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Vishay General Semiconductor - Diodes Division SMAJ78A-M3/5A
- Part No.:
- SMAJ78A-M3/5A
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78A-M3/5A.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:7,007
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Product details
Overview
SMAJ78A-M3/5A from Vishay General Semiconductor is a unidirectional surface-mount Transient Voltage Suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping voltage transients on power and signal lines. 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 - used to protect MOSFETs, ICs, and sensor interfaces in industrial power supplies and automotive control modules.
For engineers reviewing the SMAJ78A-M3/5A datasheet, SMAJ78A-M3/5A pinout, SMAJ78A-M3/5A application, or SMAJ78A-M3/5A equivalent, key selection criteria include clamping performance under 3.2 A surge, thermal resistance (RθJA = 120 °C/W), unidirectional polarity marking, and halogen-free RoHS-compliant construction per M3 suffix.
Technical Context
This TVS diode operates as a fast-acting shunt protector, responding in <1 ps to overvoltage events and diverting transient energy to ground before downstream components are stressed. Its glass-passivated junction ensures stable leakage (<1 μA at 78 V) and repeatable breakdown behavior across temperature (-55 °C to +150 °C).
The device complies with AEC-Q101 when ordered with HE3/HM3 suffixes, but SMAJ78A-M3/5A is commercial-grade; it meets MSL Level 1 per J-STD-020 and supports automated SMT placement with matte tin-plated leads solderable per J-STD-002.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - maximum continuous reverse operating voltage before clamping begins |
| VBR min/max | 86.7 V / 95.8 V at 1 mA - guaranteed breakdown window defining turn-on threshold |
| VC @ IPPM | 126 V at 3.2 A - clamped voltage during 10/1000 μs surge, limiting stress on protected IC |
| PPPM | 400 W - peak pulse power handling capability with standard lightning-surge waveform |
| ID @ VWM | ≤1.0 μA - ultra-low reverse leakage preserves signal integrity in high-impedance circuits |
| RθJA | 120 °C/W - thermal resistance determines derating above 25 °C ambient for sustained reliability |
| Polarity | Unidirectional - cathode marked by band; blocks forward conduction beyond ~3.5 V |
Pinout & Package
Package: SMA (DO-214AC), surface-mount, low-profile case with matte tin-plated leads; dimensions: 4.50 mm × 2.79 mm × 2.29 mm (L × W × H); MSL Level 1, JEDEC-compliant footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential side (e.g., GND or return path) in unidirectional protection |
| Cathode | Reverse-biased clamping terminal | Marked by band; connected to line being protected (e.g., 78 V rail or signal trace) |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power | Handles IEC 61000-4-5 surge test levels without degradation when mounted on 5 mm × 5 mm copper pads |
| Glass-passivated junction | Ensures long-term stability of VBR and low parametric drift over temperature and life cycle |
| Halogen-free & RoHS-compliant (M3) | Meets IPC-1752A material declaration requirements and JESD201 Class 2 whisker resistance |
| Fast response time | Sub-nanosecond turn-on enables protection of high-speed logic and analog front-ends against ESD and switching spikes |
| Low incremental surge resistance | Minimizes voltage overshoot during initial transient rise, improving clamping fidelity |
Applications
| Industrial Power Supply Protection | Automotive Body Control Module |
|---|---|
Use Scenario: 78 V DC input rail in programmable logic controller (PLC) power stage exposed to relay-coil flyback and load dump. IC Role / Device Role / Timing Role: Unidirectional TVS placed between rail and chassis ground to clamp transients before they reach DC-DC controller ICs. Use Value: Limits voltage excursion to ≤126 V during 3.2 A surge, preventing latch-up or gate oxide damage in 80 V-rated MOSFETs and controllers. | Use Scenario: LIN bus line in door module subjected to ESD and battery disconnect transients. IC Role / Device Role / Timing Role: Standoff-clamp TVS on LIN data line referenced to local ground, protecting transceiver IC input pins. Use Value: Sub-1 ns response suppresses >8 kV contact ESD per IEC 61000-4-2 while maintaining <1 μA leakage at 12 V nominal operation. |
| Telecom Interface Protection | Consumer Sensor Hub Protection |
Use Scenario: 48 V PoE-powered Ethernet interface board experiencing induced surges from nearby AC wiring. IC Role / Device Role / Timing Role: Primary-level TVS on PSE-side DC input, upstream of DC-DC converter and PHY IC. Use Value: 400 W rating sustains multiple 10/1000 μs surges up to 3.2 A without parameter shift, ensuring long-term field reliability. | Use Scenario: 78 V bias supply for MEMS pressure sensor array in HVAC control unit exposed to HVAC motor switching noise. IC Role / Device Role / Timing Role: Rail-to-ground TVS on sensor analog supply line, placed adjacent to LDO input capacitor. Use Value: 126 V clamping prevents sensor ADC saturation and reference rail disturbance during 100 ns–1 μs transients. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ78A-E3/5A | Same electrical specs; RoHS-compliant but not halogen-free (E3 vs M3) | Acceptable where halogen-free requirement is not mandated (e.g., non-automotive commercial gear) | Select when cost sensitivity outweighs halogen-free compliance needs |
| SMAJ78CA-M3/5A | Bidirectional version; symmetric VBR (86.7–95.8 V) in both directions; no polarity marking | Required for AC-coupled or floating signal lines where reverse polarity transients occur | Choose only if bidirectional clamping is explicitly needed; not drop-in for unidirectional layouts |
Compared with SMAJ78A-M3/5A, the E3 variant offers identical protection performance without halogen-free assurance, while the 78CA variant changes circuit topology by removing polarity dependence - requiring layout review and functional validation before substitution.
Availability
SMAJ78A-M3/5A is available at Aetrix Electronics and suitable for industrial power supplies, automotive body electronics, and telecom interface designs requiring stable component supply with halogen-free compliance and MSL Level 1 handling.
Supply support for SMAJ78A-M3/5A 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, rectifiers, MOSFETs, and protection devices with emphasis on reliability, precision, and application-specific optimization.
The SMAJ series targets robust, surface-mount transient suppression for harsh environments - engineered for fast clamping, low leakage, and consistent performance across automotive, industrial, and telecom power rails.
FAQ
What is the maximum clamping voltage of SMAJ78A-M3/5A under a 10/1000 μs surge?
The SMAJ78A-M3/5A has a maximum clamping voltage (VC) of 126 V when subjected to its rated peak pulse current of 3.2 A with a 10/1000 μs waveform. This value is measured per Fig. 1 in the Vishay datasheet 88390 and defines the upper voltage limit imposed on protected circuitry during transient events. The SMAJ78A-M3/5A maintains this clamping performance across its specified operating temperature range.
Does SMAJ78A-M3/5A meet automotive qualification standards?
No - SMAJ78A-M3/5A is commercial-grade and not AEC-Q101 qualified. Vishay offers AEC-Q101 versions under ordering codes SMAJ78AHE3 or SMAJ78AHM3 (with HE3/HM3 suffixes). The SMAJ78A-M3/5A retains the same electrical characteristics and package but lacks the extended temperature cycling, humidity testing, and failure analysis required for automotive use. Always verify qualification status via the full part number before deployment in vehicle systems.
What does the "M3" suffix indicate in SMAJ78A-M3/5A?
The "M3" suffix in SMAJ78A-M3/5A denotes halogen-free, RoHS-compliant construction meeting IPC-1752A material declarations and JESD201 Class 2 whisker resistance. It distinguishes the part from E3 (RoHS-compliant but not halogen-free) and HM3 (halogen-free + AEC-Q101 qualified). The SMAJ78A-M3/5A uses matte tin-plated leads and UL 94 V-0 molding compound, making it suitable for environmentally regulated industrial and consumer applications.
How is polarity identified on SMAJ78A-M3/5A?
SMAJ78A-M3/5A is unidirectional and marked with a cathode band at one end of the SMA (DO-214AC) package. The banded end is the cathode and must be connected toward the line being protected (e.g., 78 V rail), while the anode connects to ground or lower potential. Bidirectional variants (e.g., SMAJ78CA) have no band marking. Correct orientation is essential - reverse installation renders the device ineffective for transient suppression.
What PCB pad layout is recommended for optimal thermal performance of SMAJ78A-M3/5A?
Vishay specifies a minimum 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pad for each terminal to achieve the rated 400 W peak pulse power. Smaller pads reduce heat dissipation and cause premature thermal runaway during repetitive surges. The SMAJ78A-M3/5A's RθJA of 120 °C/W assumes this layout; reducing pad area increases junction temperature and requires derating per Fig. 2 in datasheet 88390. Thermal vias under pads further improve performance in high-reliability designs.
SMAJ78A-M3/5A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Package/Case:
- DO-214AC, SMA
- Series:
- TransZorb®
- Packaging:
- Tape & Reel (TR)
- Product Status:
- 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):
- 3.2A
- Power - Peak Pulse:
- 400W
- 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-214AC (SMA)
SMAJ78A-M3/5A FAQ
1.How can I place an order for SMAJ78A-M3/5A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78A-M3/5A 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 SMAJ78A-M3/5A reliable?
The price and inventory of SMAJ78A-M3/5A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78A-M3/5A is usually 5 days.
3.What payment methods are accepted for SMAJ78A-M3/5A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78A-M3/5A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78A-M3/5A?
SMAJ78A-M3/5A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78A-M3/5A 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 SMAJ78A-M3/5A?
For technical support, including SMAJ78A-M3/5A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78A-M3/5A requirements.
6.How does Aetrix verify that SMAJ78A-M3/5A is sourced from the original manufacturer or authorized distributors?
All SMAJ78A-M3/5A 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 SMAJ78A-M3/5A meets industry standards.
7.What is the process for return or replacement of SMAJ78A-M3/5A?
All SMAJ78A-M3/5A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78A-M3/5A, 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 SMAJ78A-M3/5A part is unused and in its original packaging.
Return procedure for SMAJ78A-M3/5A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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