thermal resistance (RθJA) of 75 °C/W when mounted on the recommended 0.31" × 0.31" (8.0 mm × 8.0 mm) copper pads per terminal. This value assumes no additional heatsinking; reducing pad size or using thinner copper increases RθJA, risking thermal runaway during sustained surge duty cycles. For high-reliability layouts, maintain minimum pad dimensions and consider internal ground planes to improve heat spreading - critical for applications involving repetitive transients.
Can the SMCJ78A-E3/9AT replace older SMAJ78A devices in existing designs?
The SMCJ78A-E3/9AT is not a direct drop-in replacement for SMAJ78A due to package differences: SMCJ uses DO-214AB (larger, higher power), while SMAJ uses DO-214AC (smaller, 400 W rating). Although both share identical VWM and VBR specs, the SMCJ78A-E3/9AT requires larger PCB pads, delivers 1500 W vs. 400 W, and exhibits lower RθJA. Layout changes are mandatory; however, upgrading to SMCJ78A-E3/9AT improves surge robustness in legacy designs where space allows and higher energy handling is needed.
SMCJ78A-E3/9AT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Package/Case:
- DO-214AB, SMC
- Series:
- TransZorb®
- 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:
- 126V
- Current - Peak Pulse (10/1000µs):
- 11.9A
- Power - Peak Pulse:
- 1500W (1.5kW)
- 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-214AB (SMCJ)
SMCJ78A-E3/9AT FAQ
1.How can I place an order for SMCJ78A-E3/9AT through Aetrix?
Please submit a Request for Quotation (RFQ) for SMCJ78A-E3/9AT 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 SMCJ78A-E3/9AT reliable?
The price and inventory of SMCJ78A-E3/9AT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMCJ78A-E3/9AT is usually 5 days.
3.What payment methods are accepted for SMCJ78A-E3/9AT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMCJ78A-E3/9AT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMCJ78A-E3/9AT?
SMCJ78A-E3/9AT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMCJ78A-E3/9AT 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 SMCJ78A-E3/9AT?
For technical support, including SMCJ78A-E3/9AT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMCJ78A-E3/9AT requirements.
6.How does Aetrix verify that SMCJ78A-E3/9AT is sourced from the original manufacturer or authorized distributors?
All SMCJ78A-E3/9AT 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 SMCJ78A-E3/9AT meets industry standards.
7.What is the process for return or replacement of SMCJ78A-E3/9AT?
All SMCJ78A-E3/9AT units undergo pre-shipment inspection (PSI). If there is an issue with SMCJ78A-E3/9AT, 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 SMCJ78A-E3/9AT part is unused and in its original packaging.
Return procedure for SMCJ78A-E3/9AT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMCJ78A-E3/9AT Tags
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