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STMicroelectronics SMBJ18CA-TR
- Part No.:
- SMBJ18CA-TR
- Manufacturer:
- STMicroelectronics
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SMBJ18CA-TR.pdf
- Description:
- TVS DIODE 18VWM 29.2VC SMB
- Quantity:
- Payment:
- Shipping:
Inventory:11,667
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Product details
Overview
SMBJ18CA-TR from STMicroelectronics is a bidirectional transient voltage suppression (TVS) diode in SMB package, designed to protect sensitive signal and power lines against ESD (IEC 61000-4-2 ±30 kV air/contact), EFT (IEC 61000-4-4 Level 4, 4 kV), and lightning-induced surges. It features a 18 V standoff voltage (VRM), 29.2 V clamping voltage at 21.5 A (10/1000 µs), 600 W peak pulse power, 0.2 µA max leakage at 25 °C, and operates up to 150 °C junction temperature - deployed in industrial PLC I/O modules, automotive body control units, and PoE-powered Ethernet interfaces.
For engineers reviewing the SMBJ18CA-TR datasheet, SMBJ18CA-TR pinout, SMBJ18CA-TR application, or SMBJ18CA-TR equivalent, key selection criteria include bidirectional clamping symmetry, low dynamic resistance (0.328 Ω), high-temperature leakage stability, UL497B recognition for isolated loop protection, and compatibility with IPC7531 footprint and JEDEC SMB outline.
Technical Context
This TVS diode uses planar silicon junction technology to achieve precise breakdown voltage control and stable clamping under repetitive surge stress. Its bidirectional architecture ensures symmetrical protection for AC-coupled or floating signal paths without polarity dependency.
Clamping performance is defined by VCL = 29.2 V at IPP = 21.5 A (10/1000 µs), with dynamic resistance RD = 0.328 Ω enabling rapid voltage limiting during fast transients. Temperature coefficients (αT = 9.2 × 10⁻⁴ /°C) allow accurate VBR and VCL derating across –55 °C to +150 °C operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standoff Voltage (VRM) | 18 V - Maximum continuous reverse working voltage before significant leakage; defines minimum system operating margin. |
| Breakdown Voltage (VBR min) | 20.0 V at 1 mA - Guaranteed avalanche initiation threshold; ensures reliable triggering above normal signal swing. |
| Clamping Voltage (VCL) | 29.2 V at 21.5 A (10/1000 µs) - Peak voltage seen by protected circuit during worst-case surge; determines IC survivability. |
| Peak Pulse Power (PPP) | 600 W (10/1000 µs) - Sustained surge energy handling at 25 °C; derates to 350 W at 150 °C junction temp. |
| Leakage Current (IRM) | 0.2 µA max at 18 V and 25 °C - Negligible loading on high-impedance sensor or reference circuits. |
| Junction Temp Range (Tj) | –55 °C to +150 °C - Enables deployment in under-hood automotive or industrial motor drive environments. |
| ESD Rating | ±30 kV contact & air discharge (IEC 61000-4-2) - Exceeds Level 4 immunity requirements for user-accessible ports. |
Pinout & Package
Package: SMB (DO-214AA), surface-mount, JEDEC registered outline, matte tin-plated leads, IPC7531-compliant footprint. Dimensions: 3.30–3.95 mm (L) × 5.10–5.60 mm (W) × 1.90–2.45 mm (H).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Marked Band) | Anode connection for unidirectional variant; symmetric terminal for bidirectional operation | In SMBJ18CA-TR (bidirectional), both terminals are functionally identical - no polarity sensitivity; enables placement on AC or differential lines without orientation check. |
| Anode (Opposite Band) | Second terminal of bidirectional junction | Provides matched clamping in both directions; measured VBR and VCL values are identical for positive and negative surges. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional clamping symmetry | Identical VBR (20.0/21.1 V) and VCL (29.2 V) for ± polarity - eliminates need for polarity-aware layout in RS-485, CAN, or audio lines. |
| Low dynamic resistance | 0.328 Ω - minimizes voltage overshoot during fast-rising transients (<1 ns rise time), critical for protecting 3.3 V or 5 V logic inputs. |
| High-temperature leakage stability | 1 µA max at 85 °C and VRM - maintains signal integrity in thermally stressed enclosures without false triggering. |
| UL497B recognition | Agency file E136224 - certifies suitability as isolated loop circuit protector in telecom and industrial safety-critical systems. |
| Robust surge capability | 4 kW peak power (8/20 µs waveform) - handles high-current lightning-induced surges common in outdoor Ethernet or fieldbus wiring. |
Applications
| Industrial PLC Analog I/O | Automotive Body Control Module |
|---|---|
|
Use Scenario: Protecting 4–20 mA current-loop sensor inputs from ESD events during field wiring and maintenance. IC Role / Device Role / Timing Role: Bidirectional voltage clamp placed across input terminals to shunt transient energy before it reaches precision op-amps or ADC front-ends. Use Value: Prevents latch-up or permanent damage to 24-bit sigma-delta ADCs while maintaining <0.1 µA input bias error due to ultra-low IRM. |
Use Scenario: Safeguarding LIN bus transceivers and window lift motor drivers against load dump and jump-start transients. IC Role / Device Role / Timing Role: Secondary surge suppressor downstream of primary TVS, absorbing residual energy after main clamp activation. Use Value: Ensures >100,000-cycle reliability at 125 °C ambient by leveraging 150 °C Tj rating and stable RD over temperature. |
| IEEE 802.3af/at PoE PSE Interface | RS-485 Data Line Protection |
|
Use Scenario: Shielding Power Sourcing Equipment (PSE) controller pins from cable discharge events during hot-plug insertion. IC Role / Device Role / Timing Role: Fast-response TVS placed between VDD and GND on PSE detection/classification circuitry. Use Value: Clamps sub-100 ns ESD pulses to <30 V, preserving integrity of 10-bit DACs used for current sensing and classification accuracy. |
Use Scenario: Guarding full-duplex RS-485 transceivers connected to long outdoor runs exposed to induced lightning surges. IC Role / Device Role / Timing Role: Differential-mode clamp across A/B lines, with matched VCL ensuring common-mode rejection remains intact. Use Value: Delivers 4 kV EFT immunity (IEC 61000-4-4) and 4 kW 8/20 µs surge handling without degrading data rates up to 20 Mbps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient voltage suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ18A-TR | Unidirectional; VBR starts at 20.0 V only for positive polarity; no negative breakdown path. | Requires polarity-aware PCB layout; unsuitable for AC-coupled or floating differential buses like RS-485 or CAN. | Select only when protecting DC-biased single-ended signals (e.g., microcontroller GPIO) where reverse conduction must be blocked. |
| SMAJ18CA-TR | Same electrical specs but in smaller SMA package (DO-214AC); 400 W PPP (10/1000 µs) vs. 600 W; higher RD (0.42 Ω). | Lower power handling and thermal mass limit use in high-repetition surge environments (e.g., factory automation). | Choose for space-constrained designs where 400 W surge capacity suffices and board area is premium. |
Compared with SMBJ18A-TR, SMBJ18CA-TR enables polarity-agnostic protection with matched bidirectional clamping, while SMAJ18CA-TR trades 33% lower surge rating and reduced thermal robustness for 30% smaller footprint - making SMBJ18CA-TR optimal for high-reliability industrial and automotive signal line protection.
Availability
SMBJ18CA-TR is available at Aetrix Electronics and suitable for industrial PLC analog I/O, automotive body control modules, IEEE 802.3af/at PoE PSE interfaces, and RS-485 data line protection requiring stable component supply, UL497B compliance, and high-temperature operational continuity.
Supply support for SMBJ18CA-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, specializing in power management, analog, MEMS, and microcontrollers for industrial, automotive, and consumer markets.
SMBJxxCA series belongs to ST's high-reliability TVS portfolio, engineered specifically for robust transient suppression in harsh electromagnetic environments - targeting applications demanding UL recognition, extended temperature operation, and low-leakage signal integrity.
FAQ
What is the maximum clamping voltage for SMBJ18CA-TR under a 10/1000 µs surge?
The maximum clamping voltage is 29.2 V at 21.5 A for a 10/1000 µs waveform, measured at 25 °C ambient. This value increases with junction temperature at a coefficient of 9.2 × 10⁻⁴ /°C, reaching approximately 31.5 V at 125 °C junction temperature per the VCL(Tj) = VCL(25°C) × [1 + αT × (Tj − 25)] formula.
Does SMBJ18CA-TR meet UL497B requirements for isolated loop protection?
Yes - SMBJ18CA-TR is recognized to UL497B as an isolated loop circuit protector under agency file number E136224, covering both unidirectional and bidirectional variants. This certification validates its use in telecom interface circuits, industrial fieldbus isolators, and safety-rated signal conditioning modules.
How does SMBJ18CA-TR differ from SMBJ18A-TR in circuit implementation?
SMBJ18CA-TR is bidirectional, providing symmetrical clamping for both polarities, making it suitable for AC-coupled, differential, or floating lines like RS-485 or LIN. SMBJ18A-TR is unidirectional and conducts only in reverse bias, requiring correct orientation and blocking forward surges - limiting it to DC-biased single-ended nodes such as microcontroller I/O or sensor supply rails.
What is the recommended PCB footprint and thermal relief for SMBJ18CA-TR?
The device uses the JEDEC DO-214AA (SMB) outline with IPC7531-compliant footprint: pad length 5.84 mm, pad width 2.07 mm, spacing 2.60 mm. For thermal performance, ST recommends ≥1 cm² copper area under each lead to maintain Rth(j-a) ≤ 120 °C/W; doubling copper area reduces thermal resistance by ~30%, critical for sustained surge duty cycles.
SMBJ18CA-TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Package/Case:
- DO-214AA, SMB
- Series:
- SMBJ, 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:
- 29.2V
- Current - Peak Pulse (10/1000µs):
- 21.5A
- Power - Peak Pulse:
- 600W
- 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:
- SMB
SMBJ18CA-TR FAQ
1.How can I place an order for SMBJ18CA-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for SMBJ18CA-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 SMBJ18CA-TR reliable?
The price and inventory of SMBJ18CA-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMBJ18CA-TR is usually 5 days.
3.What payment methods are accepted for SMBJ18CA-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMBJ18CA-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMBJ18CA-TR?
SMBJ18CA-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMBJ18CA-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 SMBJ18CA-TR?
For technical support, including SMBJ18CA-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMBJ18CA-TR requirements.
6.How does Aetrix verify that SMBJ18CA-TR is sourced from the original manufacturer or authorized distributors?
All SMBJ18CA-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 SMBJ18CA-TR meets industry standards.
7.What is the process for return or replacement of SMBJ18CA-TR?
All SMBJ18CA-TR units undergo pre-shipment inspection (PSI). If there is an issue with SMBJ18CA-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 SMBJ18CA-TR part is unused and in its original packaging.
Return procedure for SMBJ18CA-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMBJ18CA-TR Tags
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Toshiba Semiconductor and Storage
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