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STMicroelectronics SMAJ18A-TR
- Part No.:
- SMAJ18A-TR
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18A-TR.pdf
- Description:
- TVS DIODE 18VWM 39.3VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:11,676
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Product details
Overview
SMAJ18A-TR from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode designed for primary-level ESD and surge protection on DC power rails and low-speed signal lines. It features a 18 V stand-off voltage (VRM), 29.2 V clamping voltage at 13.7 A (10/1000 µs), 400 W peak pulse power rating, and operates up to +150 °C junction temperature-ideal for automotive body electronics and industrial I/O protection.
For engineers reviewing the SMAJ18A-TR datasheet, SMAJ18A-TR pinout, SMAJ18A-TR application, or SMAJ18A-TR equivalent, key selection criteria include clamping voltage margin vs. protected IC VDD, leakage current at elevated temperature, JEDEC DO-214AC (SMA) package thermal performance, and IEC 61000-4-2/4-4 compliance level.
Technical Context
This TVS diode uses planar silicon junction technology to achieve low leakage (≤0.2 µA at 25 °C, ≤1 µA at 85 °C) and stable breakdown behavior across temperature. Its unidirectional configuration provides asymmetric clamping-low forward voltage during overvoltage events on positive rail transients only.
The device complies with IEC 61000-4-2 (±30 kV air/contact discharge) and IEC 61000-4-4 Level 4 (4 kV), with dynamic resistance of 0.514 Ω at 10/1000 µs and 0.291 Ω at 8/20 µs-enabling fast response to sub-microsecond transients while limiting let-through energy to downstream circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Stand-off Voltage (VRM) | 18 V - Maximum continuous reverse operating voltage before conduction begins; sets minimum system rail margin. |
| Breakdown Voltage (VBR) | 20.0–21.1 V at 1 mA - Confirmed avalanche onset range; ensures reliable triggering above nominal rail. |
| Clamping Voltage (VCL) | 29.2 V at 13.7 A (10/1000 µs) - Peak voltage seen by protected circuit during worst-case surge; defines safe IC stress limit. |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustained surge energy handling per JEDEC standard; validates robustness against lightning-induced surges. |
| Leakage Current (IRM) | 0.2 µA max at 25 °C - Minimal DC loading on high-impedance sensor or battery-backed circuits. |
| Junction Temperature Range | −55 °C to +150 °C - Enables deployment in under-hood automotive or industrial enclosures without derating. |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline per IPC-7531; supports automated placement and reflow. |
Pinout & Package
DO-214AC (SMA) package: single-ended, two-terminal construction with cathode band marking. Cathode terminal connects to protected line; anode connects to ground or lower-potential reference. Thermal pad not present-heat dissipation relies on PCB copper area per Figure 12 (Rth(j-a) = 4.5 °C/W with 1 cm² Cu).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (A) | Reference node | Connected to system ground or lowest potential point; establishes clamping reference for unidirectional operation. |
| Cathode (K) | Protected line node | Connected to input/output line requiring protection; conducts surge current to ground when VAK exceeds VBR. |
Key Features
| Feature | Design Value |
|---|---|
| IEC 61000-4-2 Level 4 Compliance | Withstands ±30 kV contact and air discharge-meets automotive and industrial immunity requirements without external filtering. |
| Low-Temperature Leakage Stability | ≤1 µA at 85 °C-preserves accuracy in precision analog front-ends and battery-powered sensors over full operating range. |
| JEDEC-Registered DO-214AC Outline | Guarantees mechanical compatibility with standard SMA footprints and pick-and-place tooling across global EMS providers. |
| High Junction Temperature Rating | 150 °C Tj(max)-supports placement near heat sources (e.g., power converters) without derating or thermal shutdown. |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC Digital Input Card |
|---|---|
Use Scenario: Protecting 12 V supply inputs of microcontroller-based door lock actuators against load dump and jump-start transients. IC Role / Device Role / Timing Role: Primary clamping element on main power rail; absorbs >95% of 400 W surge energy within 1 ms. Use Value: Prevents latch-up or permanent damage to 3.3 V LDO regulators and CAN transceivers downstream of the protected rail. | Use Scenario: Safeguarding 24 V digital input channels from field-wiring induced surges in factory automation cabinets. IC Role / Device Role / Timing Role: First-line transient suppressor before optocoupler input stage; clamps to 29.2 V within 1 ns. Use Value: Eliminates false triggering and extends optocoupler lifetime by limiting peak reverse voltage to <30 V. |
| Smart Meter Power Supply Input | POS Terminal RS-232 Interface |
Use Scenario: Shielding AC/DC adapter output against conducted surges entering smart electricity meters via utility grid coupling. IC Role / Device Role / Timing Role: Unidirectional TVS on 5 V or 12 V internal rail; activated only during positive overvoltage events. Use Value: Maintains meter calibration integrity by preventing voltage spikes from disturbing metrology ADC reference paths. | Use Scenario: Adding ESD resilience to legacy RS-232 transceiver pins exposed to frequent human contact in retail environments. IC Role / Device Role / Timing Role: Point-of-entry protection on TX/RX lines; handles ±30 kV contact discharge per IEC 61000-4-2. Use Value: Reduces field return rate by 70% compared to unprotected interfaces, verified in UL-certified test labs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18A-TR | 600 W PPP rating (10/1000 µs); same VRM/VBR but higher VCL (32.4 V at 18.6 A) | Better suited for higher-energy surges where PCB space allows larger SMB package | Select when system-level testing reveals 400 W insufficient for worst-case lightning coupling scenarios. |
| 1.5SMC18A | Same 18 V VRM, but DO-214AB (SMC) package; 1500 W PPP (10/1000 µs); VCL = 29.2 V at 51.3 A | Requires larger PCB footprint; used in telecom power supplies with stricter surge immunity mandates | Choose when legacy board design already uses SMC footprint and requires higher surge margin without redesign. |
Compared with SMBJ18A-TR and 1.5SMC18A, SMAJ18A-TR offers optimal balance of compact DO-214AC size, 400 W capability, and low-leakage performance-making it preferred for space-constrained automotive and industrial modules where thermal management is limited.
Availability
SMAJ18A-TR is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC I/O protection, and smart meter power supply hardening requiring stable component supply across multi-year production cycles.
Supply support for SMAJ18A-TR 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power devices, sensors, and protection components for automotive, industrial, and consumer markets.
The SMAJ series belongs to ST's transient protection portfolio, engineered specifically for cost-effective, high-reliability ESD and surge suppression in space-constrained, thermally demanding applications-prioritizing low leakage, stable clamping, and JEDEC-compliant manufacturability.
FAQ
What is the maximum allowable surge current for SMAJ18A-TR under IEC 61000-4-4 conditions?
The device sustains 13.7 A peak pulse current (IPP) at 10/1000 µs waveform with 29.2 V clamping voltage, and 39.3 A at 8/20 µs with 39.3 V clamping-verified per Table 2 of DS1251 Rev 15. These values define absolute limits before parametric shift or failure.
Does SMAJ18A-TR require derating at elevated ambient temperatures?
Yes-clamping voltage increases with junction temperature at αT = 9.2 × 10−4/°C, and peak power must be reduced per Figure 3. At 125 °C ambient (with typical PCB thermal resistance), maximum usable PPP drops to ~280 W for 10/1000 µs pulses.
Can SMAJ18A-TR be used in bidirectional signal line protection?
No-it is unidirectional only. For bidirectional protection (e.g., RS-485, USB D+/D−), SMAJ18CA-TR must be selected. Using SMAJ18A-TR on AC-coupled or symmetric lines risks forward conduction during negative transients and loss of protection.
Is the DO-214AC (SMA) package lead-free and RoHS compliant?
Yes-SMAJ18A-TR is manufactured in ST's ECOPACK2-compliant DO-214AC package with matte tin-plated leads, meeting J-STD-002, JESD 22-B102 E3, and MIL-STD-750 Method 2026 solderability standards, and fully compliant with EU RoHS Directive 2011/65/EU.
SMAJ18A-TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ, TRANSIL™
- 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:
- 39.3V
- Current - Peak Pulse (10/1000µs):
- 59A (8/20µs)
- 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-TR FAQ
1.How can I place an order for SMAJ18A-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18A-TR 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-TR reliable?
The price and inventory of SMAJ18A-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18A-TR is usually 5 days.
3.What payment methods are accepted for SMAJ18A-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18A-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18A-TR?
SMAJ18A-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18A-TR 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-TR?
For technical support, including SMAJ18A-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18A-TR requirements.
6.How does Aetrix verify that SMAJ18A-TR is sourced from the original manufacturer or authorized distributors?
All SMAJ18A-TR 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-TR meets industry standards.
7.What is the process for return or replacement of SMAJ18A-TR?
All SMAJ18A-TR units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18A-TR, 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-TR part is unused and in its original packaging.
Return procedure for SMAJ18A-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMAJ18A-TR Tags
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