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Vishay General Semiconductor - Diodes Division SMAJ78AHE3/5A
- Part No.:
- SMAJ78AHE3/5A
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78AHE3/5A.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:9,428
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Product details
Overview
SMAJ78AHE3/5A from Vishay General Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed to protect sensitive electronics against voltage transients induced by inductive load switching and lightning surges. It features a 78 V stand-off voltage (VWM), 86.7–95.8 V breakdown voltage (VBR) at 1 mA, 126 V maximum clamping voltage (VC) at 3.2 A peak pulse current, and 400 W peak pulse power rating with 10/1000 μs waveform.
For engineers reviewing the SMAJ78AHE3/5A datasheet, SMAJ78AHE3/5A pinout, SMAJ78AHE3/5A application, or SMAJ78AHE3/5A equivalent, key selection criteria include its AEC-Q101 qualification for automotive use, low incremental surge resistance, fast response time, and compatibility with automated SMT placement on PCBs requiring robust overvoltage protection for DC power rails and signal lines.
Technical Context
The SMAJ78AHE3/5A operates as a unidirectional avalanche diode, conducting only in reverse bias above VBR to clamp transient energy into ground. Its glass-passivated junction ensures stable breakdown characteristics and long-term reliability under repetitive surge stress.
Rated for 40 A peak forward surge current (IFSM, 8.3 ms half-sine), it supports high-energy transient suppression while maintaining low leakage (<1.0 μA at 78 V) and thermal resistance of 120 °C/W (junction-to-ambient). The device is qualified per AEC-Q101 and meets MSL Level 1 reflow requirements (260 °C peak).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - Maximum continuous reverse operating voltage before clamping begins; defines safe DC rail protection threshold. |
| VBR min/max | 86.7 V / 95.8 V at 1 mA - Confirmed breakdown range ensures predictable turn-on during transients without premature conduction. |
| VC @ IPPM | 126 V at 3.2 A - Clamping voltage limits downstream IC/MOSFET stress during 10/1000 μs surge events. |
| PPPM | 400 W - Peak pulse power handling capacity for standard lightning/surge waveforms; derated to 300 W above 78 V per spec. |
| IFSM | 40 A - Withstands single 8.3 ms half-sine surge, enabling protection of power supply inputs and motor drivers. |
| TJ max | +150 °C - Enables operation in under-hood automotive environments and industrial enclosures with elevated ambient temperatures. |
| Package | SMA (DO-214AC) - Standardized surface-mount outline with 5.0 mm × 5.0 mm copper pad thermal design support. |
Pinout & Package
Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads; cathode indicated by band marking on unidirectional devices.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to system ground or low-side return path; enables reverse-biased clamping operation when cathode is at higher potential. |
| Cathode | Transient clamping terminal | Connected to protected line (e.g., 78 V rail); conducts avalanche current to anode during overvoltage events to limit voltage excursion. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive-grade reliability including temperature cycling, humidity, and mechanical shock per JESD22 standards. |
| 400 W peak pulse power | Handles IEC 61000-4-5 Level 4 surge (4 kV/2 Ω) on 78 V DC systems with margin when mounted on recommended 5.0 mm × 5.0 mm copper pads. |
| Glass passivated junction | Ensures stable VBR tolerance and low leakage drift over lifetime and temperature, critical for long-term protection integrity. |
| MSL Level 1 | Compatible with standard lead-free reflow profiles up to 260 °C peak, eliminating moisture sensitivity concerns in manufacturing. |
| Low profile SMA package | 0.208" × 0.157" footprint enables compact placement near connectors, power inputs, and sensor interfaces without board area penalty. |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface Protection |
|---|---|
|
Use Scenario: Protecting 72–80 V battery-fed ECUs, ADAS modules, and body control units from load dump and alternator transients. IC Role / Device Role / Timing Role: Unidirectional TVS placed between battery rail and input filter capacitor to clamp spikes up to 126 V within nanoseconds. Use Value: Prevents damage to downstream DC/DC converters and microcontrollers during ISO 7637-2 Pulse 5a (load dump) events. |
Use Scenario: Safeguarding analog sensor outputs (e.g., pressure, temperature) connected to 78 V auxiliary supplies in factory automation systems. IC Role / Device Role / Timing Role: TVS shunt device on sensor VCC line, triggered only during ESD or inductive kickback exceeding 86.7 V. Use Value: Maintains signal integrity by limiting voltage overshoot to ≤126 V, preserving ADC accuracy and preventing latch-up in signal conditioning ICs. |
| Telecom DC Power Input Protection | Motor Drive DC Bus Snubbing |
|
Use Scenario: Securing -48 V telecom rectifier outputs upgraded to 78 V nominal for higher efficiency, exposed to lightning-induced surges on outdoor plant wiring. IC Role / Device Role / Timing Role: Primary clamping element on input stage, absorbing 10/1000 μs transients before they reach upstream MOSFETs and controllers. Use Value: Delivers 400 W surge handling with <1 ns response, meeting GR-1089-CORE Zone 3 immunity requirements for central office equipment. |
Use Scenario: Suppressing flyback voltage spikes from brushed DC motors or solenoids switched by 78 V-rated MOSFETs in material handling equipment. IC Role / Device Role / Timing Role: Parallel-connected TVS across motor terminals or MOSFET drain-source, conducting only during inductive turn-off transients. Use Value: Limits VDS stress to 126 V, extending MOSFET lifetime and eliminating need for larger, costlier active snubbers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ78A-E3/5A | Commercial-grade version without AEC-Q101 qualification; identical electrical specs and SMA package. | Approved for non-automotive industrial/commercial use only; not validated for automotive temperature cycling or vibration. | Select when automotive qualification is unnecessary and cost optimization is prioritized. |
| SMAJ78CAHE3/5A | Bidirectional variant with same VWM (78 V), symmetric clamping in both polarities, no polarity marking. | Required for AC-coupled or floating signal lines where reverse polarity transients occur; unsuitable for DC rail protection with defined ground reference. | Choose only when bidirectional surge immunity is mandatory, e.g., RS-485 data lines or transformer-coupled interfaces. |
Compared with SMAJ78A-E3/5A, the SMAJ78AHE3/5A adds AEC-Q101 qualification for automotive deployment, while SMAJ78CAHE3/5A trades unidirectional clamping precision for symmetrical bipolar protection-neither offers pin-compatible replacement without circuit review due to polarity and qualification scope differences.
Availability
SMAJ78AHE3/5A is available at Aetrix Electronics and suitable for automotive ECU protection, industrial sensor interface hardening, and telecom DC input surge suppression requiring stable component supply, traceable sourcing, and long-term lifecycle support.
Supply support for SMAJ78AHE3/5A 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, MOSFETs, optoelectronics, and passive components with emphasis on reliability and application-specific performance.
The SMAJ series is engineered for high-energy transient suppression in harsh environments, targeting automotive, industrial, and telecom applications where robust overvoltage protection is mission-critical.
FAQ
What is the clamping voltage of SMAJ78AHE3/5A at its rated peak pulse current?
The SMAJ78AHE3/5A has a maximum clamping voltage (VC) of 126 V at 3.2 A peak pulse current (IPPM) under the standard 10/1000 μs waveform. This value is measured per JEDEC test conditions and defines the upper voltage limit imposed on protected circuits during surge events. The SMAJ78AHE3/5A maintains this clamping performance across its qualified operating temperature range.
Is SMAJ78AHE3/5A suitable for automotive applications?
Yes, SMAJ78AHE3/5A is AEC-Q101 qualified, making it suitable for automotive applications including engine control units, body electronics, and ADAS modules. Its qualification covers temperature cycling, humidity testing, and mechanical shock per JESD22 standards. The "HE3" suffix explicitly denotes AEC-Q101 compliance, distinguishing it from commercial-grade variants like SMAJ78A-E3/5A.
How does the SMAJ78AHE3/5A differ from SMAJ78CAHE3/5A?
The SMAJ78AHE3/5A is unidirectional with cathode marking and clamps only in reverse bias, while SMAJ78CAHE3/5A is bidirectional with no polarity marking and clamps symmetrically in both directions. Their VWM and VBR values match, but SMAJ78CAHE3/5A is intended for AC or floating signal lines-not DC power rails with fixed ground reference-so direct substitution requires circuit validation.
What is the thermal resistance of SMAJ78AHE3/5A and how does it affect layout?
The SMAJ78AHE3/5A has a typical junction-to-ambient thermal resistance (RθJA) of 120 °C/W when mounted on minimum recommended 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. To maintain safe junction temperature under sustained power dissipation, PCB layout must allocate adequate copper area and avoid thermal bottlenecks-especially critical during repetitive surge events or elevated ambient temperatures.
Does SMAJ78AHE3/5A require special handling during reflow soldering?
No, SMAJ78AHE3/5A is rated MSL Level 1 per J-STD-020 and supports standard lead-free reflow profiles with a maximum peak temperature of 260 °C. Its matte tin-plated leads comply with J-STD-002 and JESD22-B102 for solderability, and whisker resistance is certified per JESD201 Class 2-no baking or special moisture precautions are required prior to assembly.
SMAJ78AHE3/5A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Package/Case:
- DO-214AC, SMA
- Series:
- TransZorb®
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- 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):
- 3.2A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ78AHE3/5A FAQ
1.How can I place an order for SMAJ78AHE3/5A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78AHE3/5A 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 SMAJ78AHE3/5A reliable?
The price and inventory of SMAJ78AHE3/5A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78AHE3/5A is usually 5 days.
3.What payment methods are accepted for SMAJ78AHE3/5A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78AHE3/5A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78AHE3/5A?
SMAJ78AHE3/5A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78AHE3/5A 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 SMAJ78AHE3/5A?
For technical support, including SMAJ78AHE3/5A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78AHE3/5A requirements.
6.How does Aetrix verify that SMAJ78AHE3/5A is sourced from the original manufacturer or authorized distributors?
All SMAJ78AHE3/5A 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 SMAJ78AHE3/5A meets industry standards.
7.What is the process for return or replacement of SMAJ78AHE3/5A?
All SMAJ78AHE3/5A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78AHE3/5A, 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 SMAJ78AHE3/5A part is unused and in its original packaging.
Return procedure for SMAJ78AHE3/5A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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