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Vishay General Semiconductor - Diodes Division SMAJ78A-E3/5A
- Part No.:
- SMAJ78A-E3/5A
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ78A-E3/5A.pdf
- Description:
- TVS DIODE 78VWM 126VC DO214AC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SMAJ78A-E3/5A 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, and clamps to ≤126 V at 3.2 A peak pulse current under 10/1000 μs waveform - used in automotive power rail protection and industrial sensor interface circuits.
For engineers reviewing the SMAJ78A-E3/5A datasheet, SMAJ78A-E3/5A pinout, SMAJ78A-E3/5A application, or SMAJ78A-E3/5A equivalent, key selection criteria include its 400 W peak pulse power rating (≤78 V), low 0.057 %/°C VBR temperature coefficient, AEC-Q101 qualification eligibility (via HE3 suffix), and compatibility with automated SMT placement on 5.0 mm × 5.0 mm copper pads.
Technical Context
This unidirectional TVS diode operates by avalanche breakdown to limit transient overvoltages before they damage downstream ICs or MOSFETs. Its glass-passivated junction ensures stable leakage (<1.0 μA at VWM) and fast response time (<1.0 ns), while the SMA package provides 120 °C/W junction-to-ambient thermal resistance under standard PCB layout.
The device complies with ANSI/IEEE C62.35 surge standards and delivers 3.2 A peak pulse current (IPPM) at 126 V clamping voltage (VC) with 10/1000 μs waveform. Derating applies above 25 °C ambient per Fig. 2, and maximum forward surge current is 40 A (8.3 ms half-sine) - applicable only in unidirectional configuration.
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 1.0 mA - guaranteed avalanche initiation range for reliable overvoltage detection |
| VC @ IPPM | ≤126 V at 3.2 A - clamped voltage during 10/1000 μs surge, defining protected circuit's max stress level |
| PPPM | 400 W - peak pulse power handling capability (derated to 300 W above 78 V per spec note) |
| IFSM | 40 A - non-repetitive forward surge current rating (8.3 ms half-sine), critical for inrush or load-dump events |
| TJ max | +150 °C - maximum junction temperature, enabling operation in under-hood automotive environments |
| Package | SMA (DO-214AC) - industry-standard surface-mount outline with cathode band marking and 0.064 g unit weight |
Pinout & Package
Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads, MSL Level 1 (260 °C reflow peak), UL 94 V-0 rated compound. Polarity indicated by cathode band on unidirectional devices like SMAJ78A-E3/5A.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential side of protected line; conducts during forward surge (e.g., load dump) |
| Cathode | Avalanche clamping terminal | Connected to higher-potential side; initiates breakdown when reverse voltage exceeds VBR |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power (10/1000 μs) | Enables robust protection against ISO 7637-2 Pulse 1/2a/5a and IEC 61000-4-5 surges in 12 V/24 V systems |
| Low clamping ratio (VC/VBR ≈ 1.32) | Minimizes voltage overshoot during transients, reducing stress on downstream 80 V-rated MOSFETs or regulators |
| 0.057 %/°C VBR tempco | Ensures stable breakdown threshold across -55 °C to +150 °C, critical for engine bay or industrial control applications |
| AEC-Q101 qualification path | Supports automotive-grade sourcing via HE3/HM3 suffix variants, meeting stress test requirements for passenger vehicles |
| MSL Level 1 moisture sensitivity | Allows unlimited floor life and standard reflow without baking, simplifying high-volume SMT manufacturing |
Applications
| Automotive Power Rail Protection | Industrial Sensor Signal Line Guarding |
|---|---|
|
Use Scenario: Suppresses load dump transients (up to 120 V, 100 ms) on 24 V battery-fed ECUs in commercial vehicles. IC Role / Device Role / Timing Role: Unidirectional TVS placed between power input and ground, clamping within <1 ns to protect DC-DC converters and microcontrollers. Use Value: Limits peak voltage to ≤126 V during 3.2 A surge, preventing latch-up or gate oxide rupture in 36 V-input buck controllers. |
Use Scenario: Shields analog output lines (e.g., 4–20 mA current loop) from ESD and inductive switching noise in factory automation PLCs. IC Role / Device Role / Timing Role: Mounted directly at connector entry point, shunting transients before reaching op-amp input stages or ADC front-ends. Use Value: Maintains signal integrity with <1.0 μA leakage at 78 V, avoiding offset errors in precision 16-bit measurement circuits. |
| Telecom DC Power Input Stage | Consumer Appliance Motor Drive Protection |
|
Use Scenario: Guards primary-side 48 V DC input of PoE-powered network switches against lightning-induced surges on building wiring. IC Role / Device Role / Timing Role: First-line transient suppressor upstream of fuse and filter inboard of the connector, operating in unidirectional mode. Use Value: Withstands 400 W pulses without degradation, ensuring >100,000 surge cycles per Telcordia GR-1089-CORE Annex G requirements. |
Use Scenario: Protects H-bridge gate drivers from back-EMF spikes generated by brushed DC motors in smart home appliances. IC Role / Device Role / Timing Role: Placed across motor terminals or supply rails to clamp inductive kickback during PWM commutation. Use Value: Fast <1 ns response prevents shoot-through in N-channel MOSFETs by limiting VDS overshoot to safe levels below 100 V rating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ78A-M3/5A | Halogen-free, RoHS-compliant variant with identical electrical specs and SMA package | No functional difference; selected where halogen-free BOM compliance is mandated (e.g., EU medical devices) | Direct material substitution when halogen-free certification is required; same footprint and thermal performance |
| SMAJ78AHE3_A/I | AEC-Q101 qualified version with enhanced reliability testing (HTOL, TCT, UHAST); otherwise identical VBR, VC, PPPM | Required for automotive safety-critical modules (ASIL-B compatible designs) where qualification evidence is mandatory | Preferred for Tier 1 automotive programs needing documented AEC-Q101 data; not drop-in without qualification review |
Compared with SMAJ78A-E3/5A, the M3/5A offers halogen-free compliance without electrical trade-offs, while the HE3_A/I adds AEC-Q101 validation for automotive use - neither is pin-compatible in qualification context, but all share identical SMA footprint, polarity marking, and surge ratings.
Availability
SMAJ78A-E3/5A is available at Aetrix Electronics and suitable for automotive electronics, industrial sensor interfaces, telecom power inputs, and consumer appliance motor drives requiring stable component supply across long production lifecycles.
Supply support for SMAJ78A-E3/5A 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, and protection devices with emphasis on reliability, power efficiency, and automotive-grade qualification.
The SMAJ series was developed for high-energy transient suppression in harsh environments, targeting 12 V/24 V/48 V systems where compact size, fast response, and repeatable clamping are essential - especially in automotive, industrial, and telecom infrastructure.
FAQ
What is the clamping voltage of SMAJ78A-E3/5A at its rated peak pulse current?
The SMAJ78A-E3/5A clamps to a maximum of 126 V at its specified peak pulse current of 3.2 A under the standard 10/1000 μs waveform. This value is measured per Figure 1 and Table 1 in Vishay Document 88390, and defines the upper voltage limit imposed on protected circuitry during surge events. The clamping voltage remains stable across temperature due to its low 0.057 %/°C VBR temperature coefficient.
Is SMAJ78A-E3/5A suitable for automotive applications?
SMAJ78A-E3/5A itself is not AEC-Q101 qualified, but it belongs to the SMAJ family for which Vishay offers AEC-Q101 variants (e.g., SMAJ78AHE3_A/I). For non-safety-critical automotive subsystems like body control modules or infotainment power rails, SMAJ78A-E3/5A is widely deployed - however, formal qualification requires the HE3 or HM3 suffix versions with full test reports. Its 150 °C TJ max and robust surge rating support under-hood use cases.
What is the meaning of the "E3/5A" suffix in SMAJ78A-E3/5A?
The "E3" denotes RoHS-compliant, commercial-grade construction with matte tin-plated leads, while "/5A" specifies the packaging format: 13-inch diameter plastic tape and reel containing 7500 units. This differs from "/61", which indicates 7-inch reel with 1800 units. Both formats maintain identical electrical and thermal specifications - the suffix solely identifies environmental compliance and logistics configuration for SMAJ78A-E3/5A.
How does SMAJ78A-E3/5A differ from bidirectional SMAJ78CA variants?
SMAJ78A-E3/5A is unidirectional, featuring a cathode band and conducting only in forward bias during surge events, whereas SMAJ78CA is bidirectional with symmetrical clamping in both polarities and no polarity marking. Electrically, SMAJ78A-E3/5A has VWM = 78 V and VBR = 86.7–95.8 V, while SMAJ78CA shares the same VWM but exhibits matched breakdown in both directions. Use SMAJ78A-E3/5A for DC power line protection; choose SMAJ78CA for AC-coupled or floating signal lines.
What PCB layout guidance applies to SMAJ78A-E3/5A for optimal thermal and surge performance?
For optimal performance, mount SMAJ78A-E3/5A on minimum 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal as specified in Vishay Document 88390. This pad area supports its 400 W peak pulse rating and limits junction temperature rise via RθJA = 120 °C/W. Avoid narrow traces between the device and protected node - keep interconnect inductance low to preserve sub-nanosecond response. Thermal vias under pads further improve heat dissipation in high-duty-cycle applications.
SMAJ78A-E3/5A 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-E3/5A FAQ
1.How can I place an order for SMAJ78A-E3/5A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ78A-E3/5A 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-E3/5A reliable?
The price and inventory of SMAJ78A-E3/5A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ78A-E3/5A is usually 5 days.
3.What payment methods are accepted for SMAJ78A-E3/5A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ78A-E3/5A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ78A-E3/5A?
SMAJ78A-E3/5A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ78A-E3/5A 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-E3/5A?
For technical support, including SMAJ78A-E3/5A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ78A-E3/5A requirements.
6.How does Aetrix verify that SMAJ78A-E3/5A is sourced from the original manufacturer or authorized distributors?
All SMAJ78A-E3/5A 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-E3/5A meets industry standards.
7.What is the process for return or replacement of SMAJ78A-E3/5A?
All SMAJ78A-E3/5A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ78A-E3/5A, 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-E3/5A part is unused and in its original packaging.
Return procedure for SMAJ78A-E3/5A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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