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STMicroelectronics SMAJ18CA-TR
- Part No.:
- SMAJ18CA-TR
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ18CA-TR.pdf
- Description:
- TVS DIODE 18VWM 39.3VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:4,643
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Product details
Overview
SMAJ18CA-TR from STMicroelectronics is a bidirectional transient voltage suppression (TVS) diode designed for ESD and surge protection in DC power rails and signal lines. It features a 18 V standoff voltage (VRM), 29.2 V clamping voltage at 13.7 A (10/1000 µs), 400 W peak pulse power, and operates up to +150 °C junction temperature - deployed in industrial power supplies and automotive body control modules.
For engineers reviewing the SMAJ18CA-TR datasheet, SMAJ18CA-TR pinout, SMAJ18CA-TR application, or SMAJ18CA-TR equivalent, key selection criteria include bidirectional clamping behavior, low leakage (<1 µA at 85 °C), JEDEC DO-214AC (SMA) package compatibility, and IEC 61000-4-2/4-4 compliance for system-level immunity validation.
Technical Context
This TVS diode uses planar silicon junction technology to achieve stable breakdown characteristics and low dynamic resistance (0.514 Ω at 25 °C). Its bidirectional configuration enables symmetric clamping on AC-coupled or floating lines without polarity dependency.
The device meets IEC 61000-4-2 Level 4 (±30 kV contact/air discharge) and IEC 61000-4-4 Level 4 (4 kV), with thermal design validated for FR4 PCBs using IPC-7531-compliant footprint and 70 µm copper thickness.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standoff Voltage (VRM) | 18 V - Maximum continuous reverse operating voltage before significant leakage or conduction begins. |
| Breakdown Voltage (VBR) | 20.0–21.1 V at 1 mA - Confirmed minimum/typical avalanche onset threshold under DC test conditions. |
| Clamping Voltage (VCL) | 29.2 V at 13.7 A (10/1000 µs) - Peak voltage seen by protected circuit during standardized surge event. |
| Peak Pulse Power (PPP) | 400 W (10/1000 µs) - Sustained energy-handling capability for common lightning-induced transients. |
| Leakage Current (IRM) | 0.2 µA at 25 °C, 1 µA at 85 °C - Ensures minimal loading on high-impedance sensor or reference circuits. |
| Junction Temperature Range | −55 °C to +150 °C - Supports operation in under-hood automotive or industrial ambient environments. |
| Package | DO-214AC (SMA) - Surface-mount outline compliant with IPC-7531 footprint and JEDEC registration. |
Pinout & Package
Package: DO-214AC (SMA), single-axis symmetrical case with cathode band marking; dimensions per JEDEC MS-013 (EIAJ ED-7330A), 2.25–2.90 mm width, 4.80–5.35 mm length, 1.90–2.45 mm height.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (unmarked end) | Transient current sink (bidirectional) | Conducts during negative surges; forms symmetrical clamping path with cathode. |
| Cathode (banded end) | Transient current sink (bidirectional) | Conducts during positive surges; identical clamping performance as anode due to bidirectional structure. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional clamping | Enables protection of AC signals or floating buses without polarity constraints or external diode pairing. |
| Low dynamic resistance | 0.514 Ω at 25 °C - Minimizes voltage overshoot during fast-rising transients (e.g., ESD). |
| High-temperature reliability | Rated for 150 °C junction operation - Maintains clamping stability in thermally stressed PCB layouts. |
| IEC 61000-4-2/4-4 certified | Validated to ±30 kV air/contact discharge and 4 kV electrical fast transient burst - Reduces need for additional system-level testing. |
| Planar junction construction | Delivers consistent VBR tolerance and low leakage across temperature - Critical for precision analog front-ends. |
Applications
| Industrial PLC I/O Protection | Automotive Body Control Module |
|---|---|
Use Scenario: Protecting 24 V digital input channels against induced surges from relay coil flyback or nearby motor switching. IC Role / Device Role / Timing Role: Standoff-clamp TVS placed directly at connector entry point, shunting transient energy to ground before reaching MCU GPIO. Use Value: Limits voltage to ≤29.2 V during 13.7 A surge, preventing latch-up or permanent damage to 3.3 V/5 V logic interfaces. | Use Scenario: Safeguarding LIN bus transceivers and sensor supply lines in door module assemblies exposed to load dump and ESD. IC Role / Device Role / Timing Role: Bidirectional clamping element on 12 V rail and LIN signal line, absorbing both positive and negative transients. Use Value: Withstands 30 kV contact discharge per IEC 61000-4-2 and maintains <1 µA leakage at 85 °C cabin temperature. |
| Medical Patient Monitor Ports | Smart Energy Meter Communication Interfaces |
Use Scenario: Shielding isolated RS-232/RS-485 ports connected to external diagnostic equipment subject to accidental ESD events. IC Role / Device Role / Timing Role: Secondary protection stage after primary gas discharge tube, providing low-clamp, fast-response final barrier. Use Value: Clamps within nanoseconds to ≤29.2 V, preserving signal integrity and meeting IEC 60601-1-2 immunity requirements. | Use Scenario: Protecting HPLC/PLC communication lines (e.g., M-Bus, RF mesh) in utility meters installed in outdoor enclosures. IC Role / Device Role / Timing Role: Primary surge suppressor on 24 V auxiliary supply and data pair, mounted adjacent to connector per IEC 61000-4-4 layout guidelines. Use Value: Handles 4 kV EFT bursts while maintaining <0.2 µA leakage at 25 °C - avoids false triggering in low-power wake-up circuits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18CA-TR | Higher 600 W (10/1000 µs) rating; larger SMB package (DO-214AA); 32.4 V clamping at 12.3 A. | Better suited for higher-energy surges but requires more PCB area and has higher thermal resistance. | Select when surge threat exceeds 400 W and board space permits larger footprint. |
| 1.5SMC18CA | Same 18 V VRM, 32.4 V VCL at 12.3 A, but 1500 W rating; DO-214AB (SMC) package; higher capacitance (~1000 pF). | Higher clamping voltage and junction capacitance limit use in high-speed data lines. | Prefer for robust power rail protection where speed or capacitance is not critical. |
Compared with SMBJ18CA-TR and 1.5SMC18CA, SMAJ18CA-TR offers optimal balance of compact DO-214AC size, low clamping (29.2 V), and sufficient 400 W surge handling for space-constrained industrial and automotive signal-line protection.
Availability
SMAJ18CA-TR is available at Aetrix Electronics and suitable for industrial PLC I/O protection, automotive body control modules, medical patient monitor ports, and smart energy meter communication interfaces requiring stable component supply and full traceability.
Supply support for SMAJ18CA-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, delivering innovative solutions across automotive, industrial, power, and embedded markets.
The SMAJ series belongs to ST's transient protection portfolio, engineered specifically for high-reliability, low-leakage ESD/surge suppression in space-constrained, thermally demanding applications.
FAQ
What is the difference between SMAJ18CA-TR and SMAJ18A-TR?
SMAJ18CA-TR is bidirectional (symmetrical clamping for both polarities), while SMAJ18A-TR is unidirectional (clamps only positive transients, with cathode-to-ground orientation). The CA version eliminates polarity concerns in AC-coupled or floating systems and supports dual-rail protection without discrete diode pairing.
Does SMAJ18CA-TR require a heatsink for 400 W surge dissipation?
No heatsink is required: the 400 W rating applies to a single 10/1000 µs pulse with Tj initial = 25 °C. Thermal analysis shows junction temperature rise remains within 150 °C limit on standard FR4 with IPC-7531 footprint and 70 µm copper, assuming proper land pattern and reflow profile per J-STD-020 MSL level 1.
Can SMAJ18CA-TR be used on USB or Ethernet data lines?
Not recommended for high-speed data lines: its typical junction capacitance is ~300–500 pF (per Figure 8), which would severely degrade signal integrity above ~1 MHz. It is intended for DC power rails and low-frequency control signals (e.g., LIN, CAN standby lines, digital I/O), not USB 2.0/3.0 or 100BASE-TX.
How does temperature affect clamping voltage in SMAJ18CA-TR?
VCL increases with junction temperature at 9.2 × 10⁻⁴/°C (αT = 9.2 × 10⁻⁴/°C). At 125 °C, VCL rises ~0.92 V above its 25 °C value (29.2 V → ~30.1 V), verified by the formula VCL(Tj) = VCL(25°C) × [1 + αT × (Tj − 25)]. This drift is factored into system margin calculations for high-ambient designs.
SMAJ18CA-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:
- -
- Bidirectional Channels:
- 1
- 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)
SMAJ18CA-TR FAQ
1.How can I place an order for SMAJ18CA-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ18CA-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 SMAJ18CA-TR reliable?
The price and inventory of SMAJ18CA-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ18CA-TR is usually 5 days.
3.What payment methods are accepted for SMAJ18CA-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ18CA-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ18CA-TR?
SMAJ18CA-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ18CA-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 SMAJ18CA-TR?
For technical support, including SMAJ18CA-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ18CA-TR requirements.
6.How does Aetrix verify that SMAJ18CA-TR is sourced from the original manufacturer or authorized distributors?
All SMAJ18CA-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 SMAJ18CA-TR meets industry standards.
7.What is the process for return or replacement of SMAJ18CA-TR?
All SMAJ18CA-TR units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ18CA-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 SMAJ18CA-TR part is unused and in its original packaging.
Return procedure for SMAJ18CA-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMAJ18CA-TR Tags
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