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Vishay General Semiconductor - Diodes Division SMAJ18A-E3/5A
- Part No.:
- SMAJ18A-E3/5A
- Manufacturer:
- Vishay General Semiconductor - Diodes Division
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18A-E3/5A.pdf
- Description:
- TVS DIODE 18VWM 29.2VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:5,415
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Product details
Overview
SMAJ18A-E3/5A from Vishay General Semiconductor is a unidirectional transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for robust overvoltage protection of sensitive electronics. It features a 18 V stand-off voltage (VWM), 20.0–22.1 V breakdown voltage (VBR) at 1 mA, 29.2 V maximum clamping voltage (VC) at 13.7 A peak pulse current (IPPM), and 400 W peak pulse power (10/1000 μs waveform), commonly deployed on DC power rails and I/O lines in automotive ECUs and industrial sensor interfaces.
For engineers reviewing the SMAJ18A-E3/5A datasheet, SMAJ18A-E3/5A pinout, SMAJ18A-E3/5A application, or SMAJ18A-E3/5A equivalent, key selection criteria include clamping performance under 13.7 A surge, unidirectional polarity with cathode band marking, RoHS-compliant matte tin plating, and compatibility with automated SMT placement on 0.2" × 0.2" copper pads.
Technical Context
This TVS diode operates as a voltage-clamped shunt protector: when reverse voltage exceeds VBR (20.0–22.1 V), it avalanches to limit transient energy by diverting surge current away from downstream circuitry. Its low incremental surge resistance and fast response time (<1 ns) ensure effective suppression of ESD, lightning-induced surges, and inductive switching transients.
The device is rated for 400 W peak pulse power (10/1000 μs) up to 78 V; above that threshold, derated to 300 W. Thermal resistance is 120 °C/W junction-to-ambient (RθJA) and 30 °C/W junction-to-lead (RθJL), supporting reliable operation within -55 °C to +150 °C junction temperature range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 18 V - Maximum continuous reverse operating voltage before conduction begins; defines safe DC bias margin. |
| VBR (min/max) | 20.0 V / 22.1 V at 1 mA - Breakdown onset range; ensures predictable clamping initiation across process variation. |
| VC @ IPPM | 29.2 V at 13.7 A - Clamped voltage during full-rated 10/1000 μs surge; determines protected circuit's maximum transient exposure. |
| PPPM | 400 W (≤78 V), 300 W (>78 V) - Peak surge energy handling capability; defines survivability against standardized lightning/inductive transients. |
| ID @ VWM | 1.0 μA - Reverse leakage at stand-off voltage; negligible power loss and signal integrity impact in standby. |
| TJ max. | +150 °C - Maximum junction temperature; supports under-hood automotive and high-ambient industrial use. |
| Package | SMA (DO-214AC) - Surface-mount outline with 0.208" length, 0.157" width, and 0.090" height; compatible with standard SMT reflow profiles (MSL Level 1, 260 °C peak). |
Pinout & Package
Package: SMA (DO-214AC), molded plastic case with matte tin-plated leads; polarity indicated by cathode band on unidirectional devices.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward current entry / reverse surge return path | Connected to lower-potential side (e.g., GND or return rail); completes clamping loop during transient events. |
| Cathode | Reverse-biased terminal / surge current sink | Marked with band; connected to protected line (e.g., 12 V supply or signal input); conducts avalanche current during overvoltage. |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power (10/1000 μs) | Enables single-device protection against IEC 61000-4-5 Level 4 (4 kV surge) on 12 V systems without external series impedance. |
| 29.2 V clamping voltage at 13.7 A | Limits voltage stress on downstream 3.3 V/5 V logic or MOSFET gate drivers during worst-case surge conditions. |
| Low 1.0 μA leakage at 18 V | Prevents measurable quiescent current drain in battery-powered or always-on circuits (e.g., automotive body control modules). |
| AEC-Q101 qualification option (HE3/HM3 suffix) | Validates reliability for automotive applications including engine control, ADAS sensors, and infotainment power supplies. |
| MSL Level 1 moisture sensitivity | Allows unlimited floor life and standard reflow without baking; simplifies manufacturing for high-volume SMT lines. |
Applications
| Automotive Power Rail Protection | Industrial Sensor Interface Protection |
|---|---|
|
Use Scenario: 12 V battery-supplied microcontroller power input in engine control unit exposed to load dump and alternator ripple. IC Role / Device Role / Timing Role: Unidirectional shunt TVS diode clamping positive transients on VCC rail. Use Value: Limits voltage excursion to ≤29.2 V during 13.7 A surge, preventing latch-up or oxide breakdown in 3.3 V MCU core. |
Use Scenario: 4–20 mA current-loop transmitter output connected to PLC analog input in factory automation. IC Role / Device Role / Timing Role: Bidirectional-capable unidirectional TVS placed across loop terminals to absorb field-wiring induced surges. Use Value: Withstands 400 W transients without degradation, maintaining loop accuracy and avoiding false trip in safety-critical monitoring. |
| Consumer USB Port ESD Protection | Telecom DC Feeder Line Surge Suppression |
|
Use Scenario: VBUS line of USB 2.0 port on smart speaker subjected to human-body-model (HBM) ESD events. IC Role / Device Role / Timing Role: Primary shunt clamp on 5 V supply rail upstream of USB controller IC. Use Value: Sub-1 ns response and 29.2 V clamping prevent damage to USB PHY transceivers rated for ≤6 V absolute maximum. |
Use Scenario: -48 V DC power feed to remote radio head in cellular base station exposed to lightning-induced common-mode surges. IC Role / Device Role / Timing Role: Unidirectional TVS on negative rail referenced to chassis ground to clamp negative-going transients. Use Value: 400 W rating and 150 °C TJ max enable sustained operation in outdoor enclosures with minimal thermal derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ18A-M3/5A | Halogen-free, RoHS-compliant variant with identical electrical specs and SMA package. | No functional difference; selected where halogen-free compliance is mandated (e.g., EU public infrastructure projects). | Direct material substitution if halogen-free requirement applies; same layout and thermal profile. |
| SMAJ18CA-E3/5A | Bidirectional version: symmetric VBR (20.0–22.1 V) in both directions; same VWM, VC, and PPPM ratings. | Required for AC-coupled or floating signal lines (e.g., RS-485, CAN bus) where polarity reversal occurs. | Choose only when bidirectional clamping is needed; not interchangeable in unidirectional DC rail applications due to leakage path. |
Compared with SMAJ18A-E3/5A, the M3 variant offers identical protection performance with halogen-free construction, while the SMAJ18CA-E3/5A enables symmetrical clamping for AC or differential signals-neither is pin-compatible without verifying circuit polarity and grounding scheme.
Availability
SMAJ18A-E3/5A is available at Aetrix Electronics and suitable for automotive electronics, industrial sensor interfaces, and consumer power supply protection requiring stable component supply and long-term manufacturability.
Supply support for SMAJ18A-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, MOSFETs, and protection devices with emphasis on reliability, efficiency, and application-specific optimization.
The SMAJ series is engineered for high-energy transient suppression in harsh environments, targeting automotive, industrial, and telecom applications where robustness against ESD, lightning, and inductive switching is critical.
FAQ
What is the clamping voltage of SMAJ18A-E3/5A at its rated peak pulse current?
The SMAJ18A-E3/5A exhibits a maximum clamping voltage (VC) of 29.2 V when subjected to its rated peak pulse current (IPPM) of 13.7 A under the standard 10/1000 μs waveform. This value is measured per JEDEC test conditions and defines the upper voltage limit imposed on protected circuitry during surge events. The SMAJ18A-E3/5A maintains this clamping performance across its qualified operating temperature range.
Is SMAJ18A-E3/5A suitable for automotive applications?
SMAJ18A-E3/5A is RoHS-compliant and qualified to AEC-Q101 when ordered with HE3 or HM3 suffixes; the base SMAJ18A-E3/5A is commercial-grade but shares identical electrical and thermal specifications. For automotive use, specify SMAJ18AHE3/5A to ensure qualification. The SMAJ18A-E3/5A's 150 °C TJ max and 400 W surge rating meet requirements for under-hood and body-control module protection.
How does the SMAJ18A-E3/5A differ from SMAJ18CA-E3/5A?
The SMAJ18A-E3/5A is unidirectional, with a cathode band indicating polarity and clamping only in reverse bias; the SMAJ18CA-E3/5A is bidirectional, offering symmetric clamping in both directions with no polarity marking. Both share identical VWM (18 V), VBR (20.0–22.1 V), VC (29.2 V), and PPPM (400 W), but SMAJ18CA-E3/5A must be used where AC signals or reversible voltage transients occur.
What is the thermal resistance of SMAJ18A-E3/5A and how does it affect PCB layout?
SMAJ18A-E3/5A has a typical junction-to-ambient thermal resistance (RθJA) of 120 °C/W and junction-to-lead (RθJL) of 30 °C/W. To maintain reliability under repeated surges, Vishay specifies mounting on 0.2" × 0.2" (5.0 mm × 5.0 mm) copper pads per terminal. Reducing pad size increases thermal impedance, risking junction overheating; the SMAJ18A-E3/5A's performance assumes this minimum copper area.
Does SMAJ18A-E3/5A require additional series impedance for effective protection?
No, SMAJ18A-E3/5A is designed for direct parallel connection to protected lines and does not require external series impedance for basic clamping function. However, in high-energy applications (e.g., IEC 61000-4-5), a current-limiting resistor or PTC may be added upstream to reduce peak dissipation in the SMAJ18A-E3/5A and extend its lifetime under repetitive surges. The SMAJ18A-E3/5A itself provides immediate low-impedance shunting once VBR is exceeded.
SMAJ18A-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):
- 18V
- Voltage - Breakdown (Min):
- 20V
- Voltage - Clamping (Max) @ Ipp:
- 29.2V
- Current - Peak Pulse (10/1000µs):
- 13.7A
- 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)
SMAJ18A-E3/5A FAQ
1.How can I place an order for SMAJ18A-E3/5A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18A-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 SMAJ18A-E3/5A reliable?
The price and inventory of SMAJ18A-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 SMAJ18A-E3/5A is usually 5 days.
3.What payment methods are accepted for SMAJ18A-E3/5A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18A-E3/5A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18A-E3/5A?
SMAJ18A-E3/5A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18A-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 SMAJ18A-E3/5A?
For technical support, including SMAJ18A-E3/5A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18A-E3/5A requirements.
6.How does Aetrix verify that SMAJ18A-E3/5A is sourced from the original manufacturer or authorized distributors?
All SMAJ18A-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 SMAJ18A-E3/5A meets industry standards.
7.What is the process for return or replacement of SMAJ18A-E3/5A?
All SMAJ18A-E3/5A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18A-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 SMAJ18A-E3/5A part is unused and in its original packaging.
Return procedure for SMAJ18A-E3/5A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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