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Alpha & Omega Semiconductor Inc. SMDJ78A
- Part No.:
- SMDJ78A
- Manufacturer:
- Alpha & Omega Semiconductor Inc.
- Category:
- TVS Diodes
- Package:
- DO-214AB, SMC
- Datasheet:
-
SMDJ78A.pdf
- Description:
- 1CH 78V UNIDIRECTIONAL 3000W SMD
- Quantity:
- Payment:
- Shipping:
Inventory:2,951
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Product details
Overview
SMDJ78A from Alpha & Omega Semiconductor is a unidirectional transient voltage suppressor diode (TVS) designed for high-energy ESD and surge protection in DC power rails and signal lines. It features a 78.0 V reverse standoff voltage (VRWM), 86.7–95.8 V breakdown voltage (VBR) at 1 mA, 126.0 V maximum clamping voltage (VC) at 23.9 A peak pulse current, and 3000 W peak pulse power dissipation on a 10/1000 µs waveform - suitable for industrial power supply input protection.
For engineers reviewing the SMDJ78A datasheet, pinout, applications, or equivalent options, key selection criteria include unidirectional polarity, DO-214AB package compatibility, clamping performance under IEC 61000-4-5 surge conditions, thermal resistance (RθJA = 75 °C/W), and junction temperature limits up to +150 °C.
Technical Context
The SMDJ78A operates as a silicon avalanche diode with glass-passivated junction and low-profile DO-214AB (SMC J-Bend) surface-mount package. Its fast response time (<1.0 ps) enables suppression of sub-nanosecond transients, while its 0.01% duty cycle repetition rate supports infrequent but high-energy surges.
Designed for unidirectional operation, it uses a cathode band marking for polarity identification and exhibits a typical temperature coefficient of ΔVBR = 0.1% × VBR per °C change from 25 °C. Thermal performance is specified with 8.0 mm × 8.0 mm copper pads, yielding RθJL = 15 °C/W and RθJA = 75 °C/W.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 78.0 V - Maximum continuous reverse operating voltage before clamping begins; defines safe DC rail margin. |
| VBR @ IT=1mA | 86.7–95.8 V - Measured breakdown range ensures reliable turn-on during overvoltage events. |
| VC @ IPPM | 126.0 V - Clamped voltage at 23.9 A peak pulse current; determines protected circuit's maximum stress level. |
| PPPM (10/1000µs) | 3000 W - Peak surge energy handling capacity; validates compliance with IEC 61000-4-5 Level 4 (4 kV/2 Ω). |
| TJ max | +150 °C - Maximum junction temperature; sets thermal derating boundary for sustained operation. |
| Polarity | Unidirectional - Requires correct orientation relative to DC rail polarity; cathode band denotes anode-to-cathode direction. |
| Package | DO-214AB (SMC J-Bend) - Standardized surface-mount outline with J-bent leads; compatible with automated pick-and-place and reflow. |
Pinout & Package
DO-214AB (SMC J-Bend) package with two terminals: anode and cathode. Cathode identified by color band. Molded plastic case, matte tin lead-free plating, UL 94V-0 flammability rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | DC return / ground reference terminal | Connected to lower-potential side of protected line; completes clamping path during reverse surge. |
| Cathode | Protected line connection | Marked with color band; connects to positive rail or signal line; avalanche conduction occurs when voltage exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| Fast response time | <1.0 ps - Enables suppression of nanosecond-scale ESD and lightning-induced transients before downstream IC damage occurs. |
| Glass passivated junction | Enhanced reliability and stable VBR over lifetime - reduces parameter drift and leakage degradation under thermal cycling. |
| Built-in strain relief | Mechanical robustness against board flexure and thermal expansion mismatch - prevents solder joint fatigue in harsh environments. |
| MSL1 moisture sensitivity | Compatible with standard SMT reflow profiles up to 260 °C peak - eliminates pre-bake requirement and streamlines manufacturing. |
| Low profile package | Height ≤2.6 mm - enables use in space-constrained power modules and compact industrial controllers without height interference. |
Applications
| Industrial PLC Power Input | Telecom DC Feeder Protection |
|---|---|
Use Scenario: 48 V DC power feeders in outdoor telecom cabinets exposed to induced lightning surges and AC coupling faults. IC Role / Device Role / Timing Role: Unidirectional TVS diode placed across input terminals to clamp surges before they reach DC-DC converters and monitoring circuitry. Use Value: 3000 W PPPM and 126.0 V VC ensure system-level immunity to IEC 61000-4-5 4 kV surge tests without upstream fuse blowing. | Use Scenario: 24 V DC auxiliary power rail in programmable logic controllers subjected to relay coil flyback and field wiring transients. IC Role / Device Role / Timing Role: Primary overvoltage clamp on main power bus, coordinated with upstream fuse and downstream ceramic capacitors. Use Value: 86.7–95.8 V VBR tolerance allows precise coordination with 24 V nominal rail +20% tolerance and 30 V brown-out thresholds. |
| Motor Drive DC Bus Protection | Renewable Energy Inverter DC Link |
Use Scenario: DC link between rectifier and IGBT H-bridge in variable frequency drives, subject to regenerative energy spikes and switching noise. IC Role / Device Role / Timing Role: Transient suppressor mounted directly at DC bus capacitor terminals to limit voltage overshoot during rapid load changes. Use Value: 150 °C TJ max and RθJA = 75 °C/W enable stable operation near heat-generating power stages without thermal runaway. | Use Scenario: PV string combiner box DC output feeding central inverter, exposed to long-line induced surges and ground potential rise. IC Role / Device Role / Timing Role: First-stage surge protector on DC output bus, sized to absorb multi-kW pulses before MOV-based secondary protection activates. Use Value: DO-214AB footprint allows parallel placement with high-current bus bars and integration into UL-listed enclosures without creepage clearance violations. |
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 | Same VRWM (78 V), but lower PPPM (1500 W); TO-220AC package with higher RθJA (~100 °C/W). | Requires heatsinking for repeated surges; unsuitable for high-density SMT layouts. | Select only if through-hole mounting and thermal mass availability permit. |
| SMCJ78A | Identical electrical specs and DO-214AB package; same 3000 W PPPM and 126 V VC, but from different manufacturer (e.g., Vishay). | No functional or layout change required; validated in same IEC test configurations. | Drop-in alternative where dual-sourcing or qualification flexibility is needed. |
Compared with SAC78A, SMDJ78A offers double the surge power rating and superior thermal performance in surface-mount form; compared with SMCJ78A, it provides identical protection capability with AOS-specific process control and green compliance (halogen-free, RoHS).
Availability
SMDJ78A is available at Aetrix Electronics and suitable for industrial PLC power input, telecom DC feeder protection, and motor drive DC bus protection requiring stable component supply, long-term lifecycle support, and consistent surge performance across production batches.
Supply support for SMDJ78A 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
Alpha & Omega Semiconductor (AOS) is a fabless power semiconductor company specializing in MOSFETs, TVS diodes, and power ICs for high-efficiency power conversion and protection.
The SMDJ78A belongs to AOS's SMDJ series of high-power surface-mount TVS diodes, engineered specifically for robust, single-pulse surge immunity in industrial, telecom, and renewable energy systems where reliability under extreme transient stress is critical.
FAQ
What is the maximum clamping voltage of the SMDJ78A under a 10/1000 µs surge?
The SMDJ78A has a maximum clamping voltage (VC) of 126.0 V when subjected to its rated peak pulse current of 23.9 A on a 10/1000 µs waveform. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuitry during surge events - critical for ensuring downstream components like DC-DC controllers remain within absolute maximum ratings. The SMDJ78A maintains this clamping performance across its full operating temperature range.
Is the SMDJ78A suitable for bidirectional surge protection?
No, the SMDJ78A is a unidirectional TVS diode and must be oriented with its cathode toward the positive side of the protected DC line. For bidirectional applications, the SMDJ78CA variant is specified - it provides symmetrical clamping in both polarities. Using SMDJ78A in reverse-biased configuration will not provide effective protection and may result in device failure. Always verify polarity marking (cathode band) before PCB layout.
What is the thermal resistance of the SMDJ78A when mounted on standard PCB copper pads?
When mounted on 8.0 mm × 8.0 mm copper pads per terminal, the SMDJ78A exhibits a typical junction-to-ambient thermal resistance (RθJA) of 75 °C/W and a junction-to-lead resistance (RθJL) of 15 °C/W. These values assume JEDEC-standard test conditions and are essential for calculating steady-state temperature rise under leakage current or repetitive low-duty-cycle surges. Derating curves in the datasheet must be applied above 25 °C ambient.
Does the SMDJ78A meet RoHS and halogen-free requirements?
Yes, the SMDJ78A is an AOS Green Product: fully RoHS compliant, lead-free, and halogen-free per AOS' published Green Policy. It meets UL 94V-0 flammability standards and uses matte tin lead-free plating compatible with standard Pb-free reflow profiles. Full compliance documentation, including material declarations and test reports, is available via AOS' website and authorized distribution channels for the SMDJ78A.
How does the SMDJ78A compare to the SMCJ78A in terms of package and performance?
The SMDJ78A and SMCJ78A share identical DO-214AB (SMC J-Bend) packaging, 78.0 V VRWM, 3000 W PPPM, and 126.0 V VC specifications - making them functionally interchangeable in layout and electrical behavior. Differences lie in manufacturer-specific process control, qualification testing, and compliance documentation. The SMDJ78A reflects AOS' design and process validation, while SMCJ78A represents Vishay's implementation; both meet IEC 61000-4-5 Level 4 requirements.
SMDJ78A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Alpha & Omega Semiconductor Inc.
- Package/Case:
- DO-214AB, SMC
- Series:
- -
- 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):
- 23.9A
- Power - Peak Pulse:
- 3000W (3kW)
- 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
SMDJ78A FAQ
1.How can I place an order for SMDJ78A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMDJ78A 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 SMDJ78A reliable?
The price and inventory of SMDJ78A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMDJ78A is usually 5 days.
3.What payment methods are accepted for SMDJ78A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMDJ78A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMDJ78A?
SMDJ78A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMDJ78A 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 SMDJ78A?
For technical support, including SMDJ78A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMDJ78A requirements.
6.How does Aetrix verify that SMDJ78A is sourced from the original manufacturer or authorized distributors?
All SMDJ78A 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 SMDJ78A meets industry standards.
7.What is the process for return or replacement of SMDJ78A?
All SMDJ78A units undergo pre-shipment inspection (PSI). If there is an issue with SMDJ78A, 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 SMDJ78A part is unused and in its original packaging.
Return procedure for SMDJ78A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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