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Vishay General Semiconductor - Diodes Division SMAJ78A-E3/61
- Part No.:
- SMAJ78A-E3/61
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78A-E3/61.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:669
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Product details
Overview
SMAJ78A-E3/61 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 (IPPM), and 400 W peak pulse power rating (10/1000 μs waveform) - suitable for protecting MOSFETs, ICs, and sensor interfaces in industrial power supplies.
For engineers reviewing the SMAJ78A-E3/61 datasheet, SMAJ78A-E3/61 pinout, SMAJ78A-E3/61 application, or SMAJ78A-E3/61 equivalent, key selection criteria include clamping performance under 3.2 A surge, thermal resistance (RθJA = 120 °C/W), unidirectional polarity with cathode band marking, RoHS-compliant matte tin plating, and compatibility with automated SMT placement on 5.0 mm × 5.0 mm copper pads.
Technical Context
The SMAJ78A-E3/61 operates as a silicon avalanche diode with glass-passivated junction, delivering fast response time (<1 ns) to transient overvoltages. Its unidirectional configuration enables forward conduction only during reverse-biased clamping events, with cathode-end polarity marking for correct PCB orientation.
It is rated for 400 W peak pulse power (10/1000 μs) up to 78 V, derating to 300 W above 78 V per Vishay's specification; maximum junction temperature is 150 °C, and it meets MSL Level 1 per J-STD-020 with 260 °C reflow peak.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 78 V - maximum continuous reverse operating voltage before clamping initiates |
| VBR min/max | 86.7 V / 95.8 V at IT = 1 mA - ensures reliable avalanche breakdown within defined tolerance band |
| VC @ IPPM | 126 V at 3.2 A - clamping voltage limits downstream component stress during 10/1000 μs surge |
| PPPM | 400 W (≤78 V), 300 W (>78 V) - peak transient energy absorption capability with defined waveform |
| ID @ VWM | 1.0 μA - ultra-low leakage preserves system efficiency in standby and low-power modes |
| RθJA | 120 °C/W - thermal resistance dictates required PCB copper area (0.2" × 0.2") for safe 3.3 W steady-state dissipation |
| Package | SMA (DO-214AC) - industry-standard surface-mount outline with 2.54 mm lead pitch and MSL-1 reflow compatibility |
Pinout & Package
Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads; cathode indicated by a visible band on one end. Mounting requires 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal for rated power handling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward current entry / reverse surge return path | Connected to protected line ground or low-side reference; must be routed with low-inductance trace |
| Cathode | Avalanche clamping node / high-side connection | Marked with band; connects to line under protection (e.g., 78 V rail); determines unidirectional polarity |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power (10/1000 μs) | Enables robust protection against IEC 61000-4-5 Level 3 surges (1 kV/2 Ω) on 78 V DC rails without derating |
| Glass-passivated chip junction | Ensures stable VBR over lifetime and improved humidity resistance vs. epoxy-passivated alternatives |
| MSL Level 1, 260 °C peak reflow | Supports single-pass lead-free reflow without preconditioning or special handling in high-volume SMT lines |
| Low incremental surge resistance | Minimizes VC overshoot during fast-rising transients (e.g., inductive switch-off), improving clamping precision |
| RoHS-compliant, commercial grade (E3 suffix) | Meets global environmental compliance requirements without halogen content restrictions or automotive qualification overhead |
Applications
| Industrial Power Supply Protection | Automotive Body Control Module (BCM) Input |
|---|---|
|
Use Scenario: 78 V auxiliary supply rail in programmable logic controller (PLC) power stage exposed to relay coil flyback and ESD. IC Role / Device Role / Timing Role: Unidirectional TVS clamping device placed across input capacitor to limit transient voltage to ≤126 V during 3.2 A surges. Use Value: Prevents damage to upstream DC-DC controller ICs and downstream 78 V-rated MOSFET drivers during repetitive inductive switching events. |
Use Scenario: 78 V battery-fed input to BCM microcontroller power domain in commercial vehicle systems. IC Role / Device Role / Timing Role: Primary overvoltage clamp on main power entry, activated within <1 ns of load dump or jump-start transients. Use Value: Maintains system uptime by limiting voltage excursion below MCU absolute maximum rating (130 V) during ISO 7637-2 Pulse 5a events. |
| Telecom Remote Radio Unit (RRU) DC Feed | Industrial Sensor Signal Conditioning Interface |
|
Use Scenario: 78 V DC power feed over coaxial cable to remote radio head, subject to lightning-induced surges. IC Role / Device Role / Timing Role: First-stage transient suppressor at RRU power entry, coordinated with secondary MOV/GDT stages. Use Value: Absorbs initial 400 W surge energy while preserving coordination margin for downstream protection components. |
Use Scenario: 78 V bias supply for piezoelectric sensor amplifier in high-voltage industrial monitoring equipment. IC Role / Device Role / Timing Role: Standoff-clamp protector on amplifier VDD rail, ensuring signal integrity during EFT bursts (IEC 61000-4-4). Use Value: Limits rail collapse to <126 V, preventing amplifier latch-up and maintaining analog output accuracy during 5 kHz burst noise. |
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-M3/61 | Halogen-free, RoHS-compliant variant with identical electrical specs and SMA package | Required where halogen-free material compliance is mandated (e.g., EU public infrastructure projects) | Select when halogen-free certification is contractually required; otherwise, E3/61 offers same protection performance at lower cost |
| SMAJ78AHE3_A/H | AEC-Q101 qualified version with same VWM/VBR/VC ratings; differs in qualification testing and traceability | Required for automotive front-end modules, body electronics, or ADAS subsystems needing automotive-grade reliability | Choose only if AEC-Q101 qualification is mandatory; HE3 adds qualification overhead but no electrical benefit for industrial use |
Compared with SMAJ78A-E3/61, the M3/61 variant satisfies halogen-free mandates without altering clamping behavior, while the HE3_A/H version adds automotive qualification rigor but introduces higher cost and longer lead times - neither offers improved surge handling or thermal performance.
Availability
SMAJ78A-E3/61 is available at Aetrix Electronics and suitable for industrial power supplies, telecom remote units, automotive body control modules, and sensor interface protection requiring stable component supply and full traceability.
Supply support for SMAJ78A-E3/61 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, power efficiency, and application-specific optimization.
The SMAJ series was developed for high-reliability transient suppression in space-constrained SMT designs, targeting industrial, telecom, and automotive markets where consistent clamping performance and automated assembly compatibility are critical.
FAQ
What is the maximum clamping voltage of the SMAJ78A-E3/61 under standard test conditions?
The SMAJ78A-E3/61 has a maximum clamping voltage (VC) of 126 V at 3.2 A peak pulse current (IPPM), measured with a 10/1000 μs waveform. This value defines the upper voltage limit imposed on protected circuitry during transient events and is confirmed in Vishay's datasheet revision 09-Jan-2024, page 2. The SMAJ78A-E3/61 maintains this clamping performance across its specified operating temperature range.
Is the SMAJ78A-E3/61 suitable for bidirectional transient protection?
No, the SMAJ78A-E3/61 is a unidirectional TVS diode, indicated by the "A" suffix and cathode band marking. It conducts only in reverse bias during clamping and blocks forward current. For bidirectional protection, the SMAJ78CA variant must be used. The SMAJ78A-E3/61 datasheet explicitly states polarity as unidirectional and provides no bidirectional electrical characteristics.
What is the thermal resistance and recommended PCB layout for the SMAJ78A-E3/61?
The SMAJ78A-E3/61 has a typical junction-to-ambient thermal resistance (RθJA) of 120 °C/W, measured on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. To achieve rated 400 W pulse power, the PCB must provide these minimum pad dimensions with internal or external copper planes. The SMAJ78A-E3/61 thermal performance degrades significantly with smaller pads or insufficient copper area.
Does the SMAJ78A-E3/61 meet automotive qualification standards?
The SMAJ78A-E3/61 is a commercial-grade part (E3 suffix) and is not AEC-Q101 qualified. For automotive applications, Vishay offers the SMAJ78AHE3_A/H variant, which carries AEC-Q101 qualification. The SMAJ78A-E3/61 datasheet confirms E3 as RoHS-compliant commercial grade only, with no mention of automotive stress testing or qualification data.
What is the reverse leakage current of the SMAJ78A-E3/61 at its rated standoff voltage?
The SMAJ78A-E3/61 exhibits a maximum reverse leakage current (ID) of 1.0 μA at its 78 V stand-off voltage (VWM), measured at TA = 25 °C. This low leakage ensures minimal power loss in always-on circuits and avoids unintended loading of high-impedance sensor bias networks. The value is specified in the Electrical Characteristics table on page 2 of the Vishay datasheet.
SMAJ78A-E3/61 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-E3/61 FAQ
1.How can I place an order for SMAJ78A-E3/61 through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78A-E3/61 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-E3/61 reliable?
The price and inventory of SMAJ78A-E3/61 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78A-E3/61 is usually 5 days.
3.What payment methods are accepted for SMAJ78A-E3/61?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78A-E3/61 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78A-E3/61?
SMAJ78A-E3/61 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78A-E3/61 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-E3/61?
For technical support, including SMAJ78A-E3/61 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78A-E3/61 requirements.
6.How does Aetrix verify that SMAJ78A-E3/61 is sourced from the original manufacturer or authorized distributors?
All SMAJ78A-E3/61 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-E3/61 meets industry standards.
7.What is the process for return or replacement of SMAJ78A-E3/61?
All SMAJ78A-E3/61 units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78A-E3/61, 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-E3/61 part is unused and in its original packaging.
Return procedure for SMAJ78A-E3/61:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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