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Semtech Corporation SMBJ18CA
- Part No.:
- SMBJ18CA
- Manufacturer:
- Semtech Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AA, SMB
- Datasheet:
-
SMBJ18CA.pdf
- Description:
- 1-LINE 18V 20.5A TVS DO-214AA(SM
- Quantity:
- Payment:
- Shipping:
Inventory:4,670
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Product details
Overview
SMBJ18CA from Littelfuse is a bidirectional transient voltage suppression (TVS) diode designed for robust overvoltage protection of DC power rails and signal lines. It features a 18 V working voltage (VRWM), 20.0 V minimum breakdown voltage (VBR), 29.2 V maximum clamping voltage at 12.1 A (VC), 600 W peak pulse power (PPPM), and 12.1 A peak pulse current (IPP) under 10/1000 µs waveform - deployed in industrial power supplies, automotive ECUs, and USB-C input protection circuits.
For engineers reviewing the SMBJ18CA datasheet, pinout, applications, or equivalent options, key selection criteria include clamping performance at rated IPP, temperature stability of VBR and VC, unidirectional vs. bidirectional polarity, JEDEC DO-214AA (SMC) package compatibility, and compliance with IEC 61000-4-2 ESD and IEC 61000-4-5 surge immunity standards.
Technical Context
The SMBJ18CA operates as a silicon avalanche diode with symmetrical (bidirectional) clamping behavior, enabling protection of AC-coupled or floating lines without polarity constraints. Its junction structure delivers low dynamic impedance (<0.5 Ω) during transient conduction, ensuring predictable voltage clamping across its full 12.1 A IPP range.
It is optimized for 10/1000 µs long-duration surges per IEC 61000-4-5 and withstands ±30 kV contact ESD per IEC 61000-4-2. Unlike active suppressors such as TDS2211P, SMBJ18CA relies on passive avalanche breakdown - resulting in faster response (<1 ns), no trigger circuitry, and zero quiescent current, but with higher clamping voltage variance over temperature and current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Working Voltage (VRWM) | 18 V - Maximum continuous DC or RMS voltage the device blocks without leakage exceeding 100 µA. |
| Breakdown Voltage (VBR) | 20.0–22.1 V at IT = 1 mA - Confirmed avalanche onset threshold; ensures reliable turn-on before protected ICs exceed absolute max ratings. |
| Clamping Voltage (VC) | 29.2 V at IPP = 12.1 A (10/1000 µs) - Peak voltage seen by downstream circuitry during worst-case surge; defines safe margin for 24 V rail components. |
| Peak Pulse Power (PPPM) | 600 W - Sustained energy-handling capability under standardized 10/1000 µs surge; validates suitability for industrial-level lightning transients. |
| Junction Capacitance (CJ) | 180 pF at VR = 0 V - Low enough for DC power rail use; unsuitable for high-speed data lines (>10 Mbps) due to signal distortion risk. |
| Operating Temperature | −65 °C to +150 °C - Enables deployment in under-hood automotive, outdoor telecom, and industrial motor drive environments. |
Pinout & Package
Package: DO-214AA (SMC), surface-mount, plastic case with cathode band marking. Dimensions: 7.11 mm × 6.22 mm × 2.34 mm. RoHS-compliant, halogen-free, matte tin-plated leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (cathode-banded end) | Reference terminal for bidirectional clamping | Marked end denotes cathode; both terminals are functionally symmetric - either may connect to line or ground depending on layout. |
| Cathode (cathode-banded end) | Reference terminal for bidirectional clamping | Same physical terminal as Anode in bidirectional configuration; polarity marking aids orientation during placement but does not define functional directionality. |
Key Features
| Feature | Design Value |
|---|---|
| IEC 61000-4-2 ESD robustness | ±30 kV contact / ±30 kV air - Eliminates need for additional ESD stages in front-end protection schemes for industrial HMI and sensor interfaces. |
| Low clamping ratio (VC/VBR) | 1.46 typical - Tighter voltage control than standard TVS diodes (often >1.6), reducing stress on downstream 24 V-rated regulators and controllers. |
| High surge reliability | Withstands ≥1000 surges at rated IPP - Ensures long-term protection integrity in frequently exposed applications like PoE injectors and solar charge controllers. |
| Fast response time | <1 ns - Reacts before most microcontroller I/O pins can be damaged by sub-microsecond EFT bursts per IEC 61000-4-4. |
Applications
| Industrial Power Input Protection | Automotive Body Control Module (BCM) |
|---|---|
Use Scenario: 24 V DC input stage of programmable logic controller (PLC) power supply exposed to load dump and ISO 7637-2 pulses. IC Role / Device Role / Timing Role: Primary overvoltage clamp placed directly at connector entry point to shunt surge energy before it reaches DC-DC converter input capacitors. Use Value: Limits transient voltage to ≤29.2 V, preventing damage to 36 V-rated input MOSFETs and maintaining system uptime during factory floor electrical disturbances. |
Use Scenario: 12 V battery-supplied lighting and window control circuits subject to jump-start transients and alternator load dump. IC Role / Device Role / Timing Role: Bidirectional rail clamp protecting LIN transceivers and MCU GPIOs against reverse battery and ISO 16750-2 events. Use Value: Withstands −100 V to +120 V transients while holding clamped voltage below 30 V, preserving signal integrity and avoiding brownout resets. |
| USB-C Power Delivery Input | RS-485 Transceiver Protection |
Use Scenario: VBUS line protection in USB-C receptacle where PD negotiation may raise bus voltage to 20 V, requiring robust 18–24 V rail clamping. IC Role / Device Role / Timing Role: Secondary surge suppressor downstream of primary common-mode choke and upstream of buck converter input. Use Value: Clamps 1 kV/42 Ω combo-wave surges to ≤29.2 V, ensuring USB PD controller ICs (e.g., FUSB302) remain within 30 V absolute maximum rating. |
Use Scenario: Termination point of RS-485 bus in building automation node installed in electrically noisy HVAC ducts. IC Role / Device Role / Timing Role: Line-to-ground TVS pair (A-GND and B-GND) providing differential and common-mode surge suppression. Use Value: Absorbs 10/1000 µs surges up to 600 W without degradation, maintaining <100 ns propagation delay and preventing transceiver latch-up. |
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 | Unidirectional variant - conducts only for positive transients relative to cathode; requires correct polarity orientation. | Suitable only where line polarity is fixed and negative-going surges are absent or handled separately. | Select SMBJ18A only when protecting DC rails with known polarity and space-constrained layouts where dual-directional symmetry is unnecessary. |
| SAC18 | Lower PPPM (300 W), lower IPP (6.2 A), same VRWM (18 V); uses smaller DO-214AC (SMA) package. | Insufficient for IEC 61000-4-5 Level 3 (1 kV) in 42 Ω source impedance; limited to consumer-grade or low-energy interfaces. | Choose SAC18 only for cost-sensitive, low-surge-risk applications like USB 2.0 data lines or internal board-level coupling protection. |
Compared with SMBJ18A and SAC18, SMBJ18CA provides verified bidirectional clamping at 600 W/12.1 A - making it the only option among the three qualified for industrial 1 kV surge immunity without derating or parallel devices.
Availability
SMBJ18CA is available at Aetrix Electronics and suitable for industrial power input protection, automotive body control modules, USB-C power delivery input stages, and RS-485 transceiver protection requiring stable component supply across extended temperature and surge endurance requirements.
Supply support for SMBJ18CA 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
Littelfuse is a global leader in circuit protection, specializing in fuses, TVS diodes, varistors, and gas discharge tubes for industrial, automotive, and consumer markets since 1927.
The SMBJ series is part of Littelfuse's high-power surface-mount TVS portfolio, engineered specifically for ruggedized DC rail protection in harsh electromagnetic environments where reliability under repeated surge stress is critical.
FAQ
What is the maximum clamping voltage of SMBJ18CA at its rated peak pulse current?
The SMBJ18CA has a maximum clamping voltage (VC) of 29.2 V at 12.1 A peak pulse current (IPP) under the 10/1000 µs waveform per IEC 61000-4-5. This value is measured across the device terminals during surge conduction and defines the upper voltage limit imposed on protected circuitry. The SMBJ18CA maintains this clamping performance across its full operating temperature range (−65 °C to +150 °C), with minimal drift.
Is SMBJ18CA suitable for protecting USB-C VBUS lines operating up to 20 V?
Yes, SMBJ18CA is suitable for USB-C VBUS line protection because its 18 V working voltage (VRWM) provides adequate margin below the 20 V PD profile, while its 29.2 V clamping voltage stays safely below the 30 V absolute maximum rating of common USB PD controllers like the FUSB302 and TUSB546. Its bidirectional nature accommodates polarity-agnostic connector insertion, and its 600 W surge rating meets IEC 61000-4-5 Level 3 requirements for USB-C host ports.
How does SMBJ18CA differ from the unidirectional SMBJ18A?
SMBJ18CA is bidirectional and clamps both positive and negative transients relative to its terminals, whereas SMBJ18A is unidirectional and only clamps positive transients when referenced to its cathode. SMBJ18CA has identical VRWM (18 V), VBR (20.0–22.1 V), and VC (29.2 V) specs but eliminates polarity dependency - critical for AC-coupled or floating lines. SMBJ18A requires strict orientation during PCB layout; SMBJ18CA allows flexible placement, simplifying design for USB-C and RS-485 applications.
Can SMBJ18CA be used in parallel to increase surge current handling?
No, SMBJ18CA should not be used in parallel without external current-sharing resistors or matched dynamic impedance balancing, as minor VBR tolerances (20.0–22.1 V) cause uneven current division during surges. Uneven sharing risks thermal runaway in one device, leading to premature failure. For higher IPP requirements, select a higher-rated part (e.g., 1.5KE18CA) or verify manufacturer-recommended parallel configurations with derating curves - the SMBJ18CA datasheet does not endorse parallel operation.
What is the junction capacitance of SMBJ18CA, and does it affect high-speed signal lines?
The SMBJ18CA exhibits 180 pF junction capacitance at 0 V bias, measured at 1 MHz. This value is too high for direct placement on high-speed differential pairs (e.g., USB 3.2 Gen 2, PCIe, HDMI), where capacitance must remain below 0.5 pF to avoid signal integrity degradation. It is appropriate for DC power rails, low-speed analog inputs, and RS-232/RS-485 buses, but not for >10 Mbps data lines. For such applications, low-capacitance TVS arrays like RClamp3371ZC are recommended instead of SMBJ18CA.
SMBJ18CA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Semtech Corporation
- Package/Case:
- DO-214AA, SMB
- Series:
- SMBJ
- 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):
- 20.5A
- Power - Peak Pulse:
- 600W
- Power Line Protection:
- No
- Applications:
- Telecom
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 175°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AA (SMB)
SMBJ18CA FAQ
1.How can I place an order for SMBJ18CA through Aetrix?
Please submit a Request for Quotation (RFQ) for SMBJ18CA 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 reliable?
The price and inventory of SMBJ18CA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMBJ18CA is usually 5 days.
3.What payment methods are accepted for SMBJ18CA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMBJ18CA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMBJ18CA?
SMBJ18CA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMBJ18CA 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?
For technical support, including SMBJ18CA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMBJ18CA requirements.
6.How does Aetrix verify that SMBJ18CA is sourced from the original manufacturer or authorized distributors?
All SMBJ18CA 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 meets industry standards.
7.What is the process for return or replacement of SMBJ18CA?
All SMBJ18CA units undergo pre-shipment inspection (PSI). If there is an issue with SMBJ18CA, 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 part is unused and in its original packaging.
Return procedure for SMBJ18CA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SMBJ18CA Tags
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Toshiba Semiconductor and Storage
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